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authorAkshay <[email protected]>2020-09-01 08:19:49 +0100
committerAkshay <[email protected]>2020-09-01 08:19:49 +0100
commitc9c8db0f308eb5dcb552d15ecfd403d623dc40de (patch)
treee88293873d5480fe2a932ade77cb9b610c53d3f4
parent70827fe44d6844528e7dd56637de2f0f3e0cf847 (diff)
new post: nixos
-rw-r--r--docs/index.html19
-rw-r--r--docs/index.xml794
-rw-r--r--docs/posts/auto-currying_rust_functions/index.html512
-rw-r--r--docs/posts/get_better_at_yanking_and_putting_in_vim/index.html2
-rw-r--r--docs/posts/gripes_with_go/index.html140
-rw-r--r--docs/posts/nixOS/index.html90
-rw-r--r--docs/posts/rapid_refactoring_with_vim/index.html50
-rw-r--r--docs/posts/static_sites_with_bash/index.html36
-rwxr-xr-xgenerate.sh8
-rw-r--r--posts/nixOS.md94
10 files changed, 989 insertions, 756 deletions
diff --git a/docs/index.html b/docs/index.html
index 6a70b78..ecc0fce 100644
--- a/docs/index.html
+++ b/docs/index.html
@@ -36,6 +36,23 @@
36 <tr> 36 <tr>
37 <td class=table-post> 37 <td class=table-post>
38 <div class="date"> 38 <div class="date">
39 01/09 — 2020
40 </div>
41 <a href="/posts/nixOS" class="post-link">
42 <span class="post-link">NixOS</span>
43 </a>
44 </td>
45 <td class=table-stats>
46 <span class="stats-number">
47 3.3
48 </span>
49 <span class=stats-unit>min</span>
50 </td>
51 </tr>
52
53 <tr>
54 <td class=table-post>
55 <div class="date">
39 01/08 — 2020 56 01/08 — 2020
40 </div> 57 </div>
41 <a href="/posts/gripes_with_go" class="post-link"> 58 <a href="/posts/gripes_with_go" class="post-link">
@@ -308,7 +325,7 @@
308 <tr> 325 <tr>
309 <td class=table-post> 326 <td class=table-post>
310 <div class="date"> 327 <div class="date">
311 29/07 — 2019 328 30/07 — 2019
312 </div> 329 </div>
313 <a href="/posts/get_better_at_yanking_and_putting_in_vim" class="post-link"> 330 <a href="/posts/get_better_at_yanking_and_putting_in_vim" class="post-link">
314 <span class="post-link">Get Better At Yanking And Putting In Vim</span> 331 <span class="post-link">Get Better At Yanking And Putting In Vim</span>
diff --git a/docs/index.xml b/docs/index.xml
index 003d4d6..d6f1ca7 100644
--- a/docs/index.xml
+++ b/docs/index.xml
@@ -12,6 +12,38 @@
12 <language>en-us</language> 12 <language>en-us</language>
13 <copyright>Creative Commons BY-NC-SA 4.0</copyright> 13 <copyright>Creative Commons BY-NC-SA 4.0</copyright>
14 <item> 14 <item>
15<title>NixOS</title>
16<description>&lt;p&gt;I have been eyeing operating systems with functional package managers for a while now, aka, NixOS or Guix. Reproducible builds, declarative and rollback-able system configuration, system consistency, all sound pretty cool. I have been using NixOS for about a month now.&lt;/p&gt;
17&lt;h3 id="installation"&gt;Installation&lt;/h3&gt;
18&lt;p&gt;I went with their minimal installation ISO. The installation was pretty smooth from start to end, no hitches there. The entire &lt;a href="https://nixos.org/manual/nixos/stable/"&gt;manual&lt;/a&gt; is available offline, and is accessible during the installation. Very handy.&lt;/p&gt;
19&lt;h3 id="setup"&gt;Setup&lt;/h3&gt;
20&lt;p&gt;The entire system is configured via &lt;code&gt;/etc/nixos/configuration.nix&lt;/code&gt;. Wifi, &lt;code&gt;libinput&lt;/code&gt; gestures, audio, locale settings, there are options for literally everything. You can declaratively write down the packages you want installed too. With fresh installs of most distros, I usually fumble with getting things like screen backlight and media keys to work. If I do manage to fix it, I can’t carry it forward to future installations trivially. Getting all my hardware to work on NixOS is as easy as:&lt;/p&gt;
21&lt;pre&gt;&lt;code&gt;{
22 server.xserver.libinput.enable = true; # touchpad
23 programs.light.enable = true; # backlight
24 hardware.pulseaudio.enable = true; # audio
25 networking.wireless.enable = true; # wifi
26}&lt;/code&gt;&lt;/pre&gt;
27&lt;h3 id="developing-with-nix"&gt;Developing with Nix&lt;/h3&gt;
28&lt;p&gt;Nix makes it easy to enter environments that aren’t affected by your system configuration using &lt;code&gt;nix-shell&lt;/code&gt;.&lt;/p&gt;
29&lt;p&gt;Builds may be generated by specifying a &lt;code&gt;default.nix&lt;/code&gt; file, and running &lt;code&gt;nix-build&lt;/code&gt;. Conventional package managers require you to specify a dependency list, but there is no guarantee that this list is complete. The package will build on your machine even if you forget a dependency. However, with Nix, packages are installed to &lt;code&gt;/nix/store&lt;/code&gt;, and not global paths such as &lt;code&gt;/usr/bin/...&lt;/code&gt;, if your project builds, it means you have included every last one.&lt;/p&gt;
30&lt;p&gt;Issues on most my projects have been “unable to build because &lt;code&gt;libxcb&lt;/code&gt; is missing”, or “this version of &lt;code&gt;openssl&lt;/code&gt; is too old”. Tools like &lt;code&gt;cargo&lt;/code&gt; and &lt;code&gt;pip&lt;/code&gt; are poor package managers. While they &lt;em&gt;can&lt;/em&gt; guarantee that Rust or Python dependencies are met, they make assumptions about the target system.&lt;/p&gt;
31&lt;p&gt;For example, &lt;a href="https://github.com/nerdypepper/site"&gt;this website&lt;/a&gt; is now built using Nix, anyone using Nix may simply, clone the repository and run &lt;code&gt;./generate.sh&lt;/code&gt;, and it would &lt;em&gt;just work&lt;/em&gt;, while keeping your global namespace clean™:&lt;/p&gt;
32&lt;div class="sourceCode" id="cb2"&gt;&lt;pre class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb2-1"&gt;&lt;a href="#cb2-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;#! /usr/bin/env nix-shell&lt;/span&gt;&lt;/span&gt;
33&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2"&gt;&lt;/a&gt;&lt;span class="co"&gt;#! nix-shell -i bash -p eva pandoc esh&lt;/span&gt;&lt;/span&gt;
34&lt;span id="cb2-3"&gt;&lt;a href="#cb2-3"&gt;&lt;/a&gt;&lt;/span&gt;
35&lt;span id="cb2-4"&gt;&lt;a href="#cb2-4"&gt;&lt;/a&gt;&lt;span class="co"&gt;# some bash magic ;)&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
36&lt;p&gt;Dependencies are included with the &lt;code&gt;-p&lt;/code&gt; flag, the shell script is executed with an interpreter, specified with the &lt;code&gt;-i&lt;/code&gt; flag.&lt;/p&gt;
37&lt;h3 id="impressions"&gt;Impressions&lt;/h3&gt;
38&lt;p&gt;NixOS is by no means, simple. As a newcomer, using Nix was not easy, heck, I had to learn a purely functional, lazy language to just build programs. There is a lot to be desired on the tooling front as well. A well fleshed out LSP plugin would be nice (&lt;a href="https://github.com/nix-community/rnix-lsp"&gt;rnix-lsp looks promising&lt;/a&gt;).&lt;/p&gt;
39&lt;p&gt;Being able to rollback changes at a system level is cool. Package broke something? Just &lt;code&gt;nixos-rebuild switch --rollback&lt;/code&gt;! Deleted &lt;code&gt;nix&lt;/code&gt; by mistake? Find the binary in &lt;code&gt;/nix/store&lt;/code&gt; and rollback! You aren’t punished for not thinking twice.&lt;/p&gt;
40&lt;p&gt;I don’t see myself switching to anything else in the near future, NixOS does a lot of things right. If I ever need to reinstall NixOS, I can generate an &lt;a href="https://github.com/nix-community/nixos-generators"&gt;image of my current system&lt;/a&gt;.&lt;/p&gt;
41&lt;p&gt;&lt;a href="https://u.peppe.rs/6m.png"&gt;&lt;img src="https://u.peppe.rs/6m.png" /&gt;&lt;/a&gt;&lt;/p&gt;</description>
42<link>https://peppe.rs/posts/nixOS/</link>
43<pubDate>Tue, 01 Sep 2020 07:08:00 +0000</pubDate>
44<guid>https://peppe.rs/posts/nixOS/</guid>
45</item>
46<item>
15<title>Gripes With Go</title> 47<title>Gripes With Go</title>
16<description>&lt;p&gt;You’ve read a lot of posts about the shortcomings of the Go programming language, so what’s one more.&lt;/p&gt; 48<description>&lt;p&gt;You’ve read a lot of posts about the shortcomings of the Go programming language, so what’s one more.&lt;/p&gt;
17&lt;ol type="1"&gt; 49&lt;ol type="1"&gt;
@@ -25,101 +57,101 @@
25&lt;h3 id="lack-of-sum-types"&gt;Lack of Sum types&lt;/h3&gt; 57&lt;h3 id="lack-of-sum-types"&gt;Lack of Sum types&lt;/h3&gt;
26&lt;p&gt;A “Sum” type is a data type that can hold one of many states at a given time, similar to how a boolean can hold a true or a false, not too different from an &lt;code&gt;enum&lt;/code&gt; type in C. Go lacks &lt;code&gt;enum&lt;/code&gt; types unfortunately, and you are forced to resort to crafting your own substitute.&lt;/p&gt; 58&lt;p&gt;A “Sum” type is a data type that can hold one of many states at a given time, similar to how a boolean can hold a true or a false, not too different from an &lt;code&gt;enum&lt;/code&gt; type in C. Go lacks &lt;code&gt;enum&lt;/code&gt; types unfortunately, and you are forced to resort to crafting your own substitute.&lt;/p&gt;
27&lt;p&gt;A type to represent gender for example:&lt;/p&gt; 59&lt;p&gt;A type to represent gender for example:&lt;/p&gt;
28&lt;div class="sourceCode" id="cb1"&gt;&lt;pre class="sourceCode go"&gt;&lt;code class="sourceCode go"&gt;&lt;span id="cb1-1"&gt;&lt;a href="#cb1-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; Gender &lt;span class="dt"&gt;int&lt;/span&gt;&lt;/span&gt; 60&lt;div class="sourceCode" id="cb1"&gt;&lt;pre class="sourceCode go"&gt;&lt;code class="sourceCode go"&gt;&lt;span id="cb1-1"&gt;&lt;a href="#cb1-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; Gender &lt;span class="dt"&gt;int&lt;/span&gt;&lt;/span&gt;
29&lt;span id="cb1-2"&gt;&lt;a href="#cb1-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 61&lt;span id="cb1-2"&gt;&lt;a href="#cb1-2"&gt;&lt;/a&gt;&lt;/span&gt;
30&lt;span id="cb1-3"&gt;&lt;a href="#cb1-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;const&lt;/span&gt; (&lt;/span&gt; 62&lt;span id="cb1-3"&gt;&lt;a href="#cb1-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;const&lt;/span&gt; (&lt;/span&gt;
31&lt;span id="cb1-4"&gt;&lt;a href="#cb1-4" aria-hidden="true"&gt;&lt;/a&gt; Male Gender = &lt;span class="ot"&gt;iota&lt;/span&gt; &lt;span class="co"&gt;// assigns Male to 0&lt;/span&gt;&lt;/span&gt; 63&lt;span id="cb1-4"&gt;&lt;a href="#cb1-4"&gt;&lt;/a&gt; Male Gender = &lt;span class="ot"&gt;iota&lt;/span&gt; &lt;span class="co"&gt;// assigns Male to 0&lt;/span&gt;&lt;/span&gt;
32&lt;span id="cb1-5"&gt;&lt;a href="#cb1-5" aria-hidden="true"&gt;&lt;/a&gt; Female &lt;span class="co"&gt;// assigns Female to 1&lt;/span&gt;&lt;/span&gt; 64&lt;span id="cb1-5"&gt;&lt;a href="#cb1-5"&gt;&lt;/a&gt; Female &lt;span class="co"&gt;// assigns Female to 1&lt;/span&gt;&lt;/span&gt;
33&lt;span id="cb1-6"&gt;&lt;a href="#cb1-6" aria-hidden="true"&gt;&lt;/a&gt; Other &lt;span class="co"&gt;// assigns Other to 2&lt;/span&gt;&lt;/span&gt; 65&lt;span id="cb1-6"&gt;&lt;a href="#cb1-6"&gt;&lt;/a&gt; Other &lt;span class="co"&gt;// assigns Other to 2&lt;/span&gt;&lt;/span&gt;
34&lt;span id="cb1-7"&gt;&lt;a href="#cb1-7" aria-hidden="true"&gt;&lt;/a&gt;)&lt;/span&gt; 66&lt;span id="cb1-7"&gt;&lt;a href="#cb1-7"&gt;&lt;/a&gt;)&lt;/span&gt;
35&lt;span id="cb1-8"&gt;&lt;a href="#cb1-8" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 67&lt;span id="cb1-8"&gt;&lt;a href="#cb1-8"&gt;&lt;/a&gt;&lt;/span&gt;
36&lt;span id="cb1-9"&gt;&lt;a href="#cb1-9" aria-hidden="true"&gt;&lt;/a&gt;fmt.Println(&lt;span class="st"&gt;&amp;quot;My gender is &amp;quot;&lt;/span&gt;, Male)&lt;/span&gt; 68&lt;span id="cb1-9"&gt;&lt;a href="#cb1-9"&gt;&lt;/a&gt;fmt.Println(&lt;span class="st"&gt;&amp;quot;My gender is &amp;quot;&lt;/span&gt;, Male)&lt;/span&gt;
37&lt;span id="cb1-10"&gt;&lt;a href="#cb1-10" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// My gender is 0&lt;/span&gt;&lt;/span&gt; 69&lt;span id="cb1-10"&gt;&lt;a href="#cb1-10"&gt;&lt;/a&gt;&lt;span class="co"&gt;// My gender is 0&lt;/span&gt;&lt;/span&gt;
38&lt;span id="cb1-11"&gt;&lt;a href="#cb1-11" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// Oops! We have to implement String() for Gender ...&lt;/span&gt;&lt;/span&gt; 70&lt;span id="cb1-11"&gt;&lt;a href="#cb1-11"&gt;&lt;/a&gt;&lt;span class="co"&gt;// Oops! We have to implement String() for Gender ...&lt;/span&gt;&lt;/span&gt;
39&lt;span id="cb1-12"&gt;&lt;a href="#cb1-12" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 71&lt;span id="cb1-12"&gt;&lt;a href="#cb1-12"&gt;&lt;/a&gt;&lt;/span&gt;
40&lt;span id="cb1-13"&gt;&lt;a href="#cb1-13" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;func&lt;/span&gt; (g Gender) String() &lt;span class="dt"&gt;string&lt;/span&gt; {&lt;/span&gt; 72&lt;span id="cb1-13"&gt;&lt;a href="#cb1-13"&gt;&lt;/a&gt;&lt;span class="kw"&gt;func&lt;/span&gt; (g Gender) String() &lt;span class="dt"&gt;string&lt;/span&gt; {&lt;/span&gt;
41&lt;span id="cb1-14"&gt;&lt;a href="#cb1-14" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;switch&lt;/span&gt; (g) {&lt;/span&gt; 73&lt;span id="cb1-14"&gt;&lt;a href="#cb1-14"&gt;&lt;/a&gt; &lt;span class="kw"&gt;switch&lt;/span&gt; (g) {&lt;/span&gt;
42&lt;span id="cb1-15"&gt;&lt;a href="#cb1-15" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;case&lt;/span&gt; &lt;span class="dv"&gt;0&lt;/span&gt;: &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;Male&amp;quot;&lt;/span&gt;&lt;/span&gt; 74&lt;span id="cb1-15"&gt;&lt;a href="#cb1-15"&gt;&lt;/a&gt; &lt;span class="kw"&gt;case&lt;/span&gt; &lt;span class="dv"&gt;0&lt;/span&gt;: &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;Male&amp;quot;&lt;/span&gt;&lt;/span&gt;
43&lt;span id="cb1-16"&gt;&lt;a href="#cb1-16" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;case&lt;/span&gt; &lt;span class="dv"&gt;1&lt;/span&gt;: &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;Female&amp;quot;&lt;/span&gt;&lt;/span&gt; 75&lt;span id="cb1-16"&gt;&lt;a href="#cb1-16"&gt;&lt;/a&gt; &lt;span class="kw"&gt;case&lt;/span&gt; &lt;span class="dv"&gt;1&lt;/span&gt;: &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;Female&amp;quot;&lt;/span&gt;&lt;/span&gt;
44&lt;span id="cb1-17"&gt;&lt;a href="#cb1-17" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;default&lt;/span&gt;: &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;Other&amp;quot;&lt;/span&gt;&lt;/span&gt; 76&lt;span id="cb1-17"&gt;&lt;a href="#cb1-17"&gt;&lt;/a&gt; &lt;span class="kw"&gt;default&lt;/span&gt;: &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;Other&amp;quot;&lt;/span&gt;&lt;/span&gt;
45&lt;span id="cb1-18"&gt;&lt;a href="#cb1-18" aria-hidden="true"&gt;&lt;/a&gt; }&lt;/span&gt; 77&lt;span id="cb1-18"&gt;&lt;a href="#cb1-18"&gt;&lt;/a&gt; }&lt;/span&gt;
46&lt;span id="cb1-19"&gt;&lt;a href="#cb1-19" aria-hidden="true"&gt;&lt;/a&gt;}&lt;/span&gt; 78&lt;span id="cb1-19"&gt;&lt;a href="#cb1-19"&gt;&lt;/a&gt;}&lt;/span&gt;
47&lt;span id="cb1-20"&gt;&lt;a href="#cb1-20" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 79&lt;span id="cb1-20"&gt;&lt;a href="#cb1-20"&gt;&lt;/a&gt;&lt;/span&gt;
48&lt;span id="cb1-21"&gt;&lt;a href="#cb1-21" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// You can accidentally do stupid stuff like:&lt;/span&gt;&lt;/span&gt; 80&lt;span id="cb1-21"&gt;&lt;a href="#cb1-21"&gt;&lt;/a&gt;&lt;span class="co"&gt;// You can accidentally do stupid stuff like:&lt;/span&gt;&lt;/span&gt;
49&lt;span id="cb1-22"&gt;&lt;a href="#cb1-22" aria-hidden="true"&gt;&lt;/a&gt;gender := Male + &lt;span class="dv"&gt;1&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 81&lt;span id="cb1-22"&gt;&lt;a href="#cb1-22"&gt;&lt;/a&gt;gender := Male + &lt;span class="dv"&gt;1&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
50&lt;p&gt;The Haskell equivalent of the same:&lt;/p&gt; 82&lt;p&gt;The Haskell equivalent of the same:&lt;/p&gt;
51&lt;div class="sourceCode" id="cb2"&gt;&lt;pre class="sourceCode haskell"&gt;&lt;code class="sourceCode haskell"&gt;&lt;span id="cb2-1"&gt;&lt;a href="#cb2-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;data&lt;/span&gt; &lt;span class="dt"&gt;Gender&lt;/span&gt; &lt;span class="ot"&gt;=&lt;/span&gt; &lt;span class="dt"&gt;Male&lt;/span&gt;&lt;/span&gt; 83&lt;div class="sourceCode" id="cb2"&gt;&lt;pre class="sourceCode haskell"&gt;&lt;code class="sourceCode haskell"&gt;&lt;span id="cb2-1"&gt;&lt;a href="#cb2-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;data&lt;/span&gt; &lt;span class="dt"&gt;Gender&lt;/span&gt; &lt;span class="ot"&gt;=&lt;/span&gt; &lt;span class="dt"&gt;Male&lt;/span&gt;&lt;/span&gt;
52&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;|&lt;/span&gt; &lt;span class="dt"&gt;Female&lt;/span&gt;&lt;/span&gt; 84&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2"&gt;&lt;/a&gt; &lt;span class="op"&gt;|&lt;/span&gt; &lt;span class="dt"&gt;Female&lt;/span&gt;&lt;/span&gt;
53&lt;span id="cb2-3"&gt;&lt;a href="#cb2-3" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;|&lt;/span&gt; &lt;span class="dt"&gt;Other&lt;/span&gt;&lt;/span&gt; 85&lt;span id="cb2-3"&gt;&lt;a href="#cb2-3"&gt;&lt;/a&gt; &lt;span class="op"&gt;|&lt;/span&gt; &lt;span class="dt"&gt;Other&lt;/span&gt;&lt;/span&gt;
54&lt;span id="cb2-4"&gt;&lt;a href="#cb2-4" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;deriving&lt;/span&gt; (&lt;span class="dt"&gt;Show&lt;/span&gt;)&lt;/span&gt; 86&lt;span id="cb2-4"&gt;&lt;a href="#cb2-4"&gt;&lt;/a&gt; &lt;span class="kw"&gt;deriving&lt;/span&gt; (&lt;span class="dt"&gt;Show&lt;/span&gt;)&lt;/span&gt;
55&lt;span id="cb2-5"&gt;&lt;a href="#cb2-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 87&lt;span id="cb2-5"&gt;&lt;a href="#cb2-5"&gt;&lt;/a&gt;&lt;/span&gt;
56&lt;span id="cb2-6"&gt;&lt;a href="#cb2-6" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="fu"&gt;print&lt;/span&gt; &lt;span class="op"&gt;$&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;My gender is &amp;quot;&lt;/span&gt; &lt;span class="op"&gt;++&lt;/span&gt; (&lt;span class="fu"&gt;show&lt;/span&gt; &lt;span class="dt"&gt;Male&lt;/span&gt;)&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 88&lt;span id="cb2-6"&gt;&lt;a href="#cb2-6"&gt;&lt;/a&gt;&lt;span class="fu"&gt;print&lt;/span&gt; &lt;span class="op"&gt;$&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;My gender is &amp;quot;&lt;/span&gt; &lt;span class="op"&gt;++&lt;/span&gt; (&lt;span class="fu"&gt;show&lt;/span&gt; &lt;span class="dt"&gt;Male&lt;/span&gt;)&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
57&lt;h3 id="type-assertions"&gt;Type Assertions&lt;/h3&gt; 89&lt;h3 id="type-assertions"&gt;Type Assertions&lt;/h3&gt;
58&lt;p&gt;A downcast with an optional error check? What could go wrong?&lt;/p&gt; 90&lt;p&gt;A downcast with an optional error check? What could go wrong?&lt;/p&gt;
59&lt;p&gt;Type assertions in Go allow you to do:&lt;/p&gt; 91&lt;p&gt;Type assertions in Go allow you to do:&lt;/p&gt;
60&lt;div class="sourceCode" id="cb3"&gt;&lt;pre class="sourceCode go"&gt;&lt;code class="sourceCode go"&gt;&lt;span id="cb3-1"&gt;&lt;a href="#cb3-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;var&lt;/span&gt; x &lt;span class="kw"&gt;interface&lt;/span&gt;{} = &lt;span class="dv"&gt;7&lt;/span&gt;&lt;/span&gt; 92&lt;div class="sourceCode" id="cb3"&gt;&lt;pre class="sourceCode go"&gt;&lt;code class="sourceCode go"&gt;&lt;span id="cb3-1"&gt;&lt;a href="#cb3-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;var&lt;/span&gt; x &lt;span class="kw"&gt;interface&lt;/span&gt;{} = &lt;span class="dv"&gt;7&lt;/span&gt;&lt;/span&gt;
61&lt;span id="cb3-2"&gt;&lt;a href="#cb3-2" aria-hidden="true"&gt;&lt;/a&gt;y, goodToGo := x.(&lt;span class="dt"&gt;int&lt;/span&gt;)&lt;/span&gt; 93&lt;span id="cb3-2"&gt;&lt;a href="#cb3-2"&gt;&lt;/a&gt;y, goodToGo := x.(&lt;span class="dt"&gt;int&lt;/span&gt;)&lt;/span&gt;
62&lt;span id="cb3-3"&gt;&lt;a href="#cb3-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;if&lt;/span&gt; goodToGo {&lt;/span&gt; 94&lt;span id="cb3-3"&gt;&lt;a href="#cb3-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;if&lt;/span&gt; goodToGo {&lt;/span&gt;
63&lt;span id="cb3-4"&gt;&lt;a href="#cb3-4" aria-hidden="true"&gt;&lt;/a&gt; fmt.Println(y)&lt;/span&gt; 95&lt;span id="cb3-4"&gt;&lt;a href="#cb3-4"&gt;&lt;/a&gt; fmt.Println(y)&lt;/span&gt;
64&lt;span id="cb3-5"&gt;&lt;a href="#cb3-5" aria-hidden="true"&gt;&lt;/a&gt;}&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 96&lt;span id="cb3-5"&gt;&lt;a href="#cb3-5"&gt;&lt;/a&gt;}&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
65&lt;p&gt;The error check however is optional:&lt;/p&gt; 97&lt;p&gt;The error check however is optional:&lt;/p&gt;
66&lt;div class="sourceCode" id="cb4"&gt;&lt;pre class="sourceCode go"&gt;&lt;code class="sourceCode go"&gt;&lt;span id="cb4-1"&gt;&lt;a href="#cb4-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;var&lt;/span&gt; x &lt;span class="kw"&gt;interface&lt;/span&gt;{} = &lt;span class="dv"&gt;7&lt;/span&gt;&lt;/span&gt; 98&lt;div class="sourceCode" id="cb4"&gt;&lt;pre class="sourceCode go"&gt;&lt;code class="sourceCode go"&gt;&lt;span id="cb4-1"&gt;&lt;a href="#cb4-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;var&lt;/span&gt; x &lt;span class="kw"&gt;interface&lt;/span&gt;{} = &lt;span class="dv"&gt;7&lt;/span&gt;&lt;/span&gt;
67&lt;span id="cb4-2"&gt;&lt;a href="#cb4-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;var&lt;/span&gt; y := x.(&lt;span class="dt"&gt;float64&lt;/span&gt;)&lt;/span&gt; 99&lt;span id="cb4-2"&gt;&lt;a href="#cb4-2"&gt;&lt;/a&gt;&lt;span class="kw"&gt;var&lt;/span&gt; y := x.(&lt;span class="dt"&gt;float64&lt;/span&gt;)&lt;/span&gt;
68&lt;span id="cb4-3"&gt;&lt;a href="#cb4-3" aria-hidden="true"&gt;&lt;/a&gt;fmt.Println(y)&lt;/span&gt; 100&lt;span id="cb4-3"&gt;&lt;a href="#cb4-3"&gt;&lt;/a&gt;fmt.Println(y)&lt;/span&gt;
69&lt;span id="cb4-4"&gt;&lt;a href="#cb4-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// results in a runtime error:&lt;/span&gt;&lt;/span&gt; 101&lt;span id="cb4-4"&gt;&lt;a href="#cb4-4"&gt;&lt;/a&gt;&lt;span class="co"&gt;// results in a runtime error:&lt;/span&gt;&lt;/span&gt;
70&lt;span id="cb4-5"&gt;&lt;a href="#cb4-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// panic: interface conversion: interface {} is int, not float64&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 102&lt;span id="cb4-5"&gt;&lt;a href="#cb4-5"&gt;&lt;/a&gt;&lt;span class="co"&gt;// panic: interface conversion: interface {} is int, not float64&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
71&lt;h3 id="date-and-time"&gt;Date and Time&lt;/h3&gt; 103&lt;h3 id="date-and-time"&gt;Date and Time&lt;/h3&gt;
72&lt;p&gt;Anyone that has written Go previously, will probably already know what I am getting at here. For the uninitiated, parsing and formatting dates in Go requires a “layout”. This “layout” is based on magical reference date:&lt;/p&gt; 104&lt;p&gt;Anyone that has written Go previously, will probably already know what I am getting at here. For the uninitiated, parsing and formatting dates in Go requires a “layout”. This “layout” is based on magical reference date:&lt;/p&gt;
73&lt;pre&gt;&lt;code&gt;Mon Jan 2 15:04:05 MST 2006&lt;/code&gt;&lt;/pre&gt; 105&lt;pre&gt;&lt;code&gt;Mon Jan 2 15:04:05 MST 2006&lt;/code&gt;&lt;/pre&gt;
74&lt;p&gt;Which is the date produced when you write the first seven natural numbers like so:&lt;/p&gt; 106&lt;p&gt;Which is the date produced when you write the first seven natural numbers like so:&lt;/p&gt;
75&lt;pre&gt;&lt;code&gt;01/02 03:04:05 &amp;#39;06 -0700&lt;/code&gt;&lt;/pre&gt; 107&lt;pre&gt;&lt;code&gt;01/02 03:04:05 &amp;#39;06 -0700&lt;/code&gt;&lt;/pre&gt;
76&lt;p&gt;Parsing a string in &lt;code&gt;YYYY-MM-DD&lt;/code&gt; format would look something like:&lt;/p&gt; 108&lt;p&gt;Parsing a string in &lt;code&gt;YYYY-MM-DD&lt;/code&gt; format would look something like:&lt;/p&gt;
77&lt;div class="sourceCode" id="cb7"&gt;&lt;pre class="sourceCode go"&gt;&lt;code class="sourceCode go"&gt;&lt;span id="cb7-1"&gt;&lt;a href="#cb7-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;const&lt;/span&gt; layout = &lt;span class="st"&gt;&amp;quot;2006-01-02&amp;quot;&lt;/span&gt;&lt;/span&gt; 109&lt;div class="sourceCode" id="cb7"&gt;&lt;pre class="sourceCode go"&gt;&lt;code class="sourceCode go"&gt;&lt;span id="cb7-1"&gt;&lt;a href="#cb7-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;const&lt;/span&gt; layout = &lt;span class="st"&gt;&amp;quot;2006-01-02&amp;quot;&lt;/span&gt;&lt;/span&gt;
78&lt;span id="cb7-2"&gt;&lt;a href="#cb7-2" aria-hidden="true"&gt;&lt;/a&gt;time.Parse(layout, &lt;span class="st"&gt;&amp;quot;2020-08-01&amp;quot;&lt;/span&gt;)&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 110&lt;span id="cb7-2"&gt;&lt;a href="#cb7-2"&gt;&lt;/a&gt;time.Parse(layout, &lt;span class="st"&gt;&amp;quot;2020-08-01&amp;quot;&lt;/span&gt;)&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
79&lt;p&gt;This so-called “intuitive” method of formatting dates doesn’t allow you to print &lt;code&gt;0000 hrs&lt;/code&gt; as &lt;code&gt;2400 hrs&lt;/code&gt;, it doesn’t allow you to omit the leading zero in 24 hour formats. It is rife with inconveniences, if only there were a &lt;a href="https://man7.org/linux/man-pages/man3/strftime.3.html"&gt;tried and tested&lt;/a&gt; date formatting convention …&lt;/p&gt; 111&lt;p&gt;This so-called “intuitive” method of formatting dates doesn’t allow you to print &lt;code&gt;0000 hrs&lt;/code&gt; as &lt;code&gt;2400 hrs&lt;/code&gt;, it doesn’t allow you to omit the leading zero in 24 hour formats. It is rife with inconveniences, if only there were a &lt;a href="https://man7.org/linux/man-pages/man3/strftime.3.html"&gt;tried and tested&lt;/a&gt; date formatting convention …&lt;/p&gt;
80&lt;h3 id="statements-over-expressions"&gt;Statements over Expressions&lt;/h3&gt; 112&lt;h3 id="statements-over-expressions"&gt;Statements over Expressions&lt;/h3&gt;
81&lt;p&gt;Statements have side effects, expressions return values. More often than not, expressions are easier to understand at a glance: evaluate the LHS and assign the same to the RHS.&lt;/p&gt; 113&lt;p&gt;Statements have side effects, expressions return values. More often than not, expressions are easier to understand at a glance: evaluate the LHS and assign the same to the RHS.&lt;/p&gt;
82&lt;p&gt;Rust allows you to create local namespaces, and treats blocks (&lt;code&gt;{}&lt;/code&gt;) as expressions:&lt;/p&gt; 114&lt;p&gt;Rust allows you to create local namespaces, and treats blocks (&lt;code&gt;{}&lt;/code&gt;) as expressions:&lt;/p&gt;
83&lt;div class="sourceCode" id="cb8"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb8-1"&gt;&lt;a href="#cb8-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; twenty_seven &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 115&lt;div class="sourceCode" id="cb8"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb8-1"&gt;&lt;a href="#cb8-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; twenty_seven = &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
84&lt;span id="cb8-2"&gt;&lt;a href="#cb8-2" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; three &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="dv"&gt;1&lt;/span&gt; &lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="dv"&gt;2&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 116&lt;span id="cb8-2"&gt;&lt;a href="#cb8-2"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; three = &lt;span class="dv"&gt;1&lt;/span&gt; + &lt;span class="dv"&gt;2&lt;/span&gt;;&lt;/span&gt;
85&lt;span id="cb8-3"&gt;&lt;a href="#cb8-3" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; nine &lt;span class="op"&gt;=&lt;/span&gt; three &lt;span class="op"&gt;*&lt;/span&gt; three&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 117&lt;span id="cb8-3"&gt;&lt;a href="#cb8-3"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; nine = three * three;&lt;/span&gt;
86&lt;span id="cb8-4"&gt;&lt;a href="#cb8-4" aria-hidden="true"&gt;&lt;/a&gt; nine &lt;span class="op"&gt;*&lt;/span&gt; three&lt;/span&gt; 118&lt;span id="cb8-4"&gt;&lt;a href="#cb8-4"&gt;&lt;/a&gt; nine * three&lt;/span&gt;
87&lt;span id="cb8-5"&gt;&lt;a href="#cb8-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 119&lt;span id="cb8-5"&gt;&lt;a href="#cb8-5"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
88&lt;p&gt;The Go equivalent of the same:&lt;/p&gt; 120&lt;p&gt;The Go equivalent of the same:&lt;/p&gt;
89&lt;div class="sourceCode" id="cb9"&gt;&lt;pre class="sourceCode go"&gt;&lt;code class="sourceCode go"&gt;&lt;span id="cb9-1"&gt;&lt;a href="#cb9-1" aria-hidden="true"&gt;&lt;/a&gt;twenty_seven := &lt;span class="ot"&gt;nil&lt;/span&gt;&lt;/span&gt; 121&lt;div class="sourceCode" id="cb9"&gt;&lt;pre class="sourceCode go"&gt;&lt;code class="sourceCode go"&gt;&lt;span id="cb9-1"&gt;&lt;a href="#cb9-1"&gt;&lt;/a&gt;twenty_seven := &lt;span class="ot"&gt;nil&lt;/span&gt;&lt;/span&gt;
90&lt;span id="cb9-2"&gt;&lt;a href="#cb9-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 122&lt;span id="cb9-2"&gt;&lt;a href="#cb9-2"&gt;&lt;/a&gt;&lt;/span&gt;
91&lt;span id="cb9-3"&gt;&lt;a href="#cb9-3" aria-hidden="true"&gt;&lt;/a&gt;three := &lt;span class="dv"&gt;1&lt;/span&gt; + &lt;span class="dv"&gt;2&lt;/span&gt;&lt;/span&gt; 123&lt;span id="cb9-3"&gt;&lt;a href="#cb9-3"&gt;&lt;/a&gt;three := &lt;span class="dv"&gt;1&lt;/span&gt; + &lt;span class="dv"&gt;2&lt;/span&gt;&lt;/span&gt;
92&lt;span id="cb9-4"&gt;&lt;a href="#cb9-4" aria-hidden="true"&gt;&lt;/a&gt;nine := three * three&lt;/span&gt; 124&lt;span id="cb9-4"&gt;&lt;a href="#cb9-4"&gt;&lt;/a&gt;nine := three * three&lt;/span&gt;
93&lt;span id="cb9-5"&gt;&lt;a href="#cb9-5" aria-hidden="true"&gt;&lt;/a&gt;twenty_seven = nine * three&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 125&lt;span id="cb9-5"&gt;&lt;a href="#cb9-5"&gt;&lt;/a&gt;twenty_seven = nine * three&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
94&lt;h3 id="erroring-out-on-unused-variables"&gt;Erroring out on unused variables&lt;/h3&gt; 126&lt;h3 id="erroring-out-on-unused-variables"&gt;Erroring out on unused variables&lt;/h3&gt;
95&lt;p&gt;Want to quickly prototype something? Go says no! In all seriousness, a warning would suffice, I don’t want to have to go back and comment each unused import out, only to come back and uncomment them a few seconds later.&lt;/p&gt; 127&lt;p&gt;Want to quickly prototype something? Go says no! In all seriousness, a warning would suffice, I don’t want to have to go back and comment each unused import out, only to come back and uncomment them a few seconds later.&lt;/p&gt;
96&lt;h3 id="error-handling"&gt;Error handling&lt;/h3&gt; 128&lt;h3 id="error-handling"&gt;Error handling&lt;/h3&gt;
97&lt;div class="sourceCode" id="cb10"&gt;&lt;pre class="sourceCode go"&gt;&lt;code class="sourceCode go"&gt;&lt;span id="cb10-1"&gt;&lt;a href="#cb10-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;if&lt;/span&gt; err != &lt;span class="ot"&gt;nil&lt;/span&gt; { ... }&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 129&lt;div class="sourceCode" id="cb10"&gt;&lt;pre class="sourceCode go"&gt;&lt;code class="sourceCode go"&gt;&lt;span id="cb10-1"&gt;&lt;a href="#cb10-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;if&lt;/span&gt; err != &lt;span class="ot"&gt;nil&lt;/span&gt; { ... }&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
98&lt;p&gt;Need I say more? I will, for good measure:&lt;/p&gt; 130&lt;p&gt;Need I say more? I will, for good measure:&lt;/p&gt;
99&lt;ol type="1"&gt; 131&lt;ol type="1"&gt;
100&lt;li&gt;Error handling is optional&lt;/li&gt; 132&lt;li&gt;Error handling is optional&lt;/li&gt;
101&lt;li&gt;Errors are propagated via a clunky &lt;code&gt;if&lt;/code&gt; + &lt;code&gt;return&lt;/code&gt; statement&lt;/li&gt; 133&lt;li&gt;Errors are propagated via a clunky &lt;code&gt;if&lt;/code&gt; + &lt;code&gt;return&lt;/code&gt; statement&lt;/li&gt;
102&lt;/ol&gt; 134&lt;/ol&gt;
103&lt;p&gt;I prefer Haskell’s “Monadic” error handling, which is employed by Rust as well:&lt;/p&gt; 135&lt;p&gt;I prefer Haskell’s “Monadic” error handling, which is employed by Rust as well:&lt;/p&gt;
104&lt;div class="sourceCode" id="cb11"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb11-1"&gt;&lt;a href="#cb11-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// 1. error handling is compulsory&lt;/span&gt;&lt;/span&gt; 136&lt;div class="sourceCode" id="cb11"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb11-1"&gt;&lt;a href="#cb11-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// 1. error handling is compulsory&lt;/span&gt;&lt;/span&gt;
105&lt;span id="cb11-2"&gt;&lt;a href="#cb11-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// 2. errors are propagated with the `?` operator&lt;/span&gt;&lt;/span&gt; 137&lt;span id="cb11-2"&gt;&lt;a href="#cb11-2"&gt;&lt;/a&gt;&lt;span class="co"&gt;// 2. errors are propagated with the `?` operator&lt;/span&gt;&lt;/span&gt;
106&lt;span id="cb11-3"&gt;&lt;a href="#cb11-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; foo() &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;Result&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;&lt;span class="dt"&gt;String&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; &lt;span class="pp"&gt;io::&lt;/span&gt;&lt;span class="bu"&gt;Error&lt;/span&gt;&lt;span class="op"&gt;&amp;gt;&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 138&lt;span id="cb11-3"&gt;&lt;a href="#cb11-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; foo() -&amp;gt; &lt;span class="dt"&gt;Result&lt;/span&gt;&amp;lt;&lt;span class="dt"&gt;String&lt;/span&gt;, &lt;span class="pp"&gt;io::&lt;/span&gt;Error&amp;gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
107&lt;span id="cb11-4"&gt;&lt;a href="#cb11-4" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; &lt;span class="kw"&gt;mut&lt;/span&gt; f &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="pp"&gt;File::&lt;/span&gt;open(&lt;span class="st"&gt;&amp;quot;foo.txt&amp;quot;&lt;/span&gt;)&lt;span class="op"&gt;?;&lt;/span&gt; &lt;span class="co"&gt;// return if error&lt;/span&gt;&lt;/span&gt; 139&lt;span id="cb11-4"&gt;&lt;a href="#cb11-4"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; &lt;span class="kw"&gt;mut&lt;/span&gt; f = &lt;span class="pp"&gt;File::&lt;/span&gt;open(&lt;span class="st"&gt;&amp;quot;foo.txt&amp;quot;&lt;/span&gt;)?; &lt;span class="co"&gt;// return if error&lt;/span&gt;&lt;/span&gt;
108&lt;span id="cb11-5"&gt;&lt;a href="#cb11-5" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; &lt;span class="kw"&gt;mut&lt;/span&gt; s &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="dt"&gt;String&lt;/span&gt;&lt;span class="pp"&gt;::&lt;/span&gt;new()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 140&lt;span id="cb11-5"&gt;&lt;a href="#cb11-5"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; &lt;span class="kw"&gt;mut&lt;/span&gt; s = &lt;span class="dt"&gt;String&lt;/span&gt;::new();&lt;/span&gt;
109&lt;span id="cb11-6"&gt;&lt;a href="#cb11-6" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 141&lt;span id="cb11-6"&gt;&lt;a href="#cb11-6"&gt;&lt;/a&gt;&lt;/span&gt;
110&lt;span id="cb11-7"&gt;&lt;a href="#cb11-7" aria-hidden="true"&gt;&lt;/a&gt; f&lt;span class="op"&gt;.&lt;/span&gt;read_to_string(&lt;span class="op"&gt;&amp;amp;&lt;/span&gt;&lt;span class="kw"&gt;mut&lt;/span&gt; s)&lt;span class="op"&gt;?;&lt;/span&gt; &lt;span class="co"&gt;// return if error&lt;/span&gt;&lt;/span&gt; 142&lt;span id="cb11-7"&gt;&lt;a href="#cb11-7"&gt;&lt;/a&gt; f.read_to_string(&amp;amp;&lt;span class="kw"&gt;mut&lt;/span&gt; s)?; &lt;span class="co"&gt;// return if error&lt;/span&gt;&lt;/span&gt;
111&lt;span id="cb11-8"&gt;&lt;a href="#cb11-8" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 143&lt;span id="cb11-8"&gt;&lt;a href="#cb11-8"&gt;&lt;/a&gt;&lt;/span&gt;
112&lt;span id="cb11-9"&gt;&lt;a href="#cb11-9" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="cn"&gt;Ok&lt;/span&gt;(s) &lt;span class="co"&gt;// all good, return a string inside a `Result` context&lt;/span&gt;&lt;/span&gt; 144&lt;span id="cb11-9"&gt;&lt;a href="#cb11-9"&gt;&lt;/a&gt; &lt;span class="cn"&gt;Ok&lt;/span&gt;(s) &lt;span class="co"&gt;// all good, return a string inside a `Result` context&lt;/span&gt;&lt;/span&gt;
113&lt;span id="cb11-10"&gt;&lt;a href="#cb11-10" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 145&lt;span id="cb11-10"&gt;&lt;a href="#cb11-10"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
114&lt;span id="cb11-11"&gt;&lt;a href="#cb11-11" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 146&lt;span id="cb11-11"&gt;&lt;a href="#cb11-11"&gt;&lt;/a&gt;&lt;/span&gt;
115&lt;span id="cb11-12"&gt;&lt;a href="#cb11-12" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; main() &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 147&lt;span id="cb11-12"&gt;&lt;a href="#cb11-12"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; main() &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
116&lt;span id="cb11-13"&gt;&lt;a href="#cb11-13" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="co"&gt;// `contents` is an enum known as Result:&lt;/span&gt;&lt;/span&gt; 148&lt;span id="cb11-13"&gt;&lt;a href="#cb11-13"&gt;&lt;/a&gt; &lt;span class="co"&gt;// `contents` is an enum known as Result:&lt;/span&gt;&lt;/span&gt;
117&lt;span id="cb11-14"&gt;&lt;a href="#cb11-14" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; contents &lt;span class="op"&gt;=&lt;/span&gt; foo()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 149&lt;span id="cb11-14"&gt;&lt;a href="#cb11-14"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; contents = foo();&lt;/span&gt;
118&lt;span id="cb11-15"&gt;&lt;a href="#cb11-15" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;match&lt;/span&gt; contents &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 150&lt;span id="cb11-15"&gt;&lt;a href="#cb11-15"&gt;&lt;/a&gt; &lt;span class="kw"&gt;match&lt;/span&gt; contents &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
119&lt;span id="cb11-16"&gt;&lt;a href="#cb11-16" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="cn"&gt;Ok&lt;/span&gt;(c) &lt;span class="op"&gt;=&amp;gt;&lt;/span&gt; &lt;span class="pp"&gt;println!&lt;/span&gt;(c)&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt; 151&lt;span id="cb11-16"&gt;&lt;a href="#cb11-16"&gt;&lt;/a&gt; &lt;span class="cn"&gt;Ok&lt;/span&gt;(c) =&amp;gt; &lt;span class="pp"&gt;println!&lt;/span&gt;(c),&lt;/span&gt;
120&lt;span id="cb11-17"&gt;&lt;a href="#cb11-17" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="cn"&gt;Err&lt;/span&gt;(e) &lt;span class="op"&gt;=&amp;gt;&lt;/span&gt; &lt;span class="pp"&gt;eprintln!&lt;/span&gt;(e)&lt;/span&gt; 152&lt;span id="cb11-17"&gt;&lt;a href="#cb11-17"&gt;&lt;/a&gt; &lt;span class="cn"&gt;Err&lt;/span&gt;(e) =&amp;gt; &lt;span class="pp"&gt;eprintln!&lt;/span&gt;(e)&lt;/span&gt;
121&lt;span id="cb11-18"&gt;&lt;a href="#cb11-18" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 153&lt;span id="cb11-18"&gt;&lt;a href="#cb11-18"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
122&lt;span id="cb11-19"&gt;&lt;a href="#cb11-19" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 154&lt;span id="cb11-19"&gt;&lt;a href="#cb11-19"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
123&lt;h3 id="conclusion"&gt;Conclusion&lt;/h3&gt; 155&lt;h3 id="conclusion"&gt;Conclusion&lt;/h3&gt;
124&lt;p&gt;I did not want to conclude without talking about stylistic choices, lack of metaprogramming, bizzare export rules, but, I am too busy converting my &lt;code&gt;interface{}&lt;/code&gt; types into actual generic code for Go v2.&lt;/p&gt;</description> 156&lt;p&gt;I did not want to conclude without talking about stylistic choices, lack of metaprogramming, bizzare export rules, but, I am too busy converting my &lt;code&gt;interface{}&lt;/code&gt; types into actual generic code for Go v2.&lt;/p&gt;</description>
125<link>https://peppe.rs/posts/gripes_with_go/</link> 157<link>https://peppe.rs/posts/gripes_with_go/</link>
@@ -138,7 +170,7 @@
138&lt;p&gt;Rust performs compile-time type inference. The type checker, in turn, compiles and infers types, I would describe it as a compiler inside a compiler. It is possible that &lt;code&gt;rustc&lt;/code&gt; may never finish compiling your Rust program! I lied, &lt;code&gt;rustc&lt;/code&gt; stops after a while, after hitting the recursion limit.&lt;/p&gt; 170&lt;p&gt;Rust performs compile-time type inference. The type checker, in turn, compiles and infers types, I would describe it as a compiler inside a compiler. It is possible that &lt;code&gt;rustc&lt;/code&gt; may never finish compiling your Rust program! I lied, &lt;code&gt;rustc&lt;/code&gt; stops after a while, after hitting the recursion limit.&lt;/p&gt;
139&lt;p&gt;I understand that this post lacks content.&lt;/p&gt;</description> 171&lt;p&gt;I understand that this post lacks content.&lt;/p&gt;</description>
140<link>https://peppe.rs/posts/turing_complete_type_systems/</link> 172<link>https://peppe.rs/posts/turing_complete_type_systems/</link>
141<pubDate>Thu, 18 Jun 2020 05:18:00 +0000</pubDate> 173<pubDate>Wed, 17 Jun 2020 18:30:00 +0000</pubDate>
142<guid>https://peppe.rs/posts/turing_complete_type_systems/</guid> 174<guid>https://peppe.rs/posts/turing_complete_type_systems/</guid>
143</item> 175</item>
144<item> 176<item>
@@ -199,17 +231,17 @@ h(x)(y)(z) = g(y)(z) = k(z) = v&lt;/code&gt;&lt;/pre&gt;
199&lt;p&gt;We will be using Attribute macros to convert a Rust function into a curried Rust function, which we should be able to call via: &lt;code&gt;function(arg1)(arg2)&lt;/code&gt;.&lt;/p&gt; 231&lt;p&gt;We will be using Attribute macros to convert a Rust function into a curried Rust function, which we should be able to call via: &lt;code&gt;function(arg1)(arg2)&lt;/code&gt;.&lt;/p&gt;
200&lt;h3 id="definitions"&gt;Definitions&lt;/h3&gt; 232&lt;h3 id="definitions"&gt;Definitions&lt;/h3&gt;
201&lt;p&gt;Being respectable programmers, we define the input to and the output from our proc-macro. Here’s a good non-trivial function to start out with:&lt;/p&gt; 233&lt;p&gt;Being respectable programmers, we define the input to and the output from our proc-macro. Here’s a good non-trivial function to start out with:&lt;/p&gt;
202&lt;div class="sourceCode" id="cb4"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb4-1"&gt;&lt;a href="#cb4-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add(x&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; y&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; z&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 234&lt;div class="sourceCode" id="cb4"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb4-1"&gt;&lt;a href="#cb4-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add(x: &lt;span class="dt"&gt;u32&lt;/span&gt;, y: &lt;span class="dt"&gt;u32&lt;/span&gt;, z: &lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
203&lt;span id="cb4-2"&gt;&lt;a href="#cb4-2" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; x &lt;span class="op"&gt;+&lt;/span&gt; y &lt;span class="op"&gt;+&lt;/span&gt; z&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 235&lt;span id="cb4-2"&gt;&lt;a href="#cb4-2"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; x + y + z;&lt;/span&gt;
204&lt;span id="cb4-3"&gt;&lt;a href="#cb4-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 236&lt;span id="cb4-3"&gt;&lt;a href="#cb4-3"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
205&lt;p&gt;Hmm, what would our output look like? What should our proc-macro generate ideally? Well, if we understood currying correctly, we should accept an argument and return a function that accepts an argument and returns … you get the point. Something like this should do:&lt;/p&gt; 237&lt;p&gt;Hmm, what would our output look like? What should our proc-macro generate ideally? Well, if we understood currying correctly, we should accept an argument and return a function that accepts an argument and returns … you get the point. Something like this should do:&lt;/p&gt;
206&lt;div class="sourceCode" id="cb5"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb5-1"&gt;&lt;a href="#cb5-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add_curried1(x&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="op"&gt;?&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 238&lt;div class="sourceCode" id="cb5"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb5-1"&gt;&lt;a href="#cb5-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add_curried1(x: &lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; ? &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
207&lt;span id="cb5-2"&gt;&lt;a href="#cb5-2" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="kw"&gt;fn&lt;/span&gt; add_curried2 (y&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="op"&gt;?&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 239&lt;span id="cb5-2"&gt;&lt;a href="#cb5-2"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="kw"&gt;fn&lt;/span&gt; add_curried2 (y: &lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; ? &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
208&lt;span id="cb5-3"&gt;&lt;a href="#cb5-3" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="kw"&gt;fn&lt;/span&gt; add_curried3 (z&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 240&lt;span id="cb5-3"&gt;&lt;a href="#cb5-3"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="kw"&gt;fn&lt;/span&gt; add_curried3 (z: &lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
209&lt;span id="cb5-4"&gt;&lt;a href="#cb5-4" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; x &lt;span class="op"&gt;+&lt;/span&gt; y &lt;span class="op"&gt;+&lt;/span&gt; z&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 241&lt;span id="cb5-4"&gt;&lt;a href="#cb5-4"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; x + y + z;&lt;/span&gt;
210&lt;span id="cb5-5"&gt;&lt;a href="#cb5-5" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 242&lt;span id="cb5-5"&gt;&lt;a href="#cb5-5"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
211&lt;span id="cb5-6"&gt;&lt;a href="#cb5-6" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 243&lt;span id="cb5-6"&gt;&lt;a href="#cb5-6"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
212&lt;span id="cb5-7"&gt;&lt;a href="#cb5-7" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 244&lt;span id="cb5-7"&gt;&lt;a href="#cb5-7"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
213&lt;p&gt;A couple of things to note:&lt;/p&gt; 245&lt;p&gt;A couple of things to note:&lt;/p&gt;
214&lt;p&gt;&lt;strong&gt;Return types&lt;/strong&gt;&lt;br /&gt; 246&lt;p&gt;&lt;strong&gt;Return types&lt;/strong&gt;&lt;br /&gt;
215We have placed &lt;code&gt;?&lt;/code&gt;s in place of return types. Let’s try to fix that. &lt;code&gt;add_curried3&lt;/code&gt; returns the ‘value’, so &lt;code&gt;u32&lt;/code&gt; is accurate. &lt;code&gt;add_curried2&lt;/code&gt; returns &lt;code&gt;add_curried3&lt;/code&gt;. What is the type of &lt;code&gt;add_curried3&lt;/code&gt;? It is a function that takes in a &lt;code&gt;u32&lt;/code&gt; and returns a &lt;code&gt;u32&lt;/code&gt;. So a &lt;code&gt;fn(u32) -&amp;gt; u32&lt;/code&gt; will do right? No, I’ll explain why in the next point, but for now, we will make use of the &lt;code&gt;Fn&lt;/code&gt; trait, our return type is &lt;code&gt;impl Fn(u32) -&amp;gt; u32&lt;/code&gt;. This basically tells the compiler that we will be returning something function-like, a.k.a, behaves like a &lt;code&gt;Fn&lt;/code&gt;. Cool!&lt;/p&gt; 247We have placed &lt;code&gt;?&lt;/code&gt;s in place of return types. Let’s try to fix that. &lt;code&gt;add_curried3&lt;/code&gt; returns the ‘value’, so &lt;code&gt;u32&lt;/code&gt; is accurate. &lt;code&gt;add_curried2&lt;/code&gt; returns &lt;code&gt;add_curried3&lt;/code&gt;. What is the type of &lt;code&gt;add_curried3&lt;/code&gt;? It is a function that takes in a &lt;code&gt;u32&lt;/code&gt; and returns a &lt;code&gt;u32&lt;/code&gt;. So a &lt;code&gt;fn(u32) -&amp;gt; u32&lt;/code&gt; will do right? No, I’ll explain why in the next point, but for now, we will make use of the &lt;code&gt;Fn&lt;/code&gt; trait, our return type is &lt;code&gt;impl Fn(u32) -&amp;gt; u32&lt;/code&gt;. This basically tells the compiler that we will be returning something function-like, a.k.a, behaves like a &lt;code&gt;Fn&lt;/code&gt;. Cool!&lt;/p&gt;
@@ -222,9 +254,9 @@ We have placed &lt;code&gt;?&lt;/code&gt;s in place of return types. Let’s try
222A function cannot access it’s environment. Our solution will not work. &lt;code&gt;add_curried3&lt;/code&gt; attempts to access &lt;code&gt;x&lt;/code&gt;, which is not allowed! A closure&lt;a href="#fn1" class="footnote-ref" id="fnref1" role="doc-noteref"&gt;&lt;sup&gt;1&lt;/sup&gt;&lt;/a&gt; however, can. If we are returning a closure, our return type must be &lt;code&gt;impl Fn&lt;/code&gt;, and not &lt;code&gt;fn&lt;/code&gt;. The difference between the &lt;code&gt;Fn&lt;/code&gt; trait and function pointers is beyond the scope of this post.&lt;/p&gt; 254A function cannot access it’s environment. Our solution will not work. &lt;code&gt;add_curried3&lt;/code&gt; attempts to access &lt;code&gt;x&lt;/code&gt;, which is not allowed! A closure&lt;a href="#fn1" class="footnote-ref" id="fnref1" role="doc-noteref"&gt;&lt;sup&gt;1&lt;/sup&gt;&lt;/a&gt; however, can. If we are returning a closure, our return type must be &lt;code&gt;impl Fn&lt;/code&gt;, and not &lt;code&gt;fn&lt;/code&gt;. The difference between the &lt;code&gt;Fn&lt;/code&gt; trait and function pointers is beyond the scope of this post.&lt;/p&gt;
223&lt;h3 id="refinement"&gt;Refinement&lt;/h3&gt; 255&lt;h3 id="refinement"&gt;Refinement&lt;/h3&gt;
224&lt;p&gt;Armed with knowledge, we refine our expected output, this time, employing closures:&lt;/p&gt; 256&lt;p&gt;Armed with knowledge, we refine our expected output, this time, employing closures:&lt;/p&gt;
225&lt;div class="sourceCode" id="cb8"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb8-1"&gt;&lt;a href="#cb8-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add(x&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 257&lt;div class="sourceCode" id="cb8"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb8-1"&gt;&lt;a href="#cb8-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add(x: &lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
226&lt;span id="cb8-2"&gt;&lt;a href="#cb8-2" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="kw"&gt;move&lt;/span&gt; &lt;span class="op"&gt;|&lt;/span&gt;y&lt;span class="op"&gt;|&lt;/span&gt; &lt;span class="kw"&gt;move&lt;/span&gt; &lt;span class="op"&gt;|&lt;/span&gt;z&lt;span class="op"&gt;|&lt;/span&gt; x &lt;span class="op"&gt;+&lt;/span&gt; y &lt;span class="op"&gt;+&lt;/span&gt; z&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 258&lt;span id="cb8-2"&gt;&lt;a href="#cb8-2"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="kw"&gt;move&lt;/span&gt; |y| &lt;span class="kw"&gt;move&lt;/span&gt; |z| x + y + z;&lt;/span&gt;
227&lt;span id="cb8-3"&gt;&lt;a href="#cb8-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 259&lt;span id="cb8-3"&gt;&lt;a href="#cb8-3"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
228&lt;p&gt;Alas, that does not compile either! It errors out with the following message:&lt;/p&gt; 260&lt;p&gt;Alas, that does not compile either! It errors out with the following message:&lt;/p&gt;
229&lt;pre&gt;&lt;code&gt;error[E0562]: `impl Trait` not allowed outside of function 261&lt;pre&gt;&lt;code&gt;error[E0562]: `impl Trait` not allowed outside of function
230and inherent method return types 262and inherent method return types
@@ -235,15 +267,15 @@ and inherent method return types
235&lt;/code&gt;&lt;/pre&gt; 267&lt;/code&gt;&lt;/pre&gt;
236&lt;p&gt;You are allowed to return an &lt;code&gt;impl Fn&lt;/code&gt; only inside a function. We are currently returning it from another return! Or at least, that was the most I could make out of the error message.&lt;/p&gt; 268&lt;p&gt;You are allowed to return an &lt;code&gt;impl Fn&lt;/code&gt; only inside a function. We are currently returning it from another return! Or at least, that was the most I could make out of the error message.&lt;/p&gt;
237&lt;p&gt;We are going to have to cheat a bit to fix this issue; with type aliases and a convenient nightly feature &lt;a href="#fn2" class="footnote-ref" id="fnref2" role="doc-noteref"&gt;&lt;sup&gt;2&lt;/sup&gt;&lt;/a&gt;:&lt;/p&gt; 269&lt;p&gt;We are going to have to cheat a bit to fix this issue; with type aliases and a convenient nightly feature &lt;a href="#fn2" class="footnote-ref" id="fnref2" role="doc-noteref"&gt;&lt;sup&gt;2&lt;/sup&gt;&lt;/a&gt;:&lt;/p&gt;
238&lt;div class="sourceCode" id="cb10"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb10-1"&gt;&lt;a href="#cb10-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="at"&gt;#![&lt;/span&gt;feature&lt;span class="at"&gt;(&lt;/span&gt;type_alias_impl_trait&lt;span class="at"&gt;)]&lt;/span&gt; &lt;span class="co"&gt;// allows us to use `impl Fn` in type aliases!&lt;/span&gt;&lt;/span&gt; 270&lt;div class="sourceCode" id="cb10"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb10-1"&gt;&lt;a href="#cb10-1"&gt;&lt;/a&gt;&lt;span class="at"&gt;#![&lt;/span&gt;feature&lt;span class="at"&gt;(&lt;/span&gt;type_alias_impl_trait&lt;span class="at"&gt;)]&lt;/span&gt; &lt;span class="co"&gt;// allows us to use `impl Fn` in type aliases!&lt;/span&gt;&lt;/span&gt;
239&lt;span id="cb10-2"&gt;&lt;a href="#cb10-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 271&lt;span id="cb10-2"&gt;&lt;a href="#cb10-2"&gt;&lt;/a&gt;&lt;/span&gt;
240&lt;span id="cb10-3"&gt;&lt;a href="#cb10-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt; &lt;span class="co"&gt;// the return value when zero args are to be applied&lt;/span&gt;&lt;/span&gt; 272&lt;span id="cb10-3"&gt;&lt;a href="#cb10-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 = &lt;span class="dt"&gt;u32&lt;/span&gt;; &lt;span class="co"&gt;// the return value when zero args are to be applied&lt;/span&gt;&lt;/span&gt;
241&lt;span id="cb10-4"&gt;&lt;a href="#cb10-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T1 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; T0&lt;span class="op"&gt;;&lt;/span&gt; &lt;span class="co"&gt;// the return value when one arg is to be applied&lt;/span&gt;&lt;/span&gt; 273&lt;span id="cb10-4"&gt;&lt;a href="#cb10-4"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T1 = &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; T0; &lt;span class="co"&gt;// the return value when one arg is to be applied&lt;/span&gt;&lt;/span&gt;
242&lt;span id="cb10-5"&gt;&lt;a href="#cb10-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T2 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; T1&lt;span class="op"&gt;;&lt;/span&gt; &lt;span class="co"&gt;// the return value when two args are to be applied&lt;/span&gt;&lt;/span&gt; 274&lt;span id="cb10-5"&gt;&lt;a href="#cb10-5"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T2 = &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; T1; &lt;span class="co"&gt;// the return value when two args are to be applied&lt;/span&gt;&lt;/span&gt;
243&lt;span id="cb10-6"&gt;&lt;a href="#cb10-6" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 275&lt;span id="cb10-6"&gt;&lt;a href="#cb10-6"&gt;&lt;/a&gt;&lt;/span&gt;
244&lt;span id="cb10-7"&gt;&lt;a href="#cb10-7" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add(x&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; T2 &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 276&lt;span id="cb10-7"&gt;&lt;a href="#cb10-7"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add(x: &lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; T2 &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
245&lt;span id="cb10-8"&gt;&lt;a href="#cb10-8" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="kw"&gt;move&lt;/span&gt; &lt;span class="op"&gt;|&lt;/span&gt;y&lt;span class="op"&gt;|&lt;/span&gt; &lt;span class="kw"&gt;move&lt;/span&gt; &lt;span class="op"&gt;|&lt;/span&gt;z&lt;span class="op"&gt;|&lt;/span&gt; x &lt;span class="op"&gt;+&lt;/span&gt; y &lt;span class="op"&gt;+&lt;/span&gt; z&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 277&lt;span id="cb10-8"&gt;&lt;a href="#cb10-8"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="kw"&gt;move&lt;/span&gt; |y| &lt;span class="kw"&gt;move&lt;/span&gt; |z| x + y + z;&lt;/span&gt;
246&lt;span id="cb10-9"&gt;&lt;a href="#cb10-9" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 278&lt;span id="cb10-9"&gt;&lt;a href="#cb10-9"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
247&lt;p&gt;Drop that into a cargo project, call &lt;code&gt;add(4)(5)(6)&lt;/code&gt;, cross your fingers, and run &lt;code&gt;cargo +nightly run&lt;/code&gt;. You should see a 15 unless you forgot to print it!&lt;/p&gt; 279&lt;p&gt;Drop that into a cargo project, call &lt;code&gt;add(4)(5)(6)&lt;/code&gt;, cross your fingers, and run &lt;code&gt;cargo +nightly run&lt;/code&gt;. You should see a 15 unless you forgot to print it!&lt;/p&gt;
248&lt;h3 id="the-in-betweens"&gt;The In-Betweens&lt;/h3&gt; 280&lt;h3 id="the-in-betweens"&gt;The In-Betweens&lt;/h3&gt;
249&lt;p&gt;Let us write the magical bits that take us from function to curried function.&lt;/p&gt; 281&lt;p&gt;Let us write the magical bits that take us from function to curried function.&lt;/p&gt;
@@ -277,19 +309,19 @@ proc-macro = true # this is important!&lt;/code&gt;&lt;/pre&gt;
277&lt;p&gt;We will be using an external &lt;code&gt;proc-macro2&lt;/code&gt; crate as well as an internal &lt;code&gt;proc-macro&lt;/code&gt; crate. Not confusing at all!&lt;/p&gt; 309&lt;p&gt;We will be using an external &lt;code&gt;proc-macro2&lt;/code&gt; crate as well as an internal &lt;code&gt;proc-macro&lt;/code&gt; crate. Not confusing at all!&lt;/p&gt;
278&lt;h4 id="the-attribute-macro"&gt;The attribute macro&lt;/h4&gt; 310&lt;h4 id="the-attribute-macro"&gt;The attribute macro&lt;/h4&gt;
279&lt;p&gt;Drop this into &lt;code&gt;src/lib.rs&lt;/code&gt;, to get the ball rolling.&lt;/p&gt; 311&lt;p&gt;Drop this into &lt;code&gt;src/lib.rs&lt;/code&gt;, to get the ball rolling.&lt;/p&gt;
280&lt;div class="sourceCode" id="cb13"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb13-1"&gt;&lt;a href="#cb13-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt; 312&lt;div class="sourceCode" id="cb13"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb13-1"&gt;&lt;a href="#cb13-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
281&lt;span id="cb13-2"&gt;&lt;a href="#cb13-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 313&lt;span id="cb13-2"&gt;&lt;a href="#cb13-2"&gt;&lt;/a&gt;&lt;/span&gt;
282&lt;span id="cb13-3"&gt;&lt;a href="#cb13-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;proc_macro::&lt;/span&gt;TokenStream&lt;span class="op"&gt;;&lt;/span&gt; &lt;span class="co"&gt;// 1&lt;/span&gt;&lt;/span&gt; 314&lt;span id="cb13-3"&gt;&lt;a href="#cb13-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;proc_macro::&lt;/span&gt;TokenStream; &lt;span class="co"&gt;// 1&lt;/span&gt;&lt;/span&gt;
283&lt;span id="cb13-4"&gt;&lt;a href="#cb13-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;quote::&lt;/span&gt;quote&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 315&lt;span id="cb13-4"&gt;&lt;a href="#cb13-4"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;quote::&lt;/span&gt;quote;&lt;/span&gt;
284&lt;span id="cb13-5"&gt;&lt;a href="#cb13-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;syn::&lt;/span&gt;&lt;span class="op"&gt;{&lt;/span&gt;parse_macro_input&lt;span class="op"&gt;,&lt;/span&gt; ItemFn&lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt; 316&lt;span id="cb13-5"&gt;&lt;a href="#cb13-5"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;syn::&lt;/span&gt;&lt;span class="op"&gt;{&lt;/span&gt;parse_macro_input, ItemFn&lt;span class="op"&gt;}&lt;/span&gt;;&lt;/span&gt;
285&lt;span id="cb13-6"&gt;&lt;a href="#cb13-6" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 317&lt;span id="cb13-6"&gt;&lt;a href="#cb13-6"&gt;&lt;/a&gt;&lt;/span&gt;
286&lt;span id="cb13-7"&gt;&lt;a href="#cb13-7" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;proc_macro_attribute&lt;span class="at"&gt;]&lt;/span&gt; &lt;span class="co"&gt;// 2&lt;/span&gt;&lt;/span&gt; 318&lt;span id="cb13-7"&gt;&lt;a href="#cb13-7"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;proc_macro_attribute&lt;span class="at"&gt;]&lt;/span&gt; &lt;span class="co"&gt;// 2&lt;/span&gt;&lt;/span&gt;
287&lt;span id="cb13-8"&gt;&lt;a href="#cb13-8" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;pub&lt;/span&gt; &lt;span class="kw"&gt;fn&lt;/span&gt; curry(_attr&lt;span class="op"&gt;:&lt;/span&gt; TokenStream&lt;span class="op"&gt;,&lt;/span&gt; item&lt;span class="op"&gt;:&lt;/span&gt; TokenStream) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; TokenStream &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 319&lt;span id="cb13-8"&gt;&lt;a href="#cb13-8"&gt;&lt;/a&gt;&lt;span class="kw"&gt;pub&lt;/span&gt; &lt;span class="kw"&gt;fn&lt;/span&gt; curry(_attr: TokenStream, item: TokenStream) -&amp;gt; TokenStream &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
288&lt;span id="cb13-9"&gt;&lt;a href="#cb13-9" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; parsed &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="pp"&gt;parse_macro_input!&lt;/span&gt;(item &lt;span class="kw"&gt;as&lt;/span&gt; ItemFn)&lt;span class="op"&gt;;&lt;/span&gt; &lt;span class="co"&gt;// 3&lt;/span&gt;&lt;/span&gt; 320&lt;span id="cb13-9"&gt;&lt;a href="#cb13-9"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; parsed = &lt;span class="pp"&gt;parse_macro_input!&lt;/span&gt;(item &lt;span class="kw"&gt;as&lt;/span&gt; ItemFn); &lt;span class="co"&gt;// 3&lt;/span&gt;&lt;/span&gt;
289&lt;span id="cb13-10"&gt;&lt;a href="#cb13-10" aria-hidden="true"&gt;&lt;/a&gt; generate_curry(parsed)&lt;span class="op"&gt;.&lt;/span&gt;into() &lt;span class="co"&gt;// 4&lt;/span&gt;&lt;/span&gt; 321&lt;span id="cb13-10"&gt;&lt;a href="#cb13-10"&gt;&lt;/a&gt; generate_curry(parsed).into() &lt;span class="co"&gt;// 4&lt;/span&gt;&lt;/span&gt;
290&lt;span id="cb13-11"&gt;&lt;a href="#cb13-11" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 322&lt;span id="cb13-11"&gt;&lt;a href="#cb13-11"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
291&lt;span id="cb13-12"&gt;&lt;a href="#cb13-12" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 323&lt;span id="cb13-12"&gt;&lt;a href="#cb13-12"&gt;&lt;/a&gt;&lt;/span&gt;
292&lt;span id="cb13-13"&gt;&lt;a href="#cb13-13" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; generate_curry(parsed&lt;span class="op"&gt;:&lt;/span&gt; ItemFn) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="pp"&gt;proc_macro2::&lt;/span&gt;TokenStream &lt;span class="op"&gt;{}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 324&lt;span id="cb13-13"&gt;&lt;a href="#cb13-13"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; generate_curry(parsed: ItemFn) -&amp;gt; &lt;span class="pp"&gt;proc_macro2::&lt;/span&gt;TokenStream &lt;span class="op"&gt;{}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
293&lt;p&gt;&lt;strong&gt;1. Imports&lt;/strong&gt;&lt;/p&gt; 325&lt;p&gt;&lt;strong&gt;1. Imports&lt;/strong&gt;&lt;/p&gt;
294&lt;p&gt;A &lt;code&gt;Tokenstream&lt;/code&gt; holds (hopefully valid) Rust code, this is the type of our input and output. Note that we are importing this type from &lt;code&gt;proc_macro&lt;/code&gt; and not &lt;code&gt;proc_macro2&lt;/code&gt;.&lt;/p&gt; 326&lt;p&gt;A &lt;code&gt;Tokenstream&lt;/code&gt; holds (hopefully valid) Rust code, this is the type of our input and output. Note that we are importing this type from &lt;code&gt;proc_macro&lt;/code&gt; and not &lt;code&gt;proc_macro2&lt;/code&gt;.&lt;/p&gt;
295&lt;p&gt;&lt;code&gt;quote!&lt;/code&gt; from the &lt;code&gt;quote&lt;/code&gt; crate is a macro that allows us to quickly produce &lt;code&gt;TokenStream&lt;/code&gt;s. Much like the LISP &lt;code&gt;quote&lt;/code&gt; procedure, you can use the &lt;code&gt;quote!&lt;/code&gt; macro for symbolic transformations.&lt;/p&gt; 327&lt;p&gt;&lt;code&gt;quote!&lt;/code&gt; from the &lt;code&gt;quote&lt;/code&gt; crate is a macro that allows us to quickly produce &lt;code&gt;TokenStream&lt;/code&gt;s. Much like the LISP &lt;code&gt;quote&lt;/code&gt; procedure, you can use the &lt;code&gt;quote!&lt;/code&gt; macro for symbolic transformations.&lt;/p&gt;
@@ -301,16 +333,16 @@ proc-macro = true # this is important!&lt;/code&gt;&lt;/pre&gt;
301&lt;p&gt;&lt;strong&gt;4. Returning &lt;code&gt;TokenStream&lt;/code&gt;s &lt;/strong&gt;&lt;/p&gt; 333&lt;p&gt;&lt;strong&gt;4. Returning &lt;code&gt;TokenStream&lt;/code&gt;s &lt;/strong&gt;&lt;/p&gt;
302&lt;p&gt;We haven’t filled in &lt;code&gt;generate_curry&lt;/code&gt; yet, but we can see that it returns a &lt;code&gt;proc_macro2::TokenStream&lt;/code&gt; and not a &lt;code&gt;proc_macro::TokenStream&lt;/code&gt;, so drop a &lt;code&gt;.into()&lt;/code&gt; to convert it.&lt;/p&gt; 334&lt;p&gt;We haven’t filled in &lt;code&gt;generate_curry&lt;/code&gt; yet, but we can see that it returns a &lt;code&gt;proc_macro2::TokenStream&lt;/code&gt; and not a &lt;code&gt;proc_macro::TokenStream&lt;/code&gt;, so drop a &lt;code&gt;.into()&lt;/code&gt; to convert it.&lt;/p&gt;
303&lt;p&gt;Lets move on, and fill in &lt;code&gt;generate_curry&lt;/code&gt;, I would suggest keeping the documentation for &lt;a href="https://docs.rs/syn/1.0.19/syn/struct.ItemFn.html"&gt;&lt;code&gt;syn::ItemFn&lt;/code&gt;&lt;/a&gt; and &lt;a href="https://docs.rs/syn/1.0.19/syn/struct.Signature.html"&gt;&lt;code&gt;syn::Signature&lt;/code&gt;&lt;/a&gt; open.&lt;/p&gt; 335&lt;p&gt;Lets move on, and fill in &lt;code&gt;generate_curry&lt;/code&gt;, I would suggest keeping the documentation for &lt;a href="https://docs.rs/syn/1.0.19/syn/struct.ItemFn.html"&gt;&lt;code&gt;syn::ItemFn&lt;/code&gt;&lt;/a&gt; and &lt;a href="https://docs.rs/syn/1.0.19/syn/struct.Signature.html"&gt;&lt;code&gt;syn::Signature&lt;/code&gt;&lt;/a&gt; open.&lt;/p&gt;
304&lt;div class="sourceCode" id="cb14"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb14-1"&gt;&lt;a href="#cb14-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt; 336&lt;div class="sourceCode" id="cb14"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb14-1"&gt;&lt;a href="#cb14-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
305&lt;span id="cb14-2"&gt;&lt;a href="#cb14-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 337&lt;span id="cb14-2"&gt;&lt;a href="#cb14-2"&gt;&lt;/a&gt;&lt;/span&gt;
306&lt;span id="cb14-3"&gt;&lt;a href="#cb14-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; generate_curry(parsed&lt;span class="op"&gt;:&lt;/span&gt; ItemFn) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="pp"&gt;proc_macro2::&lt;/span&gt;TokenStream &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 338&lt;span id="cb14-3"&gt;&lt;a href="#cb14-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; generate_curry(parsed: ItemFn) -&amp;gt; &lt;span class="pp"&gt;proc_macro2::&lt;/span&gt;TokenStream &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
307&lt;span id="cb14-4"&gt;&lt;a href="#cb14-4" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_body &lt;span class="op"&gt;=&lt;/span&gt; parsed&lt;span class="op"&gt;.&lt;/span&gt;block&lt;span class="op"&gt;;&lt;/span&gt; &lt;span class="co"&gt;// function body&lt;/span&gt;&lt;/span&gt; 339&lt;span id="cb14-4"&gt;&lt;a href="#cb14-4"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_body = parsed.block; &lt;span class="co"&gt;// function body&lt;/span&gt;&lt;/span&gt;
308&lt;span id="cb14-5"&gt;&lt;a href="#cb14-5" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; sig &lt;span class="op"&gt;=&lt;/span&gt; parsed&lt;span class="op"&gt;.&lt;/span&gt;sig&lt;span class="op"&gt;;&lt;/span&gt; &lt;span class="co"&gt;// function signature&lt;/span&gt;&lt;/span&gt; 340&lt;span id="cb14-5"&gt;&lt;a href="#cb14-5"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; sig = parsed.sig; &lt;span class="co"&gt;// function signature&lt;/span&gt;&lt;/span&gt;
309&lt;span id="cb14-6"&gt;&lt;a href="#cb14-6" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; vis &lt;span class="op"&gt;=&lt;/span&gt; parsed&lt;span class="op"&gt;.&lt;/span&gt;vis&lt;span class="op"&gt;;&lt;/span&gt; &lt;span class="co"&gt;// visibility, pub or not&lt;/span&gt;&lt;/span&gt; 341&lt;span id="cb14-6"&gt;&lt;a href="#cb14-6"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; vis = parsed.vis; &lt;span class="co"&gt;// visibility, pub or not&lt;/span&gt;&lt;/span&gt;
310&lt;span id="cb14-7"&gt;&lt;a href="#cb14-7" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_name &lt;span class="op"&gt;=&lt;/span&gt; sig&lt;span class="op"&gt;.&lt;/span&gt;ident&lt;span class="op"&gt;;&lt;/span&gt; &lt;span class="co"&gt;// function name/identifier&lt;/span&gt;&lt;/span&gt; 342&lt;span id="cb14-7"&gt;&lt;a href="#cb14-7"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_name = sig.ident; &lt;span class="co"&gt;// function name/identifier&lt;/span&gt;&lt;/span&gt;
311&lt;span id="cb14-8"&gt;&lt;a href="#cb14-8" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_args &lt;span class="op"&gt;=&lt;/span&gt; sig&lt;span class="op"&gt;.&lt;/span&gt;inputs&lt;span class="op"&gt;;&lt;/span&gt; &lt;span class="co"&gt;// comma separated args&lt;/span&gt;&lt;/span&gt; 343&lt;span id="cb14-8"&gt;&lt;a href="#cb14-8"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_args = sig.inputs; &lt;span class="co"&gt;// comma separated args&lt;/span&gt;&lt;/span&gt;
312&lt;span id="cb14-9"&gt;&lt;a href="#cb14-9" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_return_type &lt;span class="op"&gt;=&lt;/span&gt; sig&lt;span class="op"&gt;.&lt;/span&gt;output&lt;span class="op"&gt;;&lt;/span&gt; &lt;span class="co"&gt;// return type&lt;/span&gt;&lt;/span&gt; 344&lt;span id="cb14-9"&gt;&lt;a href="#cb14-9"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_return_type = sig.output; &lt;span class="co"&gt;// return type&lt;/span&gt;&lt;/span&gt;
313&lt;span id="cb14-10"&gt;&lt;a href="#cb14-10" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 345&lt;span id="cb14-10"&gt;&lt;a href="#cb14-10"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
314&lt;p&gt;We are simply extracting the bits of the function, we will be reusing the original function’s visibility and name. Take a look at what &lt;code&gt;syn::Signature&lt;/code&gt; can tell us about a function:&lt;/p&gt; 346&lt;p&gt;We are simply extracting the bits of the function, we will be reusing the original function’s visibility and name. Take a look at what &lt;code&gt;syn::Signature&lt;/code&gt; can tell us about a function:&lt;/p&gt;
315&lt;pre&gt;&lt;code&gt; .-- syn::Ident (ident) 347&lt;pre&gt;&lt;code&gt; .-- syn::Ident (ident)
316 / 348 /
@@ -322,220 +354,220 @@ syn::token::Fn --&amp;#39; / \ (output)
322&lt;p&gt;Enough analysis, lets produce our first bit of Rust code.&lt;/p&gt; 354&lt;p&gt;Enough analysis, lets produce our first bit of Rust code.&lt;/p&gt;
323&lt;h4 id="function-body"&gt;Function Body&lt;/h4&gt; 355&lt;h4 id="function-body"&gt;Function Body&lt;/h4&gt;
324&lt;p&gt;Recall that the body of a curried &lt;code&gt;add&lt;/code&gt; should look like this:&lt;/p&gt; 356&lt;p&gt;Recall that the body of a curried &lt;code&gt;add&lt;/code&gt; should look like this:&lt;/p&gt;
325&lt;div class="sourceCode" id="cb16"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb16-1"&gt;&lt;a href="#cb16-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="kw"&gt;move&lt;/span&gt; &lt;span class="op"&gt;|&lt;/span&gt;y&lt;span class="op"&gt;|&lt;/span&gt; &lt;span class="kw"&gt;move&lt;/span&gt; &lt;span class="op"&gt;|&lt;/span&gt;z&lt;span class="op"&gt;|&lt;/span&gt; x &lt;span class="op"&gt;+&lt;/span&gt; y &lt;span class="op"&gt;+&lt;/span&gt; z&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 357&lt;div class="sourceCode" id="cb16"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb16-1"&gt;&lt;a href="#cb16-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="kw"&gt;move&lt;/span&gt; |y| &lt;span class="kw"&gt;move&lt;/span&gt; |z| x + y + z;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
326&lt;p&gt;And in general:&lt;/p&gt; 358&lt;p&gt;And in general:&lt;/p&gt;
327&lt;div class="sourceCode" id="cb17"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb17-1"&gt;&lt;a href="#cb17-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="kw"&gt;move&lt;/span&gt; &lt;span class="op"&gt;|&lt;/span&gt;arg2&lt;span class="op"&gt;|&lt;/span&gt; &lt;span class="kw"&gt;move&lt;/span&gt; &lt;span class="op"&gt;|&lt;/span&gt;arg3&lt;span class="op"&gt;|&lt;/span&gt; &lt;span class="op"&gt;...&lt;/span&gt; &lt;span class="op"&gt;|&lt;/span&gt;argN&lt;span class="op"&gt;|&lt;/span&gt; &lt;span class="op"&gt;&amp;lt;&lt;/span&gt;function body here&lt;span class="op"&gt;&amp;gt;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 359&lt;div class="sourceCode" id="cb17"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb17-1"&gt;&lt;a href="#cb17-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="kw"&gt;move&lt;/span&gt; |arg2| &lt;span class="kw"&gt;move&lt;/span&gt; |arg3| ... |argN| &amp;lt;function body here&amp;gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
328&lt;p&gt;We already have the function’s body, provided by &lt;code&gt;fn_body&lt;/code&gt;, in our &lt;code&gt;generate_curry&lt;/code&gt; function. All that’s left to add is the &lt;code&gt;move |arg2| move |arg3| ...&lt;/code&gt; stuff, for which we need to extract the argument identifiers (doc: &lt;a href="https://docs.rs/syn/1.0.18/syn/punctuated/struct.Punctuated.html"&gt;Punctuated&lt;/a&gt;, &lt;a href="https://docs.rs/syn/1.0.18/syn/enum.FnArg.html"&gt;FnArg&lt;/a&gt;, &lt;a href="https://docs.rs/syn/1.0.18/syn/struct.PatType.html"&gt;PatType&lt;/a&gt;):&lt;/p&gt; 360&lt;p&gt;We already have the function’s body, provided by &lt;code&gt;fn_body&lt;/code&gt;, in our &lt;code&gt;generate_curry&lt;/code&gt; function. All that’s left to add is the &lt;code&gt;move |arg2| move |arg3| ...&lt;/code&gt; stuff, for which we need to extract the argument identifiers (doc: &lt;a href="https://docs.rs/syn/1.0.18/syn/punctuated/struct.Punctuated.html"&gt;Punctuated&lt;/a&gt;, &lt;a href="https://docs.rs/syn/1.0.18/syn/enum.FnArg.html"&gt;FnArg&lt;/a&gt;, &lt;a href="https://docs.rs/syn/1.0.18/syn/struct.PatType.html"&gt;PatType&lt;/a&gt;):&lt;/p&gt;
329&lt;div class="sourceCode" id="cb18"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb18-1"&gt;&lt;a href="#cb18-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt; 361&lt;div class="sourceCode" id="cb18"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb18-1"&gt;&lt;a href="#cb18-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
330&lt;span id="cb18-2"&gt;&lt;a href="#cb18-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;syn::punctuated::&lt;/span&gt;Punctuated&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 362&lt;span id="cb18-2"&gt;&lt;a href="#cb18-2"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;syn::punctuated::&lt;/span&gt;Punctuated;&lt;/span&gt;
331&lt;span id="cb18-3"&gt;&lt;a href="#cb18-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;syn::&lt;/span&gt;&lt;span class="op"&gt;{&lt;/span&gt;parse_macro_input&lt;span class="op"&gt;,&lt;/span&gt; FnArg&lt;span class="op"&gt;,&lt;/span&gt; Pat&lt;span class="op"&gt;,&lt;/span&gt; ItemFn&lt;span class="op"&gt;,&lt;/span&gt; Block&lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt; 363&lt;span id="cb18-3"&gt;&lt;a href="#cb18-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;syn::&lt;/span&gt;&lt;span class="op"&gt;{&lt;/span&gt;parse_macro_input, FnArg, Pat, ItemFn, Block&lt;span class="op"&gt;}&lt;/span&gt;;&lt;/span&gt;
332&lt;span id="cb18-4"&gt;&lt;a href="#cb18-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 364&lt;span id="cb18-4"&gt;&lt;a href="#cb18-4"&gt;&lt;/a&gt;&lt;/span&gt;
333&lt;span id="cb18-5"&gt;&lt;a href="#cb18-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; extract_arg_idents(fn_args&lt;span class="op"&gt;:&lt;/span&gt; Punctuated&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;FnArg&lt;span class="op"&gt;,&lt;/span&gt; &lt;span class="pp"&gt;syn::token::&lt;/span&gt;Comma&lt;span class="op"&gt;&amp;gt;&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;Vec&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;&lt;span class="dt"&gt;Box&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;Pat&lt;span class="op"&gt;&amp;gt;&amp;gt;&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt; &lt;/span&gt; 365&lt;span id="cb18-5"&gt;&lt;a href="#cb18-5"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; extract_arg_idents(fn_args: Punctuated&amp;lt;FnArg, &lt;span class="pp"&gt;syn::token::&lt;/span&gt;Comma&amp;gt;) -&amp;gt; &lt;span class="dt"&gt;Vec&lt;/span&gt;&amp;lt;&lt;span class="dt"&gt;Box&lt;/span&gt;&amp;lt;Pat&amp;gt;&amp;gt; &lt;span class="op"&gt;{&lt;/span&gt; &lt;/span&gt;
334&lt;span id="cb18-6"&gt;&lt;a href="#cb18-6" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; fn_args&lt;span class="op"&gt;.&lt;/span&gt;into_iter()&lt;span class="op"&gt;.&lt;/span&gt;map(extract_arg_pat)&lt;span class="op"&gt;.&lt;/span&gt;&lt;span class="pp"&gt;collect::&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;&lt;span class="dt"&gt;Vec&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;_&lt;span class="op"&gt;&amp;gt;&amp;gt;&lt;/span&gt;()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 366&lt;span id="cb18-6"&gt;&lt;a href="#cb18-6"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; fn_args.into_iter().map(extract_arg_pat).&lt;span class="pp"&gt;collect::&lt;/span&gt;&amp;lt;&lt;span class="dt"&gt;Vec&lt;/span&gt;&amp;lt;_&amp;gt;&amp;gt;();&lt;/span&gt;
335&lt;span id="cb18-7"&gt;&lt;a href="#cb18-7" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 367&lt;span id="cb18-7"&gt;&lt;a href="#cb18-7"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
336&lt;p&gt;Alright, so we are iterating over function args (&lt;code&gt;Punctuated&lt;/code&gt; is a collection that you can iterate over) and mapping an &lt;code&gt;extract_arg_pat&lt;/code&gt; to every item. What’s &lt;code&gt;extract_arg_pat&lt;/code&gt;?&lt;/p&gt; 368&lt;p&gt;Alright, so we are iterating over function args (&lt;code&gt;Punctuated&lt;/code&gt; is a collection that you can iterate over) and mapping an &lt;code&gt;extract_arg_pat&lt;/code&gt; to every item. What’s &lt;code&gt;extract_arg_pat&lt;/code&gt;?&lt;/p&gt;
337&lt;div class="sourceCode" id="cb19"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb19-1"&gt;&lt;a href="#cb19-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt; 369&lt;div class="sourceCode" id="cb19"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb19-1"&gt;&lt;a href="#cb19-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
338&lt;span id="cb19-2"&gt;&lt;a href="#cb19-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 370&lt;span id="cb19-2"&gt;&lt;a href="#cb19-2"&gt;&lt;/a&gt;&lt;/span&gt;
339&lt;span id="cb19-3"&gt;&lt;a href="#cb19-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; extract_arg_pat(a&lt;span class="op"&gt;:&lt;/span&gt; FnArg) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;Box&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;Pat&lt;span class="op"&gt;&amp;gt;&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 371&lt;span id="cb19-3"&gt;&lt;a href="#cb19-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; extract_arg_pat(a: FnArg) -&amp;gt; &lt;span class="dt"&gt;Box&lt;/span&gt;&amp;lt;Pat&amp;gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
340&lt;span id="cb19-4"&gt;&lt;a href="#cb19-4" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;match&lt;/span&gt; a &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 372&lt;span id="cb19-4"&gt;&lt;a href="#cb19-4"&gt;&lt;/a&gt; &lt;span class="kw"&gt;match&lt;/span&gt; a &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
341&lt;span id="cb19-5"&gt;&lt;a href="#cb19-5" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="pp"&gt;FnArg::&lt;/span&gt;Typed(p) &lt;span class="op"&gt;=&amp;gt;&lt;/span&gt; p&lt;span class="op"&gt;.&lt;/span&gt;pat&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt; 373&lt;span id="cb19-5"&gt;&lt;a href="#cb19-5"&gt;&lt;/a&gt; &lt;span class="pp"&gt;FnArg::&lt;/span&gt;Typed(p) =&amp;gt; p.pat,&lt;/span&gt;
342&lt;span id="cb19-6"&gt;&lt;a href="#cb19-6" aria-hidden="true"&gt;&lt;/a&gt; _ &lt;span class="op"&gt;=&amp;gt;&lt;/span&gt; &lt;span class="pp"&gt;panic!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;Not supported on types with `self`!&amp;quot;&lt;/span&gt;)&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt; 374&lt;span id="cb19-6"&gt;&lt;a href="#cb19-6"&gt;&lt;/a&gt; _ =&amp;gt; &lt;span class="pp"&gt;panic!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;Not supported on types with `self`!&amp;quot;&lt;/span&gt;),&lt;/span&gt;
343&lt;span id="cb19-7"&gt;&lt;a href="#cb19-7" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 375&lt;span id="cb19-7"&gt;&lt;a href="#cb19-7"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
344&lt;span id="cb19-8"&gt;&lt;a href="#cb19-8" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 376&lt;span id="cb19-8"&gt;&lt;a href="#cb19-8"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
345&lt;p&gt;&lt;code&gt;FnArg&lt;/code&gt; is an enum type as you might have guessed. The &lt;code&gt;Typed&lt;/code&gt; variant encompasses args that are written as &lt;code&gt;name: type&lt;/code&gt; and the other variant, &lt;code&gt;Reciever&lt;/code&gt; refers to &lt;code&gt;self&lt;/code&gt; types. Ignore those for now, keep it simple.&lt;/p&gt; 377&lt;p&gt;&lt;code&gt;FnArg&lt;/code&gt; is an enum type as you might have guessed. The &lt;code&gt;Typed&lt;/code&gt; variant encompasses args that are written as &lt;code&gt;name: type&lt;/code&gt; and the other variant, &lt;code&gt;Reciever&lt;/code&gt; refers to &lt;code&gt;self&lt;/code&gt; types. Ignore those for now, keep it simple.&lt;/p&gt;
346&lt;p&gt;Every &lt;code&gt;FnArg::Typed&lt;/code&gt; value contains a &lt;code&gt;pat&lt;/code&gt;, which is in essence, the name of the argument. The type of the arg is accessible via &lt;code&gt;p.ty&lt;/code&gt; (we will be using this later).&lt;/p&gt; 378&lt;p&gt;Every &lt;code&gt;FnArg::Typed&lt;/code&gt; value contains a &lt;code&gt;pat&lt;/code&gt;, which is in essence, the name of the argument. The type of the arg is accessible via &lt;code&gt;p.ty&lt;/code&gt; (we will be using this later).&lt;/p&gt;
347&lt;p&gt;With that done, we should be able to write the codegen for the function body:&lt;/p&gt; 379&lt;p&gt;With that done, we should be able to write the codegen for the function body:&lt;/p&gt;
348&lt;div class="sourceCode" id="cb20"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb20-1"&gt;&lt;a href="#cb20-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt; 380&lt;div class="sourceCode" id="cb20"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb20-1"&gt;&lt;a href="#cb20-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
349&lt;span id="cb20-2"&gt;&lt;a href="#cb20-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 381&lt;span id="cb20-2"&gt;&lt;a href="#cb20-2"&gt;&lt;/a&gt;&lt;/span&gt;
350&lt;span id="cb20-3"&gt;&lt;a href="#cb20-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; generate_body(fn_args&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="op"&gt;&amp;amp;&lt;/span&gt;[&lt;span class="dt"&gt;Box&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;Pat&lt;span class="op"&gt;&amp;gt;&lt;/span&gt;]&lt;span class="op"&gt;,&lt;/span&gt; body&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;Box&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;Block&lt;span class="op"&gt;&amp;gt;&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="pp"&gt;proc_macro2::&lt;/span&gt;TokenStream &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 382&lt;span id="cb20-3"&gt;&lt;a href="#cb20-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; generate_body(fn_args: &amp;amp;&lt;span class="op"&gt;[&lt;/span&gt;&lt;span class="dt"&gt;Box&lt;/span&gt;&amp;lt;Pat&amp;gt;&lt;span class="op"&gt;]&lt;/span&gt;, body: &lt;span class="dt"&gt;Box&lt;/span&gt;&amp;lt;Block&amp;gt;) -&amp;gt; &lt;span class="pp"&gt;proc_macro2::&lt;/span&gt;TokenStream &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
351&lt;span id="cb20-4"&gt;&lt;a href="#cb20-4" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="pp"&gt;quote!&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 383&lt;span id="cb20-4"&gt;&lt;a href="#cb20-4"&gt;&lt;/a&gt; &lt;span class="pp"&gt;quote!&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
352&lt;span id="cb20-5"&gt;&lt;a href="#cb20-5" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; #( &lt;span class="kw"&gt;move&lt;/span&gt; &lt;span class="op"&gt;|&lt;/span&gt;#fn_args&lt;span class="op"&gt;|&lt;/span&gt; )&lt;span class="op"&gt;*&lt;/span&gt; #body&lt;/span&gt; 384&lt;span id="cb20-5"&gt;&lt;a href="#cb20-5"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; #( &lt;span class="kw"&gt;move&lt;/span&gt; |#fn_args| )* #body&lt;/span&gt;
353&lt;span id="cb20-6"&gt;&lt;a href="#cb20-6" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 385&lt;span id="cb20-6"&gt;&lt;a href="#cb20-6"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
354&lt;span id="cb20-7"&gt;&lt;a href="#cb20-7" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 386&lt;span id="cb20-7"&gt;&lt;a href="#cb20-7"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
355&lt;p&gt;That is some scary looking syntax! Allow me to explain. The &lt;code&gt;quote!{ ... }&lt;/code&gt; returns a &lt;code&gt;proc_macro2::TokenStream&lt;/code&gt;, if we wrote &lt;code&gt;quote!{ let x = 1 + 2; }&lt;/code&gt;, it wouldn’t create a new variable &lt;code&gt;x&lt;/code&gt; with value 3, it would literally produce a stream of tokens with that expression.&lt;/p&gt; 387&lt;p&gt;That is some scary looking syntax! Allow me to explain. The &lt;code&gt;quote!{ ... }&lt;/code&gt; returns a &lt;code&gt;proc_macro2::TokenStream&lt;/code&gt;, if we wrote &lt;code&gt;quote!{ let x = 1 + 2; }&lt;/code&gt;, it wouldn’t create a new variable &lt;code&gt;x&lt;/code&gt; with value 3, it would literally produce a stream of tokens with that expression.&lt;/p&gt;
356&lt;p&gt;The &lt;code&gt;#&lt;/code&gt; enables variable interpolation. &lt;code&gt;#body&lt;/code&gt; will look for &lt;code&gt;body&lt;/code&gt; in the current scope, take its value, and insert it in the returned &lt;code&gt;TokenStream&lt;/code&gt;. Kinda like quasi quoting in LISPs, you have written one.&lt;/p&gt; 388&lt;p&gt;The &lt;code&gt;#&lt;/code&gt; enables variable interpolation. &lt;code&gt;#body&lt;/code&gt; will look for &lt;code&gt;body&lt;/code&gt; in the current scope, take its value, and insert it in the returned &lt;code&gt;TokenStream&lt;/code&gt;. Kinda like quasi quoting in LISPs, you have written one.&lt;/p&gt;
357&lt;p&gt;What about &lt;code&gt;#( move |#fn_args| )*&lt;/code&gt;? That is repetition. &lt;code&gt;quote&lt;/code&gt; iterates through &lt;code&gt;fn_args&lt;/code&gt;, and drops a &lt;code&gt;move&lt;/code&gt; behind each one, it then places pipes (&lt;code&gt;|&lt;/code&gt;), around it.&lt;/p&gt; 389&lt;p&gt;What about &lt;code&gt;#( move |#fn_args| )*&lt;/code&gt;? That is repetition. &lt;code&gt;quote&lt;/code&gt; iterates through &lt;code&gt;fn_args&lt;/code&gt;, and drops a &lt;code&gt;move&lt;/code&gt; behind each one, it then places pipes (&lt;code&gt;|&lt;/code&gt;), around it.&lt;/p&gt;
358&lt;p&gt;Let us test our first bit of codegen! Modify &lt;code&gt;generate_curry&lt;/code&gt; like so:&lt;/p&gt; 390&lt;p&gt;Let us test our first bit of codegen! Modify &lt;code&gt;generate_curry&lt;/code&gt; like so:&lt;/p&gt;
359&lt;div class="sourceCode" id="cb21"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb21-1"&gt;&lt;a href="#cb21-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt; 391&lt;div class="sourceCode" id="cb21"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb21-1"&gt;&lt;a href="#cb21-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
360&lt;span id="cb21-2"&gt;&lt;a href="#cb21-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 392&lt;span id="cb21-2"&gt;&lt;a href="#cb21-2"&gt;&lt;/a&gt;&lt;/span&gt;
361&lt;span id="cb21-3"&gt;&lt;a href="#cb21-3" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;fn&lt;/span&gt; generate_curry(parsed&lt;span class="op"&gt;:&lt;/span&gt; ItemFn) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; TokenStream &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 393&lt;span id="cb21-3"&gt;&lt;a href="#cb21-3"&gt;&lt;/a&gt; &lt;span class="kw"&gt;fn&lt;/span&gt; generate_curry(parsed: ItemFn) -&amp;gt; TokenStream &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
362&lt;span id="cb21-4"&gt;&lt;a href="#cb21-4" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_body &lt;span class="op"&gt;=&lt;/span&gt; parsed&lt;span class="op"&gt;.&lt;/span&gt;block&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 394&lt;span id="cb21-4"&gt;&lt;a href="#cb21-4"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_body = parsed.block;&lt;/span&gt;
363&lt;span id="cb21-5"&gt;&lt;a href="#cb21-5" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; sig &lt;span class="op"&gt;=&lt;/span&gt; parsed&lt;span class="op"&gt;.&lt;/span&gt;sig&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 395&lt;span id="cb21-5"&gt;&lt;a href="#cb21-5"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; sig = parsed.sig;&lt;/span&gt;
364&lt;span id="cb21-6"&gt;&lt;a href="#cb21-6" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; vis &lt;span class="op"&gt;=&lt;/span&gt; parsed&lt;span class="op"&gt;.&lt;/span&gt;vis&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 396&lt;span id="cb21-6"&gt;&lt;a href="#cb21-6"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; vis = parsed.vis;&lt;/span&gt;
365&lt;span id="cb21-7"&gt;&lt;a href="#cb21-7" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_name &lt;span class="op"&gt;=&lt;/span&gt; sig&lt;span class="op"&gt;.&lt;/span&gt;ident&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 397&lt;span id="cb21-7"&gt;&lt;a href="#cb21-7"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_name = sig.ident;&lt;/span&gt;
366&lt;span id="cb21-8"&gt;&lt;a href="#cb21-8" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_args &lt;span class="op"&gt;=&lt;/span&gt; sig&lt;span class="op"&gt;.&lt;/span&gt;inputs&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 398&lt;span id="cb21-8"&gt;&lt;a href="#cb21-8"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_args = sig.inputs;&lt;/span&gt;
367&lt;span id="cb21-9"&gt;&lt;a href="#cb21-9" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_return_type &lt;span class="op"&gt;=&lt;/span&gt; sig&lt;span class="op"&gt;.&lt;/span&gt;output&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 399&lt;span id="cb21-9"&gt;&lt;a href="#cb21-9"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_return_type = sig.output;&lt;/span&gt;
368&lt;span id="cb21-10"&gt;&lt;a href="#cb21-10" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 400&lt;span id="cb21-10"&gt;&lt;a href="#cb21-10"&gt;&lt;/a&gt;&lt;/span&gt;
369&lt;span id="cb21-11"&gt;&lt;a href="#cb21-11" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="kw"&gt;let&lt;/span&gt; arg_idents &lt;span class="op"&gt;=&lt;/span&gt; extract_arg_idents(fn_args&lt;span class="op"&gt;.&lt;/span&gt;clone())&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 401&lt;span id="cb21-11"&gt;&lt;a href="#cb21-11"&gt;&lt;/a&gt;+ &lt;span class="kw"&gt;let&lt;/span&gt; arg_idents = extract_arg_idents(fn_args.clone());&lt;/span&gt;
370&lt;span id="cb21-12"&gt;&lt;a href="#cb21-12" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="kw"&gt;let&lt;/span&gt; first_ident &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;&amp;amp;&lt;/span&gt;arg_idents&lt;span class="op"&gt;.&lt;/span&gt;first()&lt;span class="op"&gt;.&lt;/span&gt;unwrap()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 402&lt;span id="cb21-12"&gt;&lt;a href="#cb21-12"&gt;&lt;/a&gt;+ &lt;span class="kw"&gt;let&lt;/span&gt; first_ident = &amp;amp;arg_idents.first().unwrap();&lt;/span&gt;
371&lt;span id="cb21-13"&gt;&lt;a href="#cb21-13" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 403&lt;span id="cb21-13"&gt;&lt;a href="#cb21-13"&gt;&lt;/a&gt;&lt;/span&gt;
372&lt;span id="cb21-14"&gt;&lt;a href="#cb21-14" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="co"&gt;// remember, our curried body starts with the second argument!&lt;/span&gt;&lt;/span&gt; 404&lt;span id="cb21-14"&gt;&lt;a href="#cb21-14"&gt;&lt;/a&gt;+ &lt;span class="co"&gt;// remember, our curried body starts with the second argument!&lt;/span&gt;&lt;/span&gt;
373&lt;span id="cb21-15"&gt;&lt;a href="#cb21-15" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="kw"&gt;let&lt;/span&gt; curried_body &lt;span class="op"&gt;=&lt;/span&gt; generate_body(&lt;span class="op"&gt;&amp;amp;&lt;/span&gt;arg_idents[&lt;span class="dv"&gt;1&lt;/span&gt;&lt;span class="op"&gt;..&lt;/span&gt;]&lt;span class="op"&gt;,&lt;/span&gt; fn_body&lt;span class="op"&gt;.&lt;/span&gt;clone())&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 405&lt;span id="cb21-15"&gt;&lt;a href="#cb21-15"&gt;&lt;/a&gt;+ &lt;span class="kw"&gt;let&lt;/span&gt; curried_body = generate_body(&amp;amp;arg_idents&lt;span class="op"&gt;[&lt;/span&gt;&lt;span class="dv"&gt;1&lt;/span&gt;..&lt;span class="op"&gt;]&lt;/span&gt;, fn_body.clone());&lt;/span&gt;
374&lt;span id="cb21-16"&gt;&lt;a href="#cb21-16" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="pp"&gt;println!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;{}&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; curried_body)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 406&lt;span id="cb21-16"&gt;&lt;a href="#cb21-16"&gt;&lt;/a&gt;+ &lt;span class="pp"&gt;println!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;{}&amp;quot;&lt;/span&gt;, curried_body);&lt;/span&gt;
375&lt;span id="cb21-17"&gt;&lt;a href="#cb21-17" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 407&lt;span id="cb21-17"&gt;&lt;a href="#cb21-17"&gt;&lt;/a&gt;&lt;/span&gt;
376&lt;span id="cb21-18"&gt;&lt;a href="#cb21-18" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="pp"&gt;TokenStream::&lt;/span&gt;new()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 408&lt;span id="cb21-18"&gt;&lt;a href="#cb21-18"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="pp"&gt;TokenStream::&lt;/span&gt;new();&lt;/span&gt;
377&lt;span id="cb21-19"&gt;&lt;a href="#cb21-19" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 409&lt;span id="cb21-19"&gt;&lt;a href="#cb21-19"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
378&lt;p&gt;Add a little test to &lt;code&gt;tests/&lt;/code&gt;:&lt;/p&gt; 410&lt;p&gt;Add a little test to &lt;code&gt;tests/&lt;/code&gt;:&lt;/p&gt;
379&lt;div class="sourceCode" id="cb22"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb22-1"&gt;&lt;a href="#cb22-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// tests/smoke.rs&lt;/span&gt;&lt;/span&gt; 411&lt;div class="sourceCode" id="cb22"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb22-1"&gt;&lt;a href="#cb22-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// tests/smoke.rs&lt;/span&gt;&lt;/span&gt;
380&lt;span id="cb22-2"&gt;&lt;a href="#cb22-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 412&lt;span id="cb22-2"&gt;&lt;a href="#cb22-2"&gt;&lt;/a&gt;&lt;/span&gt;
381&lt;span id="cb22-3"&gt;&lt;a href="#cb22-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;&lt;span class="pp"&gt;currying::&lt;/span&gt;curry&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt; 413&lt;span id="cb22-3"&gt;&lt;a href="#cb22-3"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;&lt;span class="pp"&gt;currying::&lt;/span&gt;curry&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt;
382&lt;span id="cb22-4"&gt;&lt;a href="#cb22-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add(x&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; y&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; z&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 414&lt;span id="cb22-4"&gt;&lt;a href="#cb22-4"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add(x: &lt;span class="dt"&gt;u32&lt;/span&gt;, y: &lt;span class="dt"&gt;u32&lt;/span&gt;, z: &lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
383&lt;span id="cb22-5"&gt;&lt;a href="#cb22-5" aria-hidden="true"&gt;&lt;/a&gt; x &lt;span class="op"&gt;+&lt;/span&gt; y &lt;span class="op"&gt;+&lt;/span&gt; z&lt;/span&gt; 415&lt;span id="cb22-5"&gt;&lt;a href="#cb22-5"&gt;&lt;/a&gt; x + y + z&lt;/span&gt;
384&lt;span id="cb22-6"&gt;&lt;a href="#cb22-6" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 416&lt;span id="cb22-6"&gt;&lt;a href="#cb22-6"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
385&lt;span id="cb22-7"&gt;&lt;a href="#cb22-7" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 417&lt;span id="cb22-7"&gt;&lt;a href="#cb22-7"&gt;&lt;/a&gt;&lt;/span&gt;
386&lt;span id="cb22-8"&gt;&lt;a href="#cb22-8" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;test&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt; 418&lt;span id="cb22-8"&gt;&lt;a href="#cb22-8"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;test&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt;
387&lt;span id="cb22-9"&gt;&lt;a href="#cb22-9" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; works() &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 419&lt;span id="cb22-9"&gt;&lt;a href="#cb22-9"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; works() &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
388&lt;span id="cb22-10"&gt;&lt;a href="#cb22-10" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="pp"&gt;assert!&lt;/span&gt;(&lt;span class="cn"&gt;true&lt;/span&gt;)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 420&lt;span id="cb22-10"&gt;&lt;a href="#cb22-10"&gt;&lt;/a&gt; &lt;span class="pp"&gt;assert!&lt;/span&gt;(&lt;span class="cn"&gt;true&lt;/span&gt;);&lt;/span&gt;
389&lt;span id="cb22-11"&gt;&lt;a href="#cb22-11" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 421&lt;span id="cb22-11"&gt;&lt;a href="#cb22-11"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
390&lt;p&gt;You should find something like this in the output of &lt;code&gt;cargo test&lt;/code&gt;:&lt;/p&gt; 422&lt;p&gt;You should find something like this in the output of &lt;code&gt;cargo test&lt;/code&gt;:&lt;/p&gt;
391&lt;pre&gt;&lt;code&gt;return move | y | move | z | { x + y + z }&lt;/code&gt;&lt;/pre&gt; 423&lt;pre&gt;&lt;code&gt;return move | y | move | z | { x + y + z }&lt;/code&gt;&lt;/pre&gt;
392&lt;p&gt;Glorious &lt;code&gt;println!&lt;/code&gt; debugging!&lt;/p&gt; 424&lt;p&gt;Glorious &lt;code&gt;println!&lt;/code&gt; debugging!&lt;/p&gt;
393&lt;h4 id="function-signature"&gt;Function signature&lt;/h4&gt; 425&lt;h4 id="function-signature"&gt;Function signature&lt;/h4&gt;
394&lt;p&gt;This section gets into the more complicated bits of the macro, generating type aliases and the function signature. By the end of this section, we should have a full working auto-currying macro!&lt;/p&gt; 426&lt;p&gt;This section gets into the more complicated bits of the macro, generating type aliases and the function signature. By the end of this section, we should have a full working auto-currying macro!&lt;/p&gt;
395&lt;p&gt;Recall what our generated type aliases should look like, for our &lt;code&gt;add&lt;/code&gt; function:&lt;/p&gt; 427&lt;p&gt;Recall what our generated type aliases should look like, for our &lt;code&gt;add&lt;/code&gt; function:&lt;/p&gt;
396&lt;div class="sourceCode" id="cb24"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb24-1"&gt;&lt;a href="#cb24-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 428&lt;div class="sourceCode" id="cb24"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb24-1"&gt;&lt;a href="#cb24-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 = &lt;span class="dt"&gt;u32&lt;/span&gt;;&lt;/span&gt;
397&lt;span id="cb24-2"&gt;&lt;a href="#cb24-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T1 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; T0&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 429&lt;span id="cb24-2"&gt;&lt;a href="#cb24-2"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T1 = &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; T0;&lt;/span&gt;
398&lt;span id="cb24-3"&gt;&lt;a href="#cb24-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T2 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; T1&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 430&lt;span id="cb24-3"&gt;&lt;a href="#cb24-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T2 = &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; T1;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
399&lt;p&gt;In general:&lt;/p&gt; 431&lt;p&gt;In general:&lt;/p&gt;
400&lt;div class="sourceCode" id="cb25"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb25-1"&gt;&lt;a href="#cb25-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;&amp;lt;&lt;/span&gt;&lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="kw"&gt;type&lt;/span&gt;&amp;gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 432&lt;div class="sourceCode" id="cb25"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb25-1"&gt;&lt;a href="#cb25-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 = &amp;lt;&lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="kw"&gt;type&lt;/span&gt;&amp;gt;;&lt;/span&gt;
401&lt;span id="cb25-2"&gt;&lt;a href="#cb25-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T1 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;&lt;span class="kw"&gt;type&lt;/span&gt; of arg N&amp;gt;) -&amp;gt; T0&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 433&lt;span id="cb25-2"&gt;&lt;a href="#cb25-2"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T1 = &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&amp;lt;&lt;span class="kw"&gt;type&lt;/span&gt; of arg N&amp;gt;) -&amp;gt; T0;&lt;/span&gt;
402&lt;span id="cb25-3"&gt;&lt;a href="#cb25-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T2 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;&lt;span class="kw"&gt;type&lt;/span&gt; of arg N - 1&amp;gt;) -&amp;gt; T1&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 434&lt;span id="cb25-3"&gt;&lt;a href="#cb25-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T2 = &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&amp;lt;&lt;span class="kw"&gt;type&lt;/span&gt; of arg N - 1&amp;gt;) -&amp;gt; T1;&lt;/span&gt;
403&lt;span id="cb25-4"&gt;&lt;a href="#cb25-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;.&lt;/span&gt;&lt;/span&gt; 435&lt;span id="cb25-4"&gt;&lt;a href="#cb25-4"&gt;&lt;/a&gt;.&lt;/span&gt;
404&lt;span id="cb25-5"&gt;&lt;a href="#cb25-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;.&lt;/span&gt;&lt;/span&gt; 436&lt;span id="cb25-5"&gt;&lt;a href="#cb25-5"&gt;&lt;/a&gt;.&lt;/span&gt;
405&lt;span id="cb25-6"&gt;&lt;a href="#cb25-6" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;.&lt;/span&gt;&lt;/span&gt; 437&lt;span id="cb25-6"&gt;&lt;a href="#cb25-6"&gt;&lt;/a&gt;.&lt;/span&gt;
406&lt;span id="cb25-7"&gt;&lt;a href="#cb25-7" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T(N-1) &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;&lt;span class="kw"&gt;type&lt;/span&gt; of arg 2&amp;gt;) -&amp;gt; T(N-2)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 438&lt;span id="cb25-7"&gt;&lt;a href="#cb25-7"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T(N-1) = &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&amp;lt;&lt;span class="kw"&gt;type&lt;/span&gt; of arg 2&amp;gt;) -&amp;gt; T(N-2);&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
407&lt;p&gt;To codegen that, we need the types of:&lt;/p&gt; 439&lt;p&gt;To codegen that, we need the types of:&lt;/p&gt;
408&lt;ul&gt; 440&lt;ul&gt;
409&lt;li&gt;all our inputs (arguments)&lt;/li&gt; 441&lt;li&gt;all our inputs (arguments)&lt;/li&gt;
410&lt;li&gt;the output (the return type)&lt;/li&gt; 442&lt;li&gt;the output (the return type)&lt;/li&gt;
411&lt;/ul&gt; 443&lt;/ul&gt;
412&lt;p&gt;To fetch the types of all our inputs, we can simply reuse the bits we wrote to fetch the names of all our inputs! (doc: &lt;a href="https://docs.rs/syn/1.0.18/syn/enum.Type.html"&gt;Type&lt;/a&gt;)&lt;/p&gt; 444&lt;p&gt;To fetch the types of all our inputs, we can simply reuse the bits we wrote to fetch the names of all our inputs! (doc: &lt;a href="https://docs.rs/syn/1.0.18/syn/enum.Type.html"&gt;Type&lt;/a&gt;)&lt;/p&gt;
413&lt;div class="sourceCode" id="cb26"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb26-1"&gt;&lt;a href="#cb26-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt; 445&lt;div class="sourceCode" id="cb26"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb26-1"&gt;&lt;a href="#cb26-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
414&lt;span id="cb26-2"&gt;&lt;a href="#cb26-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 446&lt;span id="cb26-2"&gt;&lt;a href="#cb26-2"&gt;&lt;/a&gt;&lt;/span&gt;
415&lt;span id="cb26-3"&gt;&lt;a href="#cb26-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;syn::&lt;/span&gt;&lt;span class="op"&gt;{&lt;/span&gt;parse_macro_input&lt;span class="op"&gt;,&lt;/span&gt; Block&lt;span class="op"&gt;,&lt;/span&gt; FnArg&lt;span class="op"&gt;,&lt;/span&gt; ItemFn&lt;span class="op"&gt;,&lt;/span&gt; Pat&lt;span class="op"&gt;,&lt;/span&gt; ReturnType&lt;span class="op"&gt;,&lt;/span&gt; Type&lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt; 447&lt;span id="cb26-3"&gt;&lt;a href="#cb26-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;syn::&lt;/span&gt;&lt;span class="op"&gt;{&lt;/span&gt;parse_macro_input, Block, FnArg, ItemFn, Pat, ReturnType, Type&lt;span class="op"&gt;}&lt;/span&gt;;&lt;/span&gt;
416&lt;span id="cb26-4"&gt;&lt;a href="#cb26-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 448&lt;span id="cb26-4"&gt;&lt;a href="#cb26-4"&gt;&lt;/a&gt;&lt;/span&gt;
417&lt;span id="cb26-5"&gt;&lt;a href="#cb26-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; extract_type(a&lt;span class="op"&gt;:&lt;/span&gt; FnArg) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;Box&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;Type&lt;span class="op"&gt;&amp;gt;&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 449&lt;span id="cb26-5"&gt;&lt;a href="#cb26-5"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; extract_type(a: FnArg) -&amp;gt; &lt;span class="dt"&gt;Box&lt;/span&gt;&amp;lt;Type&amp;gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
418&lt;span id="cb26-6"&gt;&lt;a href="#cb26-6" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;match&lt;/span&gt; a &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 450&lt;span id="cb26-6"&gt;&lt;a href="#cb26-6"&gt;&lt;/a&gt; &lt;span class="kw"&gt;match&lt;/span&gt; a &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
419&lt;span id="cb26-7"&gt;&lt;a href="#cb26-7" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="pp"&gt;FnArg::&lt;/span&gt;Typed(p) &lt;span class="op"&gt;=&amp;gt;&lt;/span&gt; p&lt;span class="op"&gt;.&lt;/span&gt;ty&lt;span class="op"&gt;,&lt;/span&gt; &lt;span class="co"&gt;// notice `ty` instead of `pat`&lt;/span&gt;&lt;/span&gt; 451&lt;span id="cb26-7"&gt;&lt;a href="#cb26-7"&gt;&lt;/a&gt; &lt;span class="pp"&gt;FnArg::&lt;/span&gt;Typed(p) =&amp;gt; p.ty, &lt;span class="co"&gt;// notice `ty` instead of `pat`&lt;/span&gt;&lt;/span&gt;
420&lt;span id="cb26-8"&gt;&lt;a href="#cb26-8" aria-hidden="true"&gt;&lt;/a&gt; _ &lt;span class="op"&gt;=&amp;gt;&lt;/span&gt; &lt;span class="pp"&gt;panic!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;Not supported on types with `self`!&amp;quot;&lt;/span&gt;)&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt; 452&lt;span id="cb26-8"&gt;&lt;a href="#cb26-8"&gt;&lt;/a&gt; _ =&amp;gt; &lt;span class="pp"&gt;panic!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;Not supported on types with `self`!&amp;quot;&lt;/span&gt;),&lt;/span&gt;
421&lt;span id="cb26-9"&gt;&lt;a href="#cb26-9" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 453&lt;span id="cb26-9"&gt;&lt;a href="#cb26-9"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
422&lt;span id="cb26-10"&gt;&lt;a href="#cb26-10" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 454&lt;span id="cb26-10"&gt;&lt;a href="#cb26-10"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
423&lt;span id="cb26-11"&gt;&lt;a href="#cb26-11" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 455&lt;span id="cb26-11"&gt;&lt;a href="#cb26-11"&gt;&lt;/a&gt;&lt;/span&gt;
424&lt;span id="cb26-12"&gt;&lt;a href="#cb26-12" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; extract_arg_types(fn_args&lt;span class="op"&gt;:&lt;/span&gt; Punctuated&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;FnArg&lt;span class="op"&gt;,&lt;/span&gt; &lt;span class="pp"&gt;syn::token::&lt;/span&gt;Comma&lt;span class="op"&gt;&amp;gt;&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;Vec&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;&lt;span class="dt"&gt;Box&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;Type&lt;span class="op"&gt;&amp;gt;&amp;gt;&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 456&lt;span id="cb26-12"&gt;&lt;a href="#cb26-12"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; extract_arg_types(fn_args: Punctuated&amp;lt;FnArg, &lt;span class="pp"&gt;syn::token::&lt;/span&gt;Comma&amp;gt;) -&amp;gt; &lt;span class="dt"&gt;Vec&lt;/span&gt;&amp;lt;&lt;span class="dt"&gt;Box&lt;/span&gt;&amp;lt;Type&amp;gt;&amp;gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
425&lt;span id="cb26-13"&gt;&lt;a href="#cb26-13" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; fn_args&lt;span class="op"&gt;.&lt;/span&gt;into_iter()&lt;span class="op"&gt;.&lt;/span&gt;map(extract_type)&lt;span class="op"&gt;.&lt;/span&gt;&lt;span class="pp"&gt;collect::&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;&lt;span class="dt"&gt;Vec&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;_&lt;span class="op"&gt;&amp;gt;&amp;gt;&lt;/span&gt;()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 457&lt;span id="cb26-13"&gt;&lt;a href="#cb26-13"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; fn_args.into_iter().map(extract_type).&lt;span class="pp"&gt;collect::&lt;/span&gt;&amp;lt;&lt;span class="dt"&gt;Vec&lt;/span&gt;&amp;lt;_&amp;gt;&amp;gt;();&lt;/span&gt;
426&lt;span id="cb26-14"&gt;&lt;a href="#cb26-14" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 458&lt;span id="cb26-14"&gt;&lt;a href="#cb26-14"&gt;&lt;/a&gt;&lt;/span&gt;
427&lt;span id="cb26-15"&gt;&lt;a href="#cb26-15" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 459&lt;span id="cb26-15"&gt;&lt;a href="#cb26-15"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
428&lt;p&gt;A good reader would have looked at the docs for output member of the &lt;code&gt;syn::Signature&lt;/code&gt; struct. It has the type &lt;code&gt;syn::ReturnType&lt;/code&gt;. So there is no extraction to do here right? There are actually a couple of things we have to ensure here:&lt;/p&gt; 460&lt;p&gt;A good reader would have looked at the docs for output member of the &lt;code&gt;syn::Signature&lt;/code&gt; struct. It has the type &lt;code&gt;syn::ReturnType&lt;/code&gt;. So there is no extraction to do here right? There are actually a couple of things we have to ensure here:&lt;/p&gt;
429&lt;ol type="1"&gt; 461&lt;ol type="1"&gt;
430&lt;li&gt;&lt;p&gt;We need to ensure that the function returns! A function that does not return is pointless in this case, and I will tell you why, in the &lt;a href="#notes"&gt;Notes&lt;/a&gt; section.&lt;/p&gt;&lt;/li&gt; 462&lt;li&gt;&lt;p&gt;We need to ensure that the function returns! A function that does not return is pointless in this case, and I will tell you why, in the &lt;a href="#notes"&gt;Notes&lt;/a&gt; section.&lt;/p&gt;&lt;/li&gt;
431&lt;li&gt;&lt;p&gt;A &lt;code&gt;ReturnType&lt;/code&gt; encloses the arrow of the return as well, we need to get rid of that. Recall:&lt;/p&gt; 463&lt;li&gt;&lt;p&gt;A &lt;code&gt;ReturnType&lt;/code&gt; encloses the arrow of the return as well, we need to get rid of that. Recall:&lt;/p&gt;
432&lt;div class="sourceCode" id="cb27"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb27-1"&gt;&lt;a href="#cb27-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;/span&gt; 464&lt;div class="sourceCode" id="cb27"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb27-1"&gt;&lt;a href="#cb27-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 = &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;/span&gt;
433&lt;span id="cb27-2"&gt;&lt;a href="#cb27-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// and not&lt;/span&gt;&lt;/span&gt; 465&lt;span id="cb27-2"&gt;&lt;a href="#cb27-2"&gt;&lt;/a&gt;&lt;span class="co"&gt;// and not&lt;/span&gt;&lt;/span&gt;
434&lt;span id="cb27-3"&gt;&lt;a href="#cb27-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;/li&gt; 466&lt;span id="cb27-3"&gt;&lt;a href="#cb27-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 = -&amp;gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;&lt;/li&gt;
435&lt;/ol&gt; 467&lt;/ol&gt;
436&lt;p&gt;Here is the snippet that handles extraction of the return type (doc: &lt;a href="https://docs.rs/syn/1.0.19/syn/enum.ReturnType.html"&gt;syn::ReturnType&lt;/a&gt;):&lt;/p&gt; 468&lt;p&gt;Here is the snippet that handles extraction of the return type (doc: &lt;a href="https://docs.rs/syn/1.0.19/syn/enum.ReturnType.html"&gt;syn::ReturnType&lt;/a&gt;):&lt;/p&gt;
437&lt;div class="sourceCode" id="cb28"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb28-1"&gt;&lt;a href="#cb28-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt; 469&lt;div class="sourceCode" id="cb28"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb28-1"&gt;&lt;a href="#cb28-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
438&lt;span id="cb28-2"&gt;&lt;a href="#cb28-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 470&lt;span id="cb28-2"&gt;&lt;a href="#cb28-2"&gt;&lt;/a&gt;&lt;/span&gt;
439&lt;span id="cb28-3"&gt;&lt;a href="#cb28-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; extract_return_type(a&lt;span class="op"&gt;:&lt;/span&gt; ReturnType) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;Box&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;Type&lt;span class="op"&gt;&amp;gt;&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 471&lt;span id="cb28-3"&gt;&lt;a href="#cb28-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; extract_return_type(a: ReturnType) -&amp;gt; &lt;span class="dt"&gt;Box&lt;/span&gt;&amp;lt;Type&amp;gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
440&lt;span id="cb28-4"&gt;&lt;a href="#cb28-4" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;match&lt;/span&gt; a &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 472&lt;span id="cb28-4"&gt;&lt;a href="#cb28-4"&gt;&lt;/a&gt; &lt;span class="kw"&gt;match&lt;/span&gt; a &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
441&lt;span id="cb28-5"&gt;&lt;a href="#cb28-5" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="pp"&gt;ReturnType::&lt;/span&gt;Type(_&lt;span class="op"&gt;,&lt;/span&gt; p) &lt;span class="op"&gt;=&amp;gt;&lt;/span&gt; p&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt; 473&lt;span id="cb28-5"&gt;&lt;a href="#cb28-5"&gt;&lt;/a&gt; &lt;span class="pp"&gt;ReturnType::&lt;/span&gt;Type(_, p) =&amp;gt; p,&lt;/span&gt;
442&lt;span id="cb28-6"&gt;&lt;a href="#cb28-6" aria-hidden="true"&gt;&lt;/a&gt; _ &lt;span class="op"&gt;=&amp;gt;&lt;/span&gt; &lt;span class="pp"&gt;panic!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;Not supported on functions without return types!&amp;quot;&lt;/span&gt;)&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt; 474&lt;span id="cb28-6"&gt;&lt;a href="#cb28-6"&gt;&lt;/a&gt; _ =&amp;gt; &lt;span class="pp"&gt;panic!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;Not supported on functions without return types!&amp;quot;&lt;/span&gt;),&lt;/span&gt;
443&lt;span id="cb28-7"&gt;&lt;a href="#cb28-7" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 475&lt;span id="cb28-7"&gt;&lt;a href="#cb28-7"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
444&lt;span id="cb28-8"&gt;&lt;a href="#cb28-8" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 476&lt;span id="cb28-8"&gt;&lt;a href="#cb28-8"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
445&lt;p&gt;You might notice that we are making extensive use of the &lt;code&gt;panic!&lt;/code&gt; macro. Well, that is because it is a good idea to quit on receiving an unsatisfactory &lt;code&gt;TokenStream&lt;/code&gt;.&lt;/p&gt; 477&lt;p&gt;You might notice that we are making extensive use of the &lt;code&gt;panic!&lt;/code&gt; macro. Well, that is because it is a good idea to quit on receiving an unsatisfactory &lt;code&gt;TokenStream&lt;/code&gt;.&lt;/p&gt;
446&lt;p&gt;With all our types ready, we can get on with generating type aliases:&lt;/p&gt; 478&lt;p&gt;With all our types ready, we can get on with generating type aliases:&lt;/p&gt;
447&lt;div class="sourceCode" id="cb29"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb29-1"&gt;&lt;a href="#cb29-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt; 479&lt;div class="sourceCode" id="cb29"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb29-1"&gt;&lt;a href="#cb29-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
448&lt;span id="cb29-2"&gt;&lt;a href="#cb29-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 480&lt;span id="cb29-2"&gt;&lt;a href="#cb29-2"&gt;&lt;/a&gt;&lt;/span&gt;
449&lt;span id="cb29-3"&gt;&lt;a href="#cb29-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;quote::&lt;/span&gt;&lt;span class="op"&gt;{&lt;/span&gt;quote&lt;span class="op"&gt;,&lt;/span&gt; format_ident&lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt; 481&lt;span id="cb29-3"&gt;&lt;a href="#cb29-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;quote::&lt;/span&gt;&lt;span class="op"&gt;{&lt;/span&gt;quote, format_ident&lt;span class="op"&gt;}&lt;/span&gt;;&lt;/span&gt;
450&lt;span id="cb29-4"&gt;&lt;a href="#cb29-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 482&lt;span id="cb29-4"&gt;&lt;a href="#cb29-4"&gt;&lt;/a&gt;&lt;/span&gt;
451&lt;span id="cb29-5"&gt;&lt;a href="#cb29-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; generate_type_aliases(&lt;/span&gt; 483&lt;span id="cb29-5"&gt;&lt;a href="#cb29-5"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; generate_type_aliases(&lt;/span&gt;
452&lt;span id="cb29-6"&gt;&lt;a href="#cb29-6" aria-hidden="true"&gt;&lt;/a&gt; fn_arg_types&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="op"&gt;&amp;amp;&lt;/span&gt;[&lt;span class="dt"&gt;Box&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;Type&lt;span class="op"&gt;&amp;gt;&lt;/span&gt;]&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt; 484&lt;span id="cb29-6"&gt;&lt;a href="#cb29-6"&gt;&lt;/a&gt; fn_arg_types: &amp;amp;&lt;span class="op"&gt;[&lt;/span&gt;&lt;span class="dt"&gt;Box&lt;/span&gt;&amp;lt;Type&amp;gt;&lt;span class="op"&gt;]&lt;/span&gt;,&lt;/span&gt;
453&lt;span id="cb29-7"&gt;&lt;a href="#cb29-7" aria-hidden="true"&gt;&lt;/a&gt; fn_return_type&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;Box&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;Type&lt;span class="op"&gt;&amp;gt;,&lt;/span&gt;&lt;/span&gt; 485&lt;span id="cb29-7"&gt;&lt;a href="#cb29-7"&gt;&lt;/a&gt; fn_return_type: &lt;span class="dt"&gt;Box&lt;/span&gt;&amp;lt;Type&amp;gt;,&lt;/span&gt;
454&lt;span id="cb29-8"&gt;&lt;a href="#cb29-8" aria-hidden="true"&gt;&lt;/a&gt; fn_name&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="op"&gt;&amp;amp;&lt;/span&gt;&lt;span class="pp"&gt;syn::&lt;/span&gt;Ident&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt; 486&lt;span id="cb29-8"&gt;&lt;a href="#cb29-8"&gt;&lt;/a&gt; fn_name: &amp;amp;&lt;span class="pp"&gt;syn::&lt;/span&gt;Ident,&lt;/span&gt;
455&lt;span id="cb29-9"&gt;&lt;a href="#cb29-9" aria-hidden="true"&gt;&lt;/a&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;Vec&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;&lt;span class="pp"&gt;proc_macro2::&lt;/span&gt;TokenStream&lt;span class="op"&gt;&amp;gt;&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt; &lt;span class="co"&gt;// 1&lt;/span&gt;&lt;/span&gt; 487&lt;span id="cb29-9"&gt;&lt;a href="#cb29-9"&gt;&lt;/a&gt;) -&amp;gt; &lt;span class="dt"&gt;Vec&lt;/span&gt;&amp;lt;&lt;span class="pp"&gt;proc_macro2::&lt;/span&gt;TokenStream&amp;gt; &lt;span class="op"&gt;{&lt;/span&gt; &lt;span class="co"&gt;// 1&lt;/span&gt;&lt;/span&gt;
456&lt;span id="cb29-10"&gt;&lt;a href="#cb29-10" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 488&lt;span id="cb29-10"&gt;&lt;a href="#cb29-10"&gt;&lt;/a&gt;&lt;/span&gt;
457&lt;span id="cb29-11"&gt;&lt;a href="#cb29-11" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; type_t0 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="pp"&gt;format_ident!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;_{}_T0&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; fn_name)&lt;span class="op"&gt;;&lt;/span&gt; &lt;span class="co"&gt;// 2&lt;/span&gt;&lt;/span&gt; 489&lt;span id="cb29-11"&gt;&lt;a href="#cb29-11"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; type_t0 = &lt;span class="pp"&gt;format_ident!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;_{}_T0&amp;quot;&lt;/span&gt;, fn_name); &lt;span class="co"&gt;// 2&lt;/span&gt;&lt;/span&gt;
458&lt;span id="cb29-12"&gt;&lt;a href="#cb29-12" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; &lt;span class="kw"&gt;mut&lt;/span&gt; type_aliases &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="pp"&gt;vec!&lt;/span&gt;[&lt;span class="pp"&gt;quote!&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt; &lt;span class="kw"&gt;type&lt;/span&gt; #type_t0 &lt;span class="op"&gt;=&lt;/span&gt; #fn_return_type &lt;span class="op"&gt;}&lt;/span&gt;]&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 490&lt;span id="cb29-12"&gt;&lt;a href="#cb29-12"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; &lt;span class="kw"&gt;mut&lt;/span&gt; type_aliases = &lt;span class="pp"&gt;vec!&lt;/span&gt;&lt;span class="op"&gt;[&lt;/span&gt;&lt;span class="pp"&gt;quote!&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt; &lt;span class="kw"&gt;type&lt;/span&gt; #type_t0 = #fn_return_type &lt;span class="op"&gt;}]&lt;/span&gt;;&lt;/span&gt;
459&lt;span id="cb29-13"&gt;&lt;a href="#cb29-13" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 491&lt;span id="cb29-13"&gt;&lt;a href="#cb29-13"&gt;&lt;/a&gt;&lt;/span&gt;
460&lt;span id="cb29-14"&gt;&lt;a href="#cb29-14" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="co"&gt;// 3&lt;/span&gt;&lt;/span&gt; 492&lt;span id="cb29-14"&gt;&lt;a href="#cb29-14"&gt;&lt;/a&gt; &lt;span class="co"&gt;// 3&lt;/span&gt;&lt;/span&gt;
461&lt;span id="cb29-15"&gt;&lt;a href="#cb29-15" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;for&lt;/span&gt; (i&lt;span class="op"&gt;,&lt;/span&gt; t) &lt;span class="kw"&gt;in&lt;/span&gt; (&lt;span class="dv"&gt;1&lt;/span&gt;&lt;span class="op"&gt;..&lt;/span&gt;)&lt;span class="op"&gt;.&lt;/span&gt;zip(fn_arg_types&lt;span class="op"&gt;.&lt;/span&gt;into_iter()&lt;span class="op"&gt;.&lt;/span&gt;rev()) &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 493&lt;span id="cb29-15"&gt;&lt;a href="#cb29-15"&gt;&lt;/a&gt; &lt;span class="kw"&gt;for&lt;/span&gt; (i, t) &lt;span class="kw"&gt;in&lt;/span&gt; (&lt;span class="dv"&gt;1&lt;/span&gt;..).zip(fn_arg_types.into_iter().rev()) &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
462&lt;span id="cb29-16"&gt;&lt;a href="#cb29-16" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; p &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="pp"&gt;format_ident!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;_{}_{}&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; fn_name&lt;span class="op"&gt;,&lt;/span&gt; &lt;span class="pp"&gt;format!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;T{}&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; i &lt;span class="op"&gt;-&lt;/span&gt; &lt;span class="dv"&gt;1&lt;/span&gt;))&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 494&lt;span id="cb29-16"&gt;&lt;a href="#cb29-16"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; p = &lt;span class="pp"&gt;format_ident!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;_{}_{}&amp;quot;&lt;/span&gt;, fn_name, &lt;span class="pp"&gt;format!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;T{}&amp;quot;&lt;/span&gt;, i - &lt;span class="dv"&gt;1&lt;/span&gt;));&lt;/span&gt;
463&lt;span id="cb29-17"&gt;&lt;a href="#cb29-17" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; n &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="pp"&gt;format_ident!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;_{}_{}&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; fn_name&lt;span class="op"&gt;,&lt;/span&gt; &lt;span class="pp"&gt;format!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;T{}&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; i))&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 495&lt;span id="cb29-17"&gt;&lt;a href="#cb29-17"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; n = &lt;span class="pp"&gt;format_ident!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;_{}_{}&amp;quot;&lt;/span&gt;, fn_name, &lt;span class="pp"&gt;format!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;T{}&amp;quot;&lt;/span&gt;, i));&lt;/span&gt;
464&lt;span id="cb29-18"&gt;&lt;a href="#cb29-18" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 496&lt;span id="cb29-18"&gt;&lt;a href="#cb29-18"&gt;&lt;/a&gt;&lt;/span&gt;
465&lt;span id="cb29-19"&gt;&lt;a href="#cb29-19" aria-hidden="true"&gt;&lt;/a&gt; type_aliases&lt;span class="op"&gt;.&lt;/span&gt;push(&lt;span class="pp"&gt;quote!&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 497&lt;span id="cb29-19"&gt;&lt;a href="#cb29-19"&gt;&lt;/a&gt; type_aliases.push(&lt;span class="pp"&gt;quote!&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
466&lt;span id="cb29-20"&gt;&lt;a href="#cb29-20" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;type&lt;/span&gt; #n &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(#t) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; #p&lt;/span&gt; 498&lt;span id="cb29-20"&gt;&lt;a href="#cb29-20"&gt;&lt;/a&gt; &lt;span class="kw"&gt;type&lt;/span&gt; #n = &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(#t) -&amp;gt; #p&lt;/span&gt;
467&lt;span id="cb29-21"&gt;&lt;a href="#cb29-21" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 499&lt;span id="cb29-21"&gt;&lt;a href="#cb29-21"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;);&lt;/span&gt;
468&lt;span id="cb29-22"&gt;&lt;a href="#cb29-22" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 500&lt;span id="cb29-22"&gt;&lt;a href="#cb29-22"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
469&lt;span id="cb29-23"&gt;&lt;a href="#cb29-23" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 501&lt;span id="cb29-23"&gt;&lt;a href="#cb29-23"&gt;&lt;/a&gt;&lt;/span&gt;
470&lt;span id="cb29-24"&gt;&lt;a href="#cb29-24" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; type_aliases&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 502&lt;span id="cb29-24"&gt;&lt;a href="#cb29-24"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; type_aliases;&lt;/span&gt;
471&lt;span id="cb29-25"&gt;&lt;a href="#cb29-25" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 503&lt;span id="cb29-25"&gt;&lt;a href="#cb29-25"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
472&lt;p&gt;&lt;strong&gt;1. The return value&lt;/strong&gt;&lt;br /&gt; 504&lt;p&gt;&lt;strong&gt;1. The return value&lt;/strong&gt;&lt;br /&gt;
473We are returning a &lt;code&gt;Vec&amp;lt;proc_macro2::TokenStream&amp;gt;&lt;/code&gt;, i. e., a list of &lt;code&gt;TokenStream&lt;/code&gt;s, where each item is a type alias.&lt;/p&gt; 505We are returning a &lt;code&gt;Vec&amp;lt;proc_macro2::TokenStream&amp;gt;&lt;/code&gt;, i. e., a list of &lt;code&gt;TokenStream&lt;/code&gt;s, where each item is a type alias.&lt;/p&gt;
474&lt;p&gt;&lt;strong&gt;2. Format identifier?&lt;/strong&gt;&lt;br /&gt; 506&lt;p&gt;&lt;strong&gt;2. Format identifier?&lt;/strong&gt;&lt;br /&gt;
475I’ve got some explanation to do on this line. Clearly, we are trying to write the first type alias, and initialize our &lt;code&gt;TokenStream&lt;/code&gt; vector with &lt;code&gt;T0&lt;/code&gt;, because it is different from the others:&lt;/p&gt; 507I’ve got some explanation to do on this line. Clearly, we are trying to write the first type alias, and initialize our &lt;code&gt;TokenStream&lt;/code&gt; vector with &lt;code&gt;T0&lt;/code&gt;, because it is different from the others:&lt;/p&gt;
476&lt;div class="sourceCode" id="cb30"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb30-1"&gt;&lt;a href="#cb30-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 &lt;span class="op"&gt;=&lt;/span&gt; something&lt;/span&gt; 508&lt;div class="sourceCode" id="cb30"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb30-1"&gt;&lt;a href="#cb30-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 = something&lt;/span&gt;
477&lt;span id="cb30-2"&gt;&lt;a href="#cb30-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// the others are of the form&lt;/span&gt;&lt;/span&gt; 509&lt;span id="cb30-2"&gt;&lt;a href="#cb30-2"&gt;&lt;/a&gt;&lt;span class="co"&gt;// the others are of the form&lt;/span&gt;&lt;/span&gt;
478&lt;span id="cb30-3"&gt;&lt;a href="#cb30-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; Tr &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(something) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; something&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 510&lt;span id="cb30-3"&gt;&lt;a href="#cb30-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; Tr = &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(something) -&amp;gt; something&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
479&lt;p&gt;&lt;code&gt;format_ident!&lt;/code&gt; is similar to &lt;code&gt;format!&lt;/code&gt;. Instead of returning a formatted string, it returns a &lt;code&gt;syn::Ident&lt;/code&gt;. Therefore, &lt;code&gt;type_t0&lt;/code&gt; is actually an identifier for, in the case of our &lt;code&gt;add&lt;/code&gt; function, &lt;code&gt;_add_T0&lt;/code&gt;. Why is this formatting important? Namespacing.&lt;/p&gt; 511&lt;p&gt;&lt;code&gt;format_ident!&lt;/code&gt; is similar to &lt;code&gt;format!&lt;/code&gt;. Instead of returning a formatted string, it returns a &lt;code&gt;syn::Ident&lt;/code&gt;. Therefore, &lt;code&gt;type_t0&lt;/code&gt; is actually an identifier for, in the case of our &lt;code&gt;add&lt;/code&gt; function, &lt;code&gt;_add_T0&lt;/code&gt;. Why is this formatting important? Namespacing.&lt;/p&gt;
480&lt;p&gt;Picture this, we have two functions, &lt;code&gt;add&lt;/code&gt; and &lt;code&gt;subtract&lt;/code&gt;, that we wish to curry with our macro:&lt;/p&gt; 512&lt;p&gt;Picture this, we have two functions, &lt;code&gt;add&lt;/code&gt; and &lt;code&gt;subtract&lt;/code&gt;, that we wish to curry with our macro:&lt;/p&gt;
481&lt;div class="sourceCode" id="cb31"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb31-1"&gt;&lt;a href="#cb31-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;curry&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt; 513&lt;div class="sourceCode" id="cb31"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb31-1"&gt;&lt;a href="#cb31-1"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;curry&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt;
482&lt;span id="cb31-2"&gt;&lt;a href="#cb31-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add(&lt;span class="op"&gt;...&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt; &lt;span class="op"&gt;...&lt;/span&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 514&lt;span id="cb31-2"&gt;&lt;a href="#cb31-2"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add(...) -&amp;gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt; ... &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
483&lt;span id="cb31-3"&gt;&lt;a href="#cb31-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 515&lt;span id="cb31-3"&gt;&lt;a href="#cb31-3"&gt;&lt;/a&gt;&lt;/span&gt;
484&lt;span id="cb31-4"&gt;&lt;a href="#cb31-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;curry&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt; 516&lt;span id="cb31-4"&gt;&lt;a href="#cb31-4"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;curry&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt;
485&lt;span id="cb31-5"&gt;&lt;a href="#cb31-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; sub(&lt;span class="op"&gt;...&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt; &lt;span class="op"&gt;...&lt;/span&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 517&lt;span id="cb31-5"&gt;&lt;a href="#cb31-5"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; sub(...) -&amp;gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt; ... &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
486&lt;p&gt;Here is the same but with macros expanded:&lt;/p&gt; 518&lt;p&gt;Here is the same but with macros expanded:&lt;/p&gt;
487&lt;div class="sourceCode" id="cb32"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb32-1"&gt;&lt;a href="#cb32-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 519&lt;div class="sourceCode" id="cb32"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb32-1"&gt;&lt;a href="#cb32-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 = &lt;span class="dt"&gt;u32&lt;/span&gt;;&lt;/span&gt;
488&lt;span id="cb32-2"&gt;&lt;a href="#cb32-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T1 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; T0&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 520&lt;span id="cb32-2"&gt;&lt;a href="#cb32-2"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T1 = &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; T0;&lt;/span&gt;
489&lt;span id="cb32-3"&gt;&lt;a href="#cb32-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add( &lt;span class="op"&gt;...&lt;/span&gt; ) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; T1 &lt;span class="op"&gt;{&lt;/span&gt; &lt;span class="op"&gt;...&lt;/span&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 521&lt;span id="cb32-3"&gt;&lt;a href="#cb32-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add( ... ) -&amp;gt; T1 &lt;span class="op"&gt;{&lt;/span&gt; ... &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
490&lt;span id="cb32-4"&gt;&lt;a href="#cb32-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 522&lt;span id="cb32-4"&gt;&lt;a href="#cb32-4"&gt;&lt;/a&gt;&lt;/span&gt;
491&lt;span id="cb32-5"&gt;&lt;a href="#cb32-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 523&lt;span id="cb32-5"&gt;&lt;a href="#cb32-5"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T0 = &lt;span class="dt"&gt;u32&lt;/span&gt;;&lt;/span&gt;
492&lt;span id="cb32-6"&gt;&lt;a href="#cb32-6" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T1 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; T0&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 524&lt;span id="cb32-6"&gt;&lt;a href="#cb32-6"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; T1 = &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; T0;&lt;/span&gt;
493&lt;span id="cb32-7"&gt;&lt;a href="#cb32-7" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; sub( &lt;span class="op"&gt;...&lt;/span&gt; ) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; T1 &lt;span class="op"&gt;{&lt;/span&gt; &lt;span class="op"&gt;...&lt;/span&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 525&lt;span id="cb32-7"&gt;&lt;a href="#cb32-7"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; sub( ... ) -&amp;gt; T1 &lt;span class="op"&gt;{&lt;/span&gt; ... &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
494&lt;p&gt;We end up with two definitions of &lt;code&gt;T0&lt;/code&gt;! Now, if we do the little &lt;code&gt;format_ident!&lt;/code&gt; dance we did up there:&lt;/p&gt; 526&lt;p&gt;We end up with two definitions of &lt;code&gt;T0&lt;/code&gt;! Now, if we do the little &lt;code&gt;format_ident!&lt;/code&gt; dance we did up there:&lt;/p&gt;
495&lt;div class="sourceCode" id="cb33"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb33-1"&gt;&lt;a href="#cb33-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; _add_T0 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 527&lt;div class="sourceCode" id="cb33"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb33-1"&gt;&lt;a href="#cb33-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; _add_T0 = &lt;span class="dt"&gt;u32&lt;/span&gt;;&lt;/span&gt;
496&lt;span id="cb33-2"&gt;&lt;a href="#cb33-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; _add_T1 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; _add_T0&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 528&lt;span id="cb33-2"&gt;&lt;a href="#cb33-2"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; _add_T1 = &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; _add_T0;&lt;/span&gt;
497&lt;span id="cb33-3"&gt;&lt;a href="#cb33-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add( &lt;span class="op"&gt;...&lt;/span&gt; ) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; _add_T1 &lt;span class="op"&gt;{&lt;/span&gt; &lt;span class="op"&gt;...&lt;/span&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 529&lt;span id="cb33-3"&gt;&lt;a href="#cb33-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add( ... ) -&amp;gt; _add_T1 &lt;span class="op"&gt;{&lt;/span&gt; ... &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
498&lt;span id="cb33-4"&gt;&lt;a href="#cb33-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 530&lt;span id="cb33-4"&gt;&lt;a href="#cb33-4"&gt;&lt;/a&gt;&lt;/span&gt;
499&lt;span id="cb33-5"&gt;&lt;a href="#cb33-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; _sub_T0 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 531&lt;span id="cb33-5"&gt;&lt;a href="#cb33-5"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; _sub_T0 = &lt;span class="dt"&gt;u32&lt;/span&gt;;&lt;/span&gt;
500&lt;span id="cb33-6"&gt;&lt;a href="#cb33-6" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; _sub_T1 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; _sub_T0&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 532&lt;span id="cb33-6"&gt;&lt;a href="#cb33-6"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; _sub_T1 = &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; _sub_T0;&lt;/span&gt;
501&lt;span id="cb33-7"&gt;&lt;a href="#cb33-7" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; sub( &lt;span class="op"&gt;...&lt;/span&gt; ) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; _sub_T1 &lt;span class="op"&gt;{&lt;/span&gt; &lt;span class="op"&gt;...&lt;/span&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 533&lt;span id="cb33-7"&gt;&lt;a href="#cb33-7"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; sub( ... ) -&amp;gt; _sub_T1 &lt;span class="op"&gt;{&lt;/span&gt; ... &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
502&lt;p&gt;Voilà! The type aliases don’t tread on each other. Remember to import &lt;code&gt;format_ident&lt;/code&gt; from the &lt;code&gt;quote&lt;/code&gt; crate.&lt;/p&gt; 534&lt;p&gt;Voilà! The type aliases don’t tread on each other. Remember to import &lt;code&gt;format_ident&lt;/code&gt; from the &lt;code&gt;quote&lt;/code&gt; crate.&lt;/p&gt;
503&lt;p&gt;&lt;strong&gt;3. The TokenStream Vector&lt;/strong&gt;&lt;/p&gt; 535&lt;p&gt;&lt;strong&gt;3. The TokenStream Vector&lt;/strong&gt;&lt;/p&gt;
504&lt;p&gt;We iterate over our types in reverse order (&lt;code&gt;T0&lt;/code&gt; is the last return, &lt;code&gt;T1&lt;/code&gt; is the second last, so on), assign a number to each iteration with &lt;code&gt;zip&lt;/code&gt;, generate type names with &lt;code&gt;format_ident&lt;/code&gt;, push a &lt;code&gt;TokenStream&lt;/code&gt; with the help of &lt;code&gt;quote&lt;/code&gt; and variable interpolation.&lt;/p&gt; 536&lt;p&gt;We iterate over our types in reverse order (&lt;code&gt;T0&lt;/code&gt; is the last return, &lt;code&gt;T1&lt;/code&gt; is the second last, so on), assign a number to each iteration with &lt;code&gt;zip&lt;/code&gt;, generate type names with &lt;code&gt;format_ident&lt;/code&gt;, push a &lt;code&gt;TokenStream&lt;/code&gt; with the help of &lt;code&gt;quote&lt;/code&gt; and variable interpolation.&lt;/p&gt;
505&lt;p&gt;If you are wondering why we used &lt;code&gt;(1..).zip()&lt;/code&gt; instead of &lt;code&gt;.enumerate()&lt;/code&gt;, it’s because we wanted to start counting from 1 instead of 0 (we are already done with &lt;code&gt;T0&lt;/code&gt;!).&lt;/p&gt; 537&lt;p&gt;If you are wondering why we used &lt;code&gt;(1..).zip()&lt;/code&gt; instead of &lt;code&gt;.enumerate()&lt;/code&gt;, it’s because we wanted to start counting from 1 instead of 0 (we are already done with &lt;code&gt;T0&lt;/code&gt;!).&lt;/p&gt;
506&lt;h4 id="getting-it-together"&gt;Getting it together&lt;/h4&gt; 538&lt;h4 id="getting-it-together"&gt;Getting it together&lt;/h4&gt;
507&lt;p&gt;I promised we’d have a fully working macro by the end of last section. I lied, we have to tie everything together in our &lt;code&gt;generate_curry&lt;/code&gt; function:&lt;/p&gt; 539&lt;p&gt;I promised we’d have a fully working macro by the end of last section. I lied, we have to tie everything together in our &lt;code&gt;generate_curry&lt;/code&gt; function:&lt;/p&gt;
508&lt;div class="sourceCode" id="cb34"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb34-1"&gt;&lt;a href="#cb34-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt; 540&lt;div class="sourceCode" id="cb34"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb34-1"&gt;&lt;a href="#cb34-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
509&lt;span id="cb34-2"&gt;&lt;a href="#cb34-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 541&lt;span id="cb34-2"&gt;&lt;a href="#cb34-2"&gt;&lt;/a&gt;&lt;/span&gt;
510&lt;span id="cb34-3"&gt;&lt;a href="#cb34-3" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;fn&lt;/span&gt; generate_curry(parsed&lt;span class="op"&gt;:&lt;/span&gt; ItemFn) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="pp"&gt;proc_macro2::&lt;/span&gt;TokenStream &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 542&lt;span id="cb34-3"&gt;&lt;a href="#cb34-3"&gt;&lt;/a&gt; &lt;span class="kw"&gt;fn&lt;/span&gt; generate_curry(parsed: ItemFn) -&amp;gt; &lt;span class="pp"&gt;proc_macro2::&lt;/span&gt;TokenStream &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
511&lt;span id="cb34-4"&gt;&lt;a href="#cb34-4" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_body &lt;span class="op"&gt;=&lt;/span&gt; parsed&lt;span class="op"&gt;.&lt;/span&gt;block&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 543&lt;span id="cb34-4"&gt;&lt;a href="#cb34-4"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_body = parsed.block;&lt;/span&gt;
512&lt;span id="cb34-5"&gt;&lt;a href="#cb34-5" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; sig &lt;span class="op"&gt;=&lt;/span&gt; parsed&lt;span class="op"&gt;.&lt;/span&gt;sig&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 544&lt;span id="cb34-5"&gt;&lt;a href="#cb34-5"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; sig = parsed.sig;&lt;/span&gt;
513&lt;span id="cb34-6"&gt;&lt;a href="#cb34-6" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; vis &lt;span class="op"&gt;=&lt;/span&gt; parsed&lt;span class="op"&gt;.&lt;/span&gt;vis&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 545&lt;span id="cb34-6"&gt;&lt;a href="#cb34-6"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; vis = parsed.vis;&lt;/span&gt;
514&lt;span id="cb34-7"&gt;&lt;a href="#cb34-7" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_name &lt;span class="op"&gt;=&lt;/span&gt; sig&lt;span class="op"&gt;.&lt;/span&gt;ident&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 546&lt;span id="cb34-7"&gt;&lt;a href="#cb34-7"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_name = sig.ident;&lt;/span&gt;
515&lt;span id="cb34-8"&gt;&lt;a href="#cb34-8" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_args &lt;span class="op"&gt;=&lt;/span&gt; sig&lt;span class="op"&gt;.&lt;/span&gt;inputs&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 547&lt;span id="cb34-8"&gt;&lt;a href="#cb34-8"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_args = sig.inputs;&lt;/span&gt;
516&lt;span id="cb34-9"&gt;&lt;a href="#cb34-9" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_return_type &lt;span class="op"&gt;=&lt;/span&gt; sig&lt;span class="op"&gt;.&lt;/span&gt;output&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 548&lt;span id="cb34-9"&gt;&lt;a href="#cb34-9"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; fn_return_type = sig.output;&lt;/span&gt;
517&lt;span id="cb34-10"&gt;&lt;a href="#cb34-10" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 549&lt;span id="cb34-10"&gt;&lt;a href="#cb34-10"&gt;&lt;/a&gt;&lt;/span&gt;
518&lt;span id="cb34-11"&gt;&lt;a href="#cb34-11" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; arg_idents &lt;span class="op"&gt;=&lt;/span&gt; extract_arg_idents(fn_args&lt;span class="op"&gt;.&lt;/span&gt;clone())&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 550&lt;span id="cb34-11"&gt;&lt;a href="#cb34-11"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; arg_idents = extract_arg_idents(fn_args.clone());&lt;/span&gt;
519&lt;span id="cb34-12"&gt;&lt;a href="#cb34-12" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; first_ident &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;&amp;amp;&lt;/span&gt;arg_idents&lt;span class="op"&gt;.&lt;/span&gt;first()&lt;span class="op"&gt;.&lt;/span&gt;unwrap()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 551&lt;span id="cb34-12"&gt;&lt;a href="#cb34-12"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; first_ident = &amp;amp;arg_idents.first().unwrap();&lt;/span&gt;
520&lt;span id="cb34-13"&gt;&lt;a href="#cb34-13" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; curried_body &lt;span class="op"&gt;=&lt;/span&gt; generate_body(&lt;span class="op"&gt;&amp;amp;&lt;/span&gt;arg_idents[&lt;span class="dv"&gt;1&lt;/span&gt;&lt;span class="op"&gt;..&lt;/span&gt;]&lt;span class="op"&gt;,&lt;/span&gt; fn_body&lt;span class="op"&gt;.&lt;/span&gt;clone())&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 552&lt;span id="cb34-13"&gt;&lt;a href="#cb34-13"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; curried_body = generate_body(&amp;amp;arg_idents&lt;span class="op"&gt;[&lt;/span&gt;&lt;span class="dv"&gt;1&lt;/span&gt;..&lt;span class="op"&gt;]&lt;/span&gt;, fn_body.clone());&lt;/span&gt;
521&lt;span id="cb34-14"&gt;&lt;a href="#cb34-14" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 553&lt;span id="cb34-14"&gt;&lt;a href="#cb34-14"&gt;&lt;/a&gt;&lt;/span&gt;
522&lt;span id="cb34-15"&gt;&lt;a href="#cb34-15" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="kw"&gt;let&lt;/span&gt; arg_types &lt;span class="op"&gt;=&lt;/span&gt; extract_arg_types(fn_args&lt;span class="op"&gt;.&lt;/span&gt;clone())&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 554&lt;span id="cb34-15"&gt;&lt;a href="#cb34-15"&gt;&lt;/a&gt;+ &lt;span class="kw"&gt;let&lt;/span&gt; arg_types = extract_arg_types(fn_args.clone());&lt;/span&gt;
523&lt;span id="cb34-16"&gt;&lt;a href="#cb34-16" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="kw"&gt;let&lt;/span&gt; first_type &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;&amp;amp;&lt;/span&gt;arg_types&lt;span class="op"&gt;.&lt;/span&gt;first()&lt;span class="op"&gt;.&lt;/span&gt;unwrap()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 555&lt;span id="cb34-16"&gt;&lt;a href="#cb34-16"&gt;&lt;/a&gt;+ &lt;span class="kw"&gt;let&lt;/span&gt; first_type = &amp;amp;arg_types.first().unwrap();&lt;/span&gt;
524&lt;span id="cb34-17"&gt;&lt;a href="#cb34-17" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="kw"&gt;let&lt;/span&gt; type_aliases &lt;span class="op"&gt;=&lt;/span&gt; generate_type_aliases(&lt;/span&gt; 556&lt;span id="cb34-17"&gt;&lt;a href="#cb34-17"&gt;&lt;/a&gt;+ &lt;span class="kw"&gt;let&lt;/span&gt; type_aliases = generate_type_aliases(&lt;/span&gt;
525&lt;span id="cb34-18"&gt;&lt;a href="#cb34-18" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="op"&gt;&amp;amp;&lt;/span&gt;arg_types[&lt;span class="dv"&gt;1&lt;/span&gt;&lt;span class="op"&gt;..&lt;/span&gt;]&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt; 557&lt;span id="cb34-18"&gt;&lt;a href="#cb34-18"&gt;&lt;/a&gt;+ &amp;amp;arg_types&lt;span class="op"&gt;[&lt;/span&gt;&lt;span class="dv"&gt;1&lt;/span&gt;..&lt;span class="op"&gt;]&lt;/span&gt;,&lt;/span&gt;
526&lt;span id="cb34-19"&gt;&lt;a href="#cb34-19" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; extract_return_type(fn_return_type)&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt; 558&lt;span id="cb34-19"&gt;&lt;a href="#cb34-19"&gt;&lt;/a&gt;+ extract_return_type(fn_return_type),&lt;/span&gt;
527&lt;span id="cb34-20"&gt;&lt;a href="#cb34-20" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="op"&gt;&amp;amp;&lt;/span&gt;fn_name&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt; 559&lt;span id="cb34-20"&gt;&lt;a href="#cb34-20"&gt;&lt;/a&gt;+ &amp;amp;fn_name,&lt;/span&gt;
528&lt;span id="cb34-21"&gt;&lt;a href="#cb34-21" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; )&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 560&lt;span id="cb34-21"&gt;&lt;a href="#cb34-21"&gt;&lt;/a&gt;+ );&lt;/span&gt;
529&lt;span id="cb34-22"&gt;&lt;a href="#cb34-22" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 561&lt;span id="cb34-22"&gt;&lt;a href="#cb34-22"&gt;&lt;/a&gt;&lt;/span&gt;
530&lt;span id="cb34-23"&gt;&lt;a href="#cb34-23" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="kw"&gt;let&lt;/span&gt; return_type &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="pp"&gt;format_ident!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;_{}_{}&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; &lt;span class="op"&gt;&amp;amp;&lt;/span&gt;fn_name&lt;span class="op"&gt;,&lt;/span&gt; &lt;span class="pp"&gt;format!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;T{}&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; type_aliases&lt;span class="op"&gt;.&lt;/span&gt;len() &lt;span class="op"&gt;-&lt;/span&gt; &lt;span class="dv"&gt;1&lt;/span&gt;))&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 562&lt;span id="cb34-23"&gt;&lt;a href="#cb34-23"&gt;&lt;/a&gt;+ &lt;span class="kw"&gt;let&lt;/span&gt; return_type = &lt;span class="pp"&gt;format_ident!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;_{}_{}&amp;quot;&lt;/span&gt;, &amp;amp;fn_name, &lt;span class="pp"&gt;format!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;T{}&amp;quot;&lt;/span&gt;, type_aliases.len() - &lt;span class="dv"&gt;1&lt;/span&gt;));&lt;/span&gt;
531&lt;span id="cb34-24"&gt;&lt;a href="#cb34-24" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 563&lt;span id="cb34-24"&gt;&lt;a href="#cb34-24"&gt;&lt;/a&gt;&lt;/span&gt;
532&lt;span id="cb34-25"&gt;&lt;a href="#cb34-25" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="pp"&gt;quote!&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 564&lt;span id="cb34-25"&gt;&lt;a href="#cb34-25"&gt;&lt;/a&gt;+ &lt;span class="kw"&gt;return&lt;/span&gt; &lt;span class="pp"&gt;quote!&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
533&lt;span id="cb34-26"&gt;&lt;a href="#cb34-26" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; #(#type_aliases)&lt;span class="op"&gt;;*&lt;/span&gt; &lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 565&lt;span id="cb34-26"&gt;&lt;a href="#cb34-26"&gt;&lt;/a&gt;+ #(#type_aliases);* ;&lt;/span&gt;
534&lt;span id="cb34-27"&gt;&lt;a href="#cb34-27" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; #vis &lt;span class="kw"&gt;fn&lt;/span&gt; #fn_name (#first_ident&lt;span class="op"&gt;:&lt;/span&gt; #first_type) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; #return_type &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 566&lt;span id="cb34-27"&gt;&lt;a href="#cb34-27"&gt;&lt;/a&gt;+ #vis &lt;span class="kw"&gt;fn&lt;/span&gt; #fn_name (#first_ident: #first_type) -&amp;gt; #return_type &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
535&lt;span id="cb34-28"&gt;&lt;a href="#cb34-28" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; #curried_body &lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 567&lt;span id="cb34-28"&gt;&lt;a href="#cb34-28"&gt;&lt;/a&gt;+ #curried_body ;&lt;/span&gt;
536&lt;span id="cb34-29"&gt;&lt;a href="#cb34-29" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 568&lt;span id="cb34-29"&gt;&lt;a href="#cb34-29"&gt;&lt;/a&gt;+ &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
537&lt;span id="cb34-30"&gt;&lt;a href="#cb34-30" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt; 569&lt;span id="cb34-30"&gt;&lt;a href="#cb34-30"&gt;&lt;/a&gt;+ &lt;span class="op"&gt;}&lt;/span&gt;;&lt;/span&gt;
538&lt;span id="cb34-31"&gt;&lt;a href="#cb34-31" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 570&lt;span id="cb34-31"&gt;&lt;a href="#cb34-31"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
539&lt;p&gt;Most of the additions are self explanatory, I’ll go through the return statement with you. We are returning a &lt;code&gt;quote!{ ... }&lt;/code&gt;, so a &lt;code&gt;proc_macro2::TokenStream&lt;/code&gt;. We are iterating through the &lt;code&gt;type_aliases&lt;/code&gt; variable, which you might recall, is a &lt;code&gt;Vec&amp;lt;TokenStream&amp;gt;&lt;/code&gt;. You might notice the sneaky semicolon before the &lt;code&gt;*&lt;/code&gt;. This basically tells &lt;code&gt;quote&lt;/code&gt;, to insert an item, then a semicolon, and then the next one, another semicolon, and so on. The semicolon is a separator. We need to manually insert another semicolon at the end of it all, &lt;code&gt;quote&lt;/code&gt; doesn’t insert a separator at the end of the iteration.&lt;/p&gt; 571&lt;p&gt;Most of the additions are self explanatory, I’ll go through the return statement with you. We are returning a &lt;code&gt;quote!{ ... }&lt;/code&gt;, so a &lt;code&gt;proc_macro2::TokenStream&lt;/code&gt;. We are iterating through the &lt;code&gt;type_aliases&lt;/code&gt; variable, which you might recall, is a &lt;code&gt;Vec&amp;lt;TokenStream&amp;gt;&lt;/code&gt;. You might notice the sneaky semicolon before the &lt;code&gt;*&lt;/code&gt;. This basically tells &lt;code&gt;quote&lt;/code&gt;, to insert an item, then a semicolon, and then the next one, another semicolon, and so on. The semicolon is a separator. We need to manually insert another semicolon at the end of it all, &lt;code&gt;quote&lt;/code&gt; doesn’t insert a separator at the end of the iteration.&lt;/p&gt;
540&lt;p&gt;We retain the visibility and name of our original function. Our curried function takes as args, just the first argument of our original function. The return type of our curried function is actually, the last type alias we create. If you think back to our manually curried &lt;code&gt;add&lt;/code&gt; function, we returned &lt;code&gt;T2&lt;/code&gt;, which was in fact, the last type alias we created.&lt;/p&gt; 572&lt;p&gt;We retain the visibility and name of our original function. Our curried function takes as args, just the first argument of our original function. The return type of our curried function is actually, the last type alias we create. If you think back to our manually curried &lt;code&gt;add&lt;/code&gt; function, we returned &lt;code&gt;T2&lt;/code&gt;, which was in fact, the last type alias we created.&lt;/p&gt;
541&lt;p&gt;I am sure, at this point, you are itching to test this out, but before that, let me introduce you to some good methods of debugging proc-macro code.&lt;/p&gt; 573&lt;p&gt;I am sure, at this point, you are itching to test this out, but before that, let me introduce you to some good methods of debugging proc-macro code.&lt;/p&gt;
@@ -567,57 +599,57 @@ fn main() {
567&lt;p&gt;Writing proc-macros without &lt;code&gt;cargo-expand&lt;/code&gt; is tantamount to driving a vehicle without rear view mirrors! Keep an eye on what is going on behind your back.&lt;/p&gt; 599&lt;p&gt;Writing proc-macros without &lt;code&gt;cargo-expand&lt;/code&gt; is tantamount to driving a vehicle without rear view mirrors! Keep an eye on what is going on behind your back.&lt;/p&gt;
568&lt;p&gt;Now, your macro won’t always compile, you might just recieve the bee movie script as an error. &lt;code&gt;cargo-expand&lt;/code&gt; will not work in such cases. I would suggest printing out your variables to inspect them. &lt;code&gt;TokenStream&lt;/code&gt; implements &lt;code&gt;Display&lt;/code&gt; as well as &lt;code&gt;Debug&lt;/code&gt;. We don’t always have to be respectable programmers. Just print it.&lt;/p&gt; 600&lt;p&gt;Now, your macro won’t always compile, you might just recieve the bee movie script as an error. &lt;code&gt;cargo-expand&lt;/code&gt; will not work in such cases. I would suggest printing out your variables to inspect them. &lt;code&gt;TokenStream&lt;/code&gt; implements &lt;code&gt;Display&lt;/code&gt; as well as &lt;code&gt;Debug&lt;/code&gt;. We don’t always have to be respectable programmers. Just print it.&lt;/p&gt;
569&lt;p&gt;Enough of that, lets get testing:&lt;/p&gt; 601&lt;p&gt;Enough of that, lets get testing:&lt;/p&gt;
570&lt;div class="sourceCode" id="cb37"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb37-1"&gt;&lt;a href="#cb37-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// tests/smoke.rs&lt;/span&gt;&lt;/span&gt; 602&lt;div class="sourceCode" id="cb37"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb37-1"&gt;&lt;a href="#cb37-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// tests/smoke.rs&lt;/span&gt;&lt;/span&gt;
571&lt;span id="cb37-2"&gt;&lt;a href="#cb37-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 603&lt;span id="cb37-2"&gt;&lt;a href="#cb37-2"&gt;&lt;/a&gt;&lt;/span&gt;
572&lt;span id="cb37-3"&gt;&lt;a href="#cb37-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="at"&gt;#![&lt;/span&gt;feature&lt;span class="at"&gt;(&lt;/span&gt;type_alias_impl_trait&lt;span class="at"&gt;)]&lt;/span&gt;&lt;/span&gt; 604&lt;span id="cb37-3"&gt;&lt;a href="#cb37-3"&gt;&lt;/a&gt;&lt;span class="at"&gt;#![&lt;/span&gt;feature&lt;span class="at"&gt;(&lt;/span&gt;type_alias_impl_trait&lt;span class="at"&gt;)]&lt;/span&gt;&lt;/span&gt;
573&lt;span id="cb37-4"&gt;&lt;a href="#cb37-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 605&lt;span id="cb37-4"&gt;&lt;a href="#cb37-4"&gt;&lt;/a&gt;&lt;/span&gt;
574&lt;span id="cb37-5"&gt;&lt;a href="#cb37-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;&lt;span class="pp"&gt;crate_name::&lt;/span&gt;curry&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt; 606&lt;span id="cb37-5"&gt;&lt;a href="#cb37-5"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;&lt;span class="pp"&gt;crate_name::&lt;/span&gt;curry&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt;
575&lt;span id="cb37-6"&gt;&lt;a href="#cb37-6" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add(x&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; y&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; z&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 607&lt;span id="cb37-6"&gt;&lt;a href="#cb37-6"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add(x: &lt;span class="dt"&gt;u32&lt;/span&gt;, y: &lt;span class="dt"&gt;u32&lt;/span&gt;, z: &lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
576&lt;span id="cb37-7"&gt;&lt;a href="#cb37-7" aria-hidden="true"&gt;&lt;/a&gt; x &lt;span class="op"&gt;+&lt;/span&gt; y &lt;span class="op"&gt;+&lt;/span&gt; z&lt;/span&gt; 608&lt;span id="cb37-7"&gt;&lt;a href="#cb37-7"&gt;&lt;/a&gt; x + y + z&lt;/span&gt;
577&lt;span id="cb37-8"&gt;&lt;a href="#cb37-8" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 609&lt;span id="cb37-8"&gt;&lt;a href="#cb37-8"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
578&lt;span id="cb37-9"&gt;&lt;a href="#cb37-9" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 610&lt;span id="cb37-9"&gt;&lt;a href="#cb37-9"&gt;&lt;/a&gt;&lt;/span&gt;
579&lt;span id="cb37-10"&gt;&lt;a href="#cb37-10" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;test&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt; 611&lt;span id="cb37-10"&gt;&lt;a href="#cb37-10"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;test&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt;
580&lt;span id="cb37-11"&gt;&lt;a href="#cb37-11" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; works() &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 612&lt;span id="cb37-11"&gt;&lt;a href="#cb37-11"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; works() &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
581&lt;span id="cb37-12"&gt;&lt;a href="#cb37-12" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="pp"&gt;assert_eq!&lt;/span&gt;(&lt;span class="dv"&gt;15&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; add(&lt;span class="dv"&gt;4&lt;/span&gt;)(&lt;span class="dv"&gt;5&lt;/span&gt;)(&lt;span class="dv"&gt;6&lt;/span&gt;))&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 613&lt;span id="cb37-12"&gt;&lt;a href="#cb37-12"&gt;&lt;/a&gt; &lt;span class="pp"&gt;assert_eq!&lt;/span&gt;(&lt;span class="dv"&gt;15&lt;/span&gt;, add(&lt;span class="dv"&gt;4&lt;/span&gt;)(&lt;span class="dv"&gt;5&lt;/span&gt;)(&lt;span class="dv"&gt;6&lt;/span&gt;));&lt;/span&gt;
582&lt;span id="cb37-13"&gt;&lt;a href="#cb37-13" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 614&lt;span id="cb37-13"&gt;&lt;a href="#cb37-13"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
583&lt;p&gt;Run &lt;code&gt;cargo +nightly test&lt;/code&gt;. You should see a pleasing message:&lt;/p&gt; 615&lt;p&gt;Run &lt;code&gt;cargo +nightly test&lt;/code&gt;. You should see a pleasing message:&lt;/p&gt;
584&lt;pre&gt;&lt;code&gt;running 1 test 616&lt;pre&gt;&lt;code&gt;running 1 test
585test tests::works ... ok&lt;/code&gt;&lt;/pre&gt; 617test tests::works ... ok&lt;/code&gt;&lt;/pre&gt;
586&lt;p&gt;Take a look at the expansion for our curry macro, via &lt;code&gt;cargo +nightly expand --tests smoke&lt;/code&gt;:&lt;/p&gt; 618&lt;p&gt;Take a look at the expansion for our curry macro, via &lt;code&gt;cargo +nightly expand --tests smoke&lt;/code&gt;:&lt;/p&gt;
587&lt;div class="sourceCode" id="cb39"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb39-1"&gt;&lt;a href="#cb39-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; _add_T0 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 619&lt;div class="sourceCode" id="cb39"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb39-1"&gt;&lt;a href="#cb39-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; _add_T0 = &lt;span class="dt"&gt;u32&lt;/span&gt;;&lt;/span&gt;
588&lt;span id="cb39-2"&gt;&lt;a href="#cb39-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; _add_T1 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; _add_T0&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 620&lt;span id="cb39-2"&gt;&lt;a href="#cb39-2"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; _add_T1 = &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; _add_T0;&lt;/span&gt;
589&lt;span id="cb39-3"&gt;&lt;a href="#cb39-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; _add_T2 &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; _add_T1&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 621&lt;span id="cb39-3"&gt;&lt;a href="#cb39-3"&gt;&lt;/a&gt;&lt;span class="kw"&gt;type&lt;/span&gt; _add_T2 = &lt;span class="kw"&gt;impl&lt;/span&gt; &lt;span class="bu"&gt;Fn&lt;/span&gt;(&lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; _add_T1;&lt;/span&gt;
590&lt;span id="cb39-4"&gt;&lt;a href="#cb39-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add(x&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; _add_T2 &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 622&lt;span id="cb39-4"&gt;&lt;a href="#cb39-4"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; add(x: &lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; _add_T2 &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
591&lt;span id="cb39-5"&gt;&lt;a href="#cb39-5" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; (&lt;span class="kw"&gt;move&lt;/span&gt; &lt;span class="op"&gt;|&lt;/span&gt;y&lt;span class="op"&gt;|&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 623&lt;span id="cb39-5"&gt;&lt;a href="#cb39-5"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; (&lt;span class="kw"&gt;move&lt;/span&gt; |y| &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
592&lt;span id="cb39-6"&gt;&lt;a href="#cb39-6" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;move&lt;/span&gt; &lt;span class="op"&gt;|&lt;/span&gt;z&lt;span class="op"&gt;|&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 624&lt;span id="cb39-6"&gt;&lt;a href="#cb39-6"&gt;&lt;/a&gt; &lt;span class="kw"&gt;move&lt;/span&gt; |z| &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
593&lt;span id="cb39-7"&gt;&lt;a href="#cb39-7" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; x &lt;span class="op"&gt;+&lt;/span&gt; y &lt;span class="op"&gt;+&lt;/span&gt; z&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 625&lt;span id="cb39-7"&gt;&lt;a href="#cb39-7"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; x + y + z;&lt;/span&gt;
594&lt;span id="cb39-8"&gt;&lt;a href="#cb39-8" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 626&lt;span id="cb39-8"&gt;&lt;a href="#cb39-8"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
595&lt;span id="cb39-9"&gt;&lt;a href="#cb39-9" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 627&lt;span id="cb39-9"&gt;&lt;a href="#cb39-9"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;);&lt;/span&gt;
596&lt;span id="cb39-10"&gt;&lt;a href="#cb39-10" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 628&lt;span id="cb39-10"&gt;&lt;a href="#cb39-10"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
597&lt;span id="cb39-11"&gt;&lt;a href="#cb39-11" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 629&lt;span id="cb39-11"&gt;&lt;a href="#cb39-11"&gt;&lt;/a&gt;&lt;/span&gt;
598&lt;span id="cb39-12"&gt;&lt;a href="#cb39-12" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;// a bunch of other stuff generated by #[test] and assert_eq!&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 630&lt;span id="cb39-12"&gt;&lt;a href="#cb39-12"&gt;&lt;/a&gt;&lt;span class="co"&gt;// a bunch of other stuff generated by #[test] and assert_eq!&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
599&lt;p&gt;A sight for sore eyes.&lt;/p&gt; 631&lt;p&gt;A sight for sore eyes.&lt;/p&gt;
600&lt;p&gt;Here is a more complex example that generates ten multiples of the first ten natural numbers:&lt;/p&gt; 632&lt;p&gt;Here is a more complex example that generates ten multiples of the first ten natural numbers:&lt;/p&gt;
601&lt;div class="sourceCode" id="cb40"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb40-1"&gt;&lt;a href="#cb40-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;curry&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt; 633&lt;div class="sourceCode" id="cb40"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb40-1"&gt;&lt;a href="#cb40-1"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;curry&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt;
602&lt;span id="cb40-2"&gt;&lt;a href="#cb40-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; product(x&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; y&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt;) &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 634&lt;span id="cb40-2"&gt;&lt;a href="#cb40-2"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; product(x: &lt;span class="dt"&gt;u32&lt;/span&gt;, y: &lt;span class="dt"&gt;u32&lt;/span&gt;) -&amp;gt; &lt;span class="dt"&gt;u32&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
603&lt;span id="cb40-3"&gt;&lt;a href="#cb40-3" aria-hidden="true"&gt;&lt;/a&gt; x &lt;span class="op"&gt;*&lt;/span&gt; y&lt;/span&gt; 635&lt;span id="cb40-3"&gt;&lt;a href="#cb40-3"&gt;&lt;/a&gt; x * y&lt;/span&gt;
604&lt;span id="cb40-4"&gt;&lt;a href="#cb40-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 636&lt;span id="cb40-4"&gt;&lt;a href="#cb40-4"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
605&lt;span id="cb40-5"&gt;&lt;a href="#cb40-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 637&lt;span id="cb40-5"&gt;&lt;a href="#cb40-5"&gt;&lt;/a&gt;&lt;/span&gt;
606&lt;span id="cb40-6"&gt;&lt;a href="#cb40-6" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; multiples() &lt;span class="op"&gt;-&amp;gt;&lt;/span&gt; &lt;span class="dt"&gt;Vec&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;&lt;span class="dt"&gt;Vec&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;&lt;span class="dt"&gt;u32&lt;/span&gt;&lt;span class="op"&gt;&amp;gt;&amp;gt;{&lt;/span&gt;&lt;/span&gt; 638&lt;span id="cb40-6"&gt;&lt;a href="#cb40-6"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; multiples() -&amp;gt; &lt;span class="dt"&gt;Vec&lt;/span&gt;&amp;lt;&lt;span class="dt"&gt;Vec&lt;/span&gt;&amp;lt;&lt;span class="dt"&gt;u32&lt;/span&gt;&amp;gt;&amp;gt;&lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
607&lt;span id="cb40-7"&gt;&lt;a href="#cb40-7" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; v &lt;span class="op"&gt;=&lt;/span&gt; (&lt;span class="dv"&gt;1&lt;/span&gt;&lt;span class="op"&gt;..=&lt;/span&gt;&lt;span class="dv"&gt;10&lt;/span&gt;)&lt;span class="op"&gt;.&lt;/span&gt;map(product)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 639&lt;span id="cb40-7"&gt;&lt;a href="#cb40-7"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; v = (&lt;span class="dv"&gt;1&lt;/span&gt;..=&lt;span class="dv"&gt;10&lt;/span&gt;).map(product);&lt;/span&gt;
608&lt;span id="cb40-8"&gt;&lt;a href="#cb40-8" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; (&lt;span class="dv"&gt;1&lt;/span&gt;&lt;span class="op"&gt;..=&lt;/span&gt;&lt;span class="dv"&gt;10&lt;/span&gt;)&lt;/span&gt; 640&lt;span id="cb40-8"&gt;&lt;a href="#cb40-8"&gt;&lt;/a&gt; &lt;span class="kw"&gt;return&lt;/span&gt; (&lt;span class="dv"&gt;1&lt;/span&gt;..=&lt;span class="dv"&gt;10&lt;/span&gt;)&lt;/span&gt;
609&lt;span id="cb40-9"&gt;&lt;a href="#cb40-9" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;.&lt;/span&gt;map(&lt;span class="op"&gt;|&lt;/span&gt;x&lt;span class="op"&gt;|&lt;/span&gt; v&lt;span class="op"&gt;.&lt;/span&gt;clone()&lt;span class="op"&gt;.&lt;/span&gt;map(&lt;span class="op"&gt;|&lt;/span&gt;f&lt;span class="op"&gt;|&lt;/span&gt; f(x))&lt;span class="op"&gt;.&lt;/span&gt;collect())&lt;/span&gt; 641&lt;span id="cb40-9"&gt;&lt;a href="#cb40-9"&gt;&lt;/a&gt; .map(|x| v.clone().map(|f| f(x)).collect())&lt;/span&gt;
610&lt;span id="cb40-10"&gt;&lt;a href="#cb40-10" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;.&lt;/span&gt;collect()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 642&lt;span id="cb40-10"&gt;&lt;a href="#cb40-10"&gt;&lt;/a&gt; .collect();&lt;/span&gt;
611&lt;span id="cb40-11"&gt;&lt;a href="#cb40-11" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 643&lt;span id="cb40-11"&gt;&lt;a href="#cb40-11"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
612&lt;h3 id="notes"&gt;Notes&lt;/h3&gt; 644&lt;h3 id="notes"&gt;Notes&lt;/h3&gt;
613&lt;p&gt;I didn’t quite explain why we use &lt;code&gt;move |arg|&lt;/code&gt; in our closure. This is because we want to take ownership of the variable supplied to us. Take a look at this example:&lt;/p&gt; 645&lt;p&gt;I didn’t quite explain why we use &lt;code&gt;move |arg|&lt;/code&gt; in our closure. This is because we want to take ownership of the variable supplied to us. Take a look at this example:&lt;/p&gt;
614&lt;div class="sourceCode" id="cb41"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb41-1"&gt;&lt;a href="#cb41-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; v &lt;span class="op"&gt;=&lt;/span&gt; add(&lt;span class="dv"&gt;5&lt;/span&gt;)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 646&lt;div class="sourceCode" id="cb41"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb41-1"&gt;&lt;a href="#cb41-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; v = add(&lt;span class="dv"&gt;5&lt;/span&gt;);&lt;/span&gt;
615&lt;span id="cb41-2"&gt;&lt;a href="#cb41-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; g&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 647&lt;span id="cb41-2"&gt;&lt;a href="#cb41-2"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; g;&lt;/span&gt;
616&lt;span id="cb41-3"&gt;&lt;a href="#cb41-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 648&lt;span id="cb41-3"&gt;&lt;a href="#cb41-3"&gt;&lt;/a&gt;&lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
617&lt;span id="cb41-4"&gt;&lt;a href="#cb41-4" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; x &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="dv"&gt;5&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 649&lt;span id="cb41-4"&gt;&lt;a href="#cb41-4"&gt;&lt;/a&gt; &lt;span class="kw"&gt;let&lt;/span&gt; x = &lt;span class="dv"&gt;5&lt;/span&gt;;&lt;/span&gt;
618&lt;span id="cb41-5"&gt;&lt;a href="#cb41-5" aria-hidden="true"&gt;&lt;/a&gt; g &lt;span class="op"&gt;=&lt;/span&gt; v(x)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 650&lt;span id="cb41-5"&gt;&lt;a href="#cb41-5"&gt;&lt;/a&gt; g = v(x);&lt;/span&gt;
619&lt;span id="cb41-6"&gt;&lt;a href="#cb41-6" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt; 651&lt;span id="cb41-6"&gt;&lt;a href="#cb41-6"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
620&lt;span id="cb41-7"&gt;&lt;a href="#cb41-7" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="pp"&gt;println!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;{}&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; g(&lt;span class="dv"&gt;2&lt;/span&gt;))&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 652&lt;span id="cb41-7"&gt;&lt;a href="#cb41-7"&gt;&lt;/a&gt;&lt;span class="pp"&gt;println!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;{}&amp;quot;&lt;/span&gt;, g(&lt;span class="dv"&gt;2&lt;/span&gt;));&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
621&lt;p&gt;Variable &lt;code&gt;x&lt;/code&gt; goes out of scope before &lt;code&gt;g&lt;/code&gt; can return a concrete value. If we take ownership of &lt;code&gt;x&lt;/code&gt; by &lt;code&gt;move&lt;/code&gt;ing it into our closure, we can expect this to work reliably. In fact, rustc understands this, and forces you to use &lt;code&gt;move&lt;/code&gt;.&lt;/p&gt; 653&lt;p&gt;Variable &lt;code&gt;x&lt;/code&gt; goes out of scope before &lt;code&gt;g&lt;/code&gt; can return a concrete value. If we take ownership of &lt;code&gt;x&lt;/code&gt; by &lt;code&gt;move&lt;/code&gt;ing it into our closure, we can expect this to work reliably. In fact, rustc understands this, and forces you to use &lt;code&gt;move&lt;/code&gt;.&lt;/p&gt;
622&lt;p&gt;This usage of &lt;code&gt;move&lt;/code&gt; is exactly why &lt;strong&gt;a curried function without a return is useless&lt;/strong&gt;. Every variable we pass to our curried function gets moved into its local scope. Playing with these variables cannot cause a change outside this scope. Returning is our only method of interaction with anything beyond this function.&lt;/p&gt; 654&lt;p&gt;This usage of &lt;code&gt;move&lt;/code&gt; is exactly why &lt;strong&gt;a curried function without a return is useless&lt;/strong&gt;. Every variable we pass to our curried function gets moved into its local scope. Playing with these variables cannot cause a change outside this scope. Returning is our only method of interaction with anything beyond this function.&lt;/p&gt;
623&lt;h3 id="conclusion"&gt;Conclusion&lt;/h3&gt; 655&lt;h3 id="conclusion"&gt;Conclusion&lt;/h3&gt;
@@ -632,7 +664,7 @@ test tests::works ... ok&lt;/code&gt;&lt;/pre&gt;
632&lt;/ol&gt; 664&lt;/ol&gt;
633&lt;/section&gt;</description> 665&lt;/section&gt;</description>
634<link>https://peppe.rs/posts/auto-currying_rust_functions/</link> 666<link>https://peppe.rs/posts/auto-currying_rust_functions/</link>
635<pubDate>Sat, 09 May 2020 06:12:00 +0000</pubDate> 667<pubDate>Fri, 08 May 2020 18:30:00 +0000</pubDate>
636<guid>https://peppe.rs/posts/auto-currying_rust_functions/</guid> 668<guid>https://peppe.rs/posts/auto-currying_rust_functions/</guid>
637</item> 669</item>
638<item> 670<item>
@@ -687,41 +719,41 @@ test tests::works ... ok&lt;/code&gt;&lt;/pre&gt;
687&lt;p&gt;Hold on, why is it so tiny? Well, that’s because our canvas was 100x100, head over to &lt;code&gt;Image &amp;gt; Scale Image&lt;/code&gt;, set &lt;code&gt;Quality &amp;gt; Interpolation&lt;/code&gt; to &lt;code&gt;None&lt;/code&gt; and scale it up to 700x700, et voilà!&lt;/p&gt; 719&lt;p&gt;Hold on, why is it so tiny? Well, that’s because our canvas was 100x100, head over to &lt;code&gt;Image &amp;gt; Scale Image&lt;/code&gt;, set &lt;code&gt;Quality &amp;gt; Interpolation&lt;/code&gt; to &lt;code&gt;None&lt;/code&gt; and scale it up to 700x700, et voilà!&lt;/p&gt;
688&lt;p&gt;&lt;img src="https://u.peppe.rs/CH.png" /&gt;&lt;/p&gt;</description> 720&lt;p&gt;&lt;img src="https://u.peppe.rs/CH.png" /&gt;&lt;/p&gt;</description>
689<link>https://peppe.rs/posts/pixel_art_in_GIMP/</link> 721<link>https://peppe.rs/posts/pixel_art_in_GIMP/</link>
690<pubDate>Thu, 09 Apr 2020 16:28:00 +0000</pubDate> 722<pubDate>Wed, 08 Apr 2020 18:30:00 +0000</pubDate>
691<guid>https://peppe.rs/posts/pixel_art_in_GIMP/</guid> 723<guid>https://peppe.rs/posts/pixel_art_in_GIMP/</guid>
692</item> 724</item>
693<item> 725<item>
694<title>Rapid Refactoring With Vim</title> 726<title>Rapid Refactoring With Vim</title>
695<description>&lt;p&gt;Last weekend, I was tasked with refactoring the 96 unit tests on &lt;a href="https://github.com/ruma/ruma-events/pull/70"&gt;ruma-events&lt;/a&gt; to use strictly typed json objects using &lt;code&gt;serde_json::json!&lt;/code&gt; instead of raw strings. It was rather painless thanks to vim :)&lt;/p&gt; 727<description>&lt;p&gt;Last weekend, I was tasked with refactoring the 96 unit tests on &lt;a href="https://github.com/ruma/ruma-events/pull/70"&gt;ruma-events&lt;/a&gt; to use strictly typed json objects using &lt;code&gt;serde_json::json!&lt;/code&gt; instead of raw strings. It was rather painless thanks to vim :)&lt;/p&gt;
696&lt;p&gt;Here’s a small sample of what had to be done (note the lines prefixed with the arrow):&lt;/p&gt; 728&lt;p&gt;Here’s a small sample of what had to be done (note the lines prefixed with the arrow):&lt;/p&gt;
697&lt;div class="sourceCode" id="cb1"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb1-1"&gt;&lt;a href="#cb1-1" aria-hidden="true"&gt;&lt;/a&gt;→ &lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;serde_json::&lt;/span&gt;&lt;span class="op"&gt;{&lt;/span&gt;from_str&lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt; 729&lt;div class="sourceCode" id="cb1"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb1-1"&gt;&lt;a href="#cb1-1"&gt;&lt;/a&gt;→ &lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;serde_json::&lt;/span&gt;&lt;span class="op"&gt;{&lt;/span&gt;from_str&lt;span class="op"&gt;}&lt;/span&gt;;&lt;/span&gt;
698&lt;span id="cb1-2"&gt;&lt;a href="#cb1-2" aria-hidden="true"&gt;&lt;/a&gt; &lt;/span&gt; 730&lt;span id="cb1-2"&gt;&lt;a href="#cb1-2"&gt;&lt;/a&gt; &lt;/span&gt;
699&lt;span id="cb1-3"&gt;&lt;a href="#cb1-3" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="at"&gt;#[&lt;/span&gt;test&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt; 731&lt;span id="cb1-3"&gt;&lt;a href="#cb1-3"&gt;&lt;/a&gt; &lt;span class="at"&gt;#[&lt;/span&gt;test&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt;
700&lt;span id="cb1-4"&gt;&lt;a href="#cb1-4" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;fn&lt;/span&gt; deserialize() &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 732&lt;span id="cb1-4"&gt;&lt;a href="#cb1-4"&gt;&lt;/a&gt; &lt;span class="kw"&gt;fn&lt;/span&gt; deserialize() &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
701&lt;span id="cb1-5"&gt;&lt;a href="#cb1-5" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="pp"&gt;assert_eq!&lt;/span&gt;(&lt;/span&gt; 733&lt;span id="cb1-5"&gt;&lt;a href="#cb1-5"&gt;&lt;/a&gt; &lt;span class="pp"&gt;assert_eq!&lt;/span&gt;(&lt;/span&gt;
702&lt;span id="cb1-6"&gt;&lt;a href="#cb1-6" aria-hidden="true"&gt;&lt;/a&gt;→ &lt;span class="pp"&gt;from_str::&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;Action&lt;span class="op"&gt;&amp;gt;&lt;/span&gt;(&lt;span class="st"&gt;r#&amp;quot;{&amp;quot;set_tweak&amp;quot;: &amp;quot;highlight&amp;quot;}&amp;quot;#),&lt;/span&gt;&lt;/span&gt; 734&lt;span id="cb1-6"&gt;&lt;a href="#cb1-6"&gt;&lt;/a&gt;→ &lt;span class="pp"&gt;from_str::&lt;/span&gt;&amp;lt;Action&amp;gt;(&lt;span class="st"&gt;r#&amp;quot;{&amp;quot;set_tweak&amp;quot;: &amp;quot;highlight&amp;quot;}&amp;quot;#&lt;/span&gt;),&lt;/span&gt;
703&lt;span id="cb1-7"&gt;&lt;a href="#cb1-7" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="st"&gt; Action::SetTweak(Tweak::Highlight { value: true })&lt;/span&gt;&lt;/span&gt; 735&lt;span id="cb1-7"&gt;&lt;a href="#cb1-7"&gt;&lt;/a&gt; &lt;span class="pp"&gt;Action::&lt;/span&gt;SetTweak(&lt;span class="pp"&gt;Tweak::&lt;/span&gt;Highlight &lt;span class="op"&gt;{&lt;/span&gt; value: &lt;span class="cn"&gt;true&lt;/span&gt; &lt;span class="op"&gt;}&lt;/span&gt;)&lt;/span&gt;
704&lt;span id="cb1-8"&gt;&lt;a href="#cb1-8" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="st"&gt; );&lt;/span&gt;&lt;/span&gt; 736&lt;span id="cb1-8"&gt;&lt;a href="#cb1-8"&gt;&lt;/a&gt; );&lt;/span&gt;
705&lt;span id="cb1-9"&gt;&lt;a href="#cb1-9" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="st"&gt; }&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 737&lt;span id="cb1-9"&gt;&lt;a href="#cb1-9"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
706&lt;p&gt;had to be converted to:&lt;/p&gt; 738&lt;p&gt;had to be converted to:&lt;/p&gt;
707&lt;div class="sourceCode" id="cb2"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb2-1"&gt;&lt;a href="#cb2-1" aria-hidden="true"&gt;&lt;/a&gt;→ &lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;serde_json::&lt;/span&gt;&lt;span class="op"&gt;{&lt;/span&gt;from_value&lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt; 739&lt;div class="sourceCode" id="cb2"&gt;&lt;pre class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb2-1"&gt;&lt;a href="#cb2-1"&gt;&lt;/a&gt;→ &lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;serde_json::&lt;/span&gt;&lt;span class="op"&gt;{&lt;/span&gt;from_value&lt;span class="op"&gt;}&lt;/span&gt;;&lt;/span&gt;
708&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2" aria-hidden="true"&gt;&lt;/a&gt; &lt;/span&gt; 740&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2"&gt;&lt;/a&gt; &lt;/span&gt;
709&lt;span id="cb2-3"&gt;&lt;a href="#cb2-3" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="at"&gt;#[&lt;/span&gt;test&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt; 741&lt;span id="cb2-3"&gt;&lt;a href="#cb2-3"&gt;&lt;/a&gt; &lt;span class="at"&gt;#[&lt;/span&gt;test&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt;
710&lt;span id="cb2-4"&gt;&lt;a href="#cb2-4" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="kw"&gt;fn&lt;/span&gt; deserialize() &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt; 742&lt;span id="cb2-4"&gt;&lt;a href="#cb2-4"&gt;&lt;/a&gt; &lt;span class="kw"&gt;fn&lt;/span&gt; deserialize() &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
711&lt;span id="cb2-5"&gt;&lt;a href="#cb2-5" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="pp"&gt;assert_eq!&lt;/span&gt;(&lt;/span&gt; 743&lt;span id="cb2-5"&gt;&lt;a href="#cb2-5"&gt;&lt;/a&gt; &lt;span class="pp"&gt;assert_eq!&lt;/span&gt;(&lt;/span&gt;
712&lt;span id="cb2-6"&gt;&lt;a href="#cb2-6" aria-hidden="true"&gt;&lt;/a&gt;→ &lt;span class="pp"&gt;from_value::&lt;/span&gt;&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;Action&lt;span class="op"&gt;&amp;gt;&lt;/span&gt;(&lt;span class="pp"&gt;json!&lt;/span&gt;(&lt;span class="op"&gt;{&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;set_tweak&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;highlight&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;}&lt;/span&gt;))&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt; 744&lt;span id="cb2-6"&gt;&lt;a href="#cb2-6"&gt;&lt;/a&gt;→ &lt;span class="pp"&gt;from_value::&lt;/span&gt;&amp;lt;Action&amp;gt;(&lt;span class="pp"&gt;json!&lt;/span&gt;(&lt;span class="op"&gt;{&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;set_tweak&amp;quot;&lt;/span&gt;: &lt;span class="st"&gt;&amp;quot;highlight&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;}&lt;/span&gt;)),&lt;/span&gt;
713&lt;span id="cb2-7"&gt;&lt;a href="#cb2-7" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="pp"&gt;Action::&lt;/span&gt;SetTweak(&lt;span class="pp"&gt;Tweak::&lt;/span&gt;Highlight &lt;span class="op"&gt;{&lt;/span&gt; value&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="cn"&gt;true&lt;/span&gt; &lt;span class="op"&gt;}&lt;/span&gt;)&lt;/span&gt; 745&lt;span id="cb2-7"&gt;&lt;a href="#cb2-7"&gt;&lt;/a&gt; &lt;span class="pp"&gt;Action::&lt;/span&gt;SetTweak(&lt;span class="pp"&gt;Tweak::&lt;/span&gt;Highlight &lt;span class="op"&gt;{&lt;/span&gt; value: &lt;span class="cn"&gt;true&lt;/span&gt; &lt;span class="op"&gt;}&lt;/span&gt;)&lt;/span&gt;
714&lt;span id="cb2-8"&gt;&lt;a href="#cb2-8" aria-hidden="true"&gt;&lt;/a&gt; )&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt; 746&lt;span id="cb2-8"&gt;&lt;a href="#cb2-8"&gt;&lt;/a&gt; );&lt;/span&gt;
715&lt;span id="cb2-9"&gt;&lt;a href="#cb2-9" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 747&lt;span id="cb2-9"&gt;&lt;a href="#cb2-9"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
716&lt;h3 id="the-arglist"&gt;The arglist&lt;/h3&gt; 748&lt;h3 id="the-arglist"&gt;The arglist&lt;/h3&gt;
717&lt;p&gt;For the initial pass, I decided to handle imports, this was a simple find and replace operation, done to all the files containing tests. Luckily, modules (and therefore files) containing tests in Rust are annotated with the &lt;code&gt;#[cfg(test)]&lt;/code&gt; attribute. I opened all such files:&lt;/p&gt; 749&lt;p&gt;For the initial pass, I decided to handle imports, this was a simple find and replace operation, done to all the files containing tests. Luckily, modules (and therefore files) containing tests in Rust are annotated with the &lt;code&gt;#[cfg(test)]&lt;/code&gt; attribute. I opened all such files:&lt;/p&gt;
718&lt;div class="sourceCode" id="cb3"&gt;&lt;pre class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb3-1"&gt;&lt;a href="#cb3-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;# `grep -l pattern files` lists all the files&lt;/span&gt;&lt;/span&gt; 750&lt;div class="sourceCode" id="cb3"&gt;&lt;pre class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb3-1"&gt;&lt;a href="#cb3-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# `grep -l pattern files` lists all the files&lt;/span&gt;&lt;/span&gt;
719&lt;span id="cb3-2"&gt;&lt;a href="#cb3-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;# matching the pattern&lt;/span&gt;&lt;/span&gt; 751&lt;span id="cb3-2"&gt;&lt;a href="#cb3-2"&gt;&lt;/a&gt;&lt;span class="co"&gt;# matching the pattern&lt;/span&gt;&lt;/span&gt;
720&lt;span id="cb3-3"&gt;&lt;a href="#cb3-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 752&lt;span id="cb3-3"&gt;&lt;a href="#cb3-3"&gt;&lt;/a&gt;&lt;/span&gt;
721&lt;span id="cb3-4"&gt;&lt;a href="#cb3-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="ex"&gt;vim&lt;/span&gt; &lt;span class="va"&gt;$(&lt;/span&gt;&lt;span class="fu"&gt;grep&lt;/span&gt; -l &lt;span class="st"&gt;&amp;#39;cfg\(test\)&amp;#39;&lt;/span&gt; ./**/*.rs&lt;span class="va"&gt;)&lt;/span&gt;&lt;/span&gt; 753&lt;span id="cb3-4"&gt;&lt;a href="#cb3-4"&gt;&lt;/a&gt;&lt;span class="ex"&gt;vim&lt;/span&gt; &lt;span class="va"&gt;$(&lt;/span&gt;&lt;span class="fu"&gt;grep&lt;/span&gt; -l &lt;span class="st"&gt;&amp;#39;cfg\(test\)&amp;#39;&lt;/span&gt; ./**/*.rs&lt;span class="va"&gt;)&lt;/span&gt;&lt;/span&gt;
722&lt;span id="cb3-5"&gt;&lt;a href="#cb3-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 754&lt;span id="cb3-5"&gt;&lt;a href="#cb3-5"&gt;&lt;/a&gt;&lt;/span&gt;
723&lt;span id="cb3-6"&gt;&lt;a href="#cb3-6" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;# expands to something like:&lt;/span&gt;&lt;/span&gt; 755&lt;span id="cb3-6"&gt;&lt;a href="#cb3-6"&gt;&lt;/a&gt;&lt;span class="co"&gt;# expands to something like:&lt;/span&gt;&lt;/span&gt;
724&lt;span id="cb3-7"&gt;&lt;a href="#cb3-7" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="ex"&gt;vim&lt;/span&gt; push_rules.rs room/member.rs key/verification/lib.rs&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 756&lt;span id="cb3-7"&gt;&lt;a href="#cb3-7"&gt;&lt;/a&gt;&lt;span class="ex"&gt;vim&lt;/span&gt; push_rules.rs room/member.rs key/verification/lib.rs&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
725&lt;p&gt;Starting vim with more than one file at the shell prompt populates the arglist. Hit &lt;code&gt;:args&lt;/code&gt; to see the list of files currently ready to edit. The square [brackets] indicate the current file. Navigate through the arglist with &lt;code&gt;:next&lt;/code&gt; and &lt;code&gt;:prev&lt;/code&gt;. I use tpope’s vim-unimpaired &lt;a href="#fn1" class="footnote-ref" id="fnref1" role="doc-noteref"&gt;&lt;sup&gt;1&lt;/sup&gt;&lt;/a&gt;, which adds &lt;code&gt;]a&lt;/code&gt; and &lt;code&gt;[a&lt;/code&gt;, mapped to &lt;code&gt;:next&lt;/code&gt; and &lt;code&gt;:prev&lt;/code&gt;.&lt;/p&gt; 757&lt;p&gt;Starting vim with more than one file at the shell prompt populates the arglist. Hit &lt;code&gt;:args&lt;/code&gt; to see the list of files currently ready to edit. The square [brackets] indicate the current file. Navigate through the arglist with &lt;code&gt;:next&lt;/code&gt; and &lt;code&gt;:prev&lt;/code&gt;. I use tpope’s vim-unimpaired &lt;a href="#fn1" class="footnote-ref" id="fnref1" role="doc-noteref"&gt;&lt;sup&gt;1&lt;/sup&gt;&lt;/a&gt;, which adds &lt;code&gt;]a&lt;/code&gt; and &lt;code&gt;[a&lt;/code&gt;, mapped to &lt;code&gt;:next&lt;/code&gt; and &lt;code&gt;:prev&lt;/code&gt;.&lt;/p&gt;
726&lt;p&gt;All that’s left to do is the find and replace, for which we will be using vim’s &lt;code&gt;argdo&lt;/code&gt;, applying a substitution to every file in the arglist:&lt;/p&gt; 758&lt;p&gt;All that’s left to do is the find and replace, for which we will be using vim’s &lt;code&gt;argdo&lt;/code&gt;, applying a substitution to every file in the arglist:&lt;/p&gt;
727&lt;pre&gt;&lt;code&gt;:argdo s/from_str/from_value/g&lt;/code&gt;&lt;/pre&gt; 759&lt;pre&gt;&lt;code&gt;:argdo s/from_str/from_value/g&lt;/code&gt;&lt;/pre&gt;
@@ -782,7 +814,7 @@ BUFFER: json!( ... );&lt;/code&gt;&lt;/pre&gt;
782&lt;/ol&gt; 814&lt;/ol&gt;
783&lt;/section&gt;</description> 815&lt;/section&gt;</description>
784<link>https://peppe.rs/posts/rapid_refactoring_with_vim/</link> 816<link>https://peppe.rs/posts/rapid_refactoring_with_vim/</link>
785<pubDate>Wed, 01 Apr 2020 06:29:00 +0000</pubDate> 817<pubDate>Tue, 31 Mar 2020 18:30:00 +0000</pubDate>
786<guid>https://peppe.rs/posts/rapid_refactoring_with_vim/</guid> 818<guid>https://peppe.rs/posts/rapid_refactoring_with_vim/</guid>
787</item> 819</item>
788<item> 820<item>
@@ -818,7 +850,7 @@ Dimensions: 1920x1080 @ 13&amp;quot; (29.5x16.5 sq. cm)
818&lt;/ol&gt; 850&lt;/ol&gt;
819&lt;/section&gt;</description> 851&lt;/section&gt;</description>
820<link>https://peppe.rs/posts/font_size_fallacies/</link> 852<link>https://peppe.rs/posts/font_size_fallacies/</link>
821<pubDate>Tue, 17 Mar 2020 16:52:00 +0000</pubDate> 853<pubDate>Mon, 16 Mar 2020 18:30:00 +0000</pubDate>
822<guid>https://peppe.rs/posts/font_size_fallacies/</guid> 854<guid>https://peppe.rs/posts/font_size_fallacies/</guid>
823</item> 855</item>
824<item> 856<item>
@@ -842,7 +874,7 @@ mtZabXG.jpg p8d5c584f2841.jpg vjUxGjq.jpg&lt;/code&gt;&lt;/pre&gt;
842&lt;p&gt;Alright, I don’t really listen to music via &lt;code&gt;cmus&lt;/code&gt;, but I did use it a couple times when my default music player was acting up. &lt;code&gt;cmus&lt;/code&gt; is a viable option:&lt;/p&gt; 874&lt;p&gt;Alright, I don’t really listen to music via &lt;code&gt;cmus&lt;/code&gt;, but I did use it a couple times when my default music player was acting up. &lt;code&gt;cmus&lt;/code&gt; is a viable option:&lt;/p&gt;
843&lt;p&gt;&lt;a href="https://u.peppe.rs/CP.jpg"&gt;&lt;img src="https://u.peppe.rs/CP.jpg" /&gt;&lt;/a&gt;&lt;/p&gt;</description> 875&lt;p&gt;&lt;a href="https://u.peppe.rs/CP.jpg"&gt;&lt;img src="https://u.peppe.rs/CP.jpg" /&gt;&lt;/a&gt;&lt;/p&gt;</description>
844<link>https://peppe.rs/posts/termux_tandem/</link> 876<link>https://peppe.rs/posts/termux_tandem/</link>
845<pubDate>Sun, 08 Mar 2020 16:47:00 +0000</pubDate> 877<pubDate>Sat, 07 Mar 2020 18:30:00 +0000</pubDate>
846<guid>https://peppe.rs/posts/termux_tandem/</guid> 878<guid>https://peppe.rs/posts/termux_tandem/</guid>
847</item> 879</item>
848<item> 880<item>
@@ -903,26 +935,26 @@ Reading symbols from main... # yay!&lt;/code&gt;&lt;/pre&gt;
903&lt;p&gt;I chose to write in markdown, and convert to html with &lt;a href="https://kristaps.bsd.lv/lowdown/"&gt;lowdown&lt;/a&gt;.&lt;/p&gt; 935&lt;p&gt;I chose to write in markdown, and convert to html with &lt;a href="https://kristaps.bsd.lv/lowdown/"&gt;lowdown&lt;/a&gt;.&lt;/p&gt;
904&lt;h3 id="directory-structure"&gt;Directory structure&lt;/h3&gt; 936&lt;h3 id="directory-structure"&gt;Directory structure&lt;/h3&gt;
905&lt;p&gt;I host my site on GitHub pages, so &lt;code&gt;docs/&lt;/code&gt; has to be the entry point. Markdown formatted posts go into &lt;code&gt;posts/&lt;/code&gt;, get converted into html, and end up in &lt;code&gt;docs/index.html&lt;/code&gt;, something like this:&lt;/p&gt; 937&lt;p&gt;I host my site on GitHub pages, so &lt;code&gt;docs/&lt;/code&gt; has to be the entry point. Markdown formatted posts go into &lt;code&gt;posts/&lt;/code&gt;, get converted into html, and end up in &lt;code&gt;docs/index.html&lt;/code&gt;, something like this:&lt;/p&gt;
906&lt;div class="sourceCode" id="cb1"&gt;&lt;pre class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb1-1"&gt;&lt;a href="#cb1-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="va"&gt;posts=$(&lt;/span&gt;&lt;span class="fu"&gt;ls&lt;/span&gt; -t ./posts&lt;span class="va"&gt;)&lt;/span&gt; &lt;span class="co"&gt;# chronological order!&lt;/span&gt;&lt;/span&gt; 938&lt;div class="sourceCode" id="cb1"&gt;&lt;pre class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb1-1"&gt;&lt;a href="#cb1-1"&gt;&lt;/a&gt;&lt;span class="va"&gt;posts=$(&lt;/span&gt;&lt;span class="fu"&gt;ls&lt;/span&gt; -t ./posts&lt;span class="va"&gt;)&lt;/span&gt; &lt;span class="co"&gt;# chronological order!&lt;/span&gt;&lt;/span&gt;
907&lt;span id="cb1-2"&gt;&lt;a href="#cb1-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;for&lt;/span&gt; &lt;span class="ex"&gt;f&lt;/span&gt; in &lt;span class="va"&gt;$posts&lt;/span&gt;&lt;span class="kw"&gt;;&lt;/span&gt; &lt;span class="kw"&gt;do&lt;/span&gt;&lt;/span&gt; 939&lt;span id="cb1-2"&gt;&lt;a href="#cb1-2"&gt;&lt;/a&gt;&lt;span class="kw"&gt;for&lt;/span&gt; &lt;span class="ex"&gt;f&lt;/span&gt; in &lt;span class="va"&gt;$posts&lt;/span&gt;&lt;span class="kw"&gt;;&lt;/span&gt; &lt;span class="kw"&gt;do&lt;/span&gt;&lt;/span&gt;
908&lt;span id="cb1-3"&gt;&lt;a href="#cb1-3" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="va"&gt;file=&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;./posts/&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;$f&lt;/span&gt; &lt;span class="co"&gt;# `ls` mangled our file paths&lt;/span&gt;&lt;/span&gt; 940&lt;span id="cb1-3"&gt;&lt;a href="#cb1-3"&gt;&lt;/a&gt; &lt;span class="va"&gt;file=&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;./posts/&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;$f&lt;/span&gt; &lt;span class="co"&gt;# `ls` mangled our file paths&lt;/span&gt;&lt;/span&gt;
909&lt;span id="cb1-4"&gt;&lt;a href="#cb1-4" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="bu"&gt;echo&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;generating post &lt;/span&gt;&lt;span class="va"&gt;$file&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;/span&gt; 941&lt;span id="cb1-4"&gt;&lt;a href="#cb1-4"&gt;&lt;/a&gt; &lt;span class="bu"&gt;echo&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;generating post &lt;/span&gt;&lt;span class="va"&gt;$file&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;/span&gt;
910&lt;span id="cb1-5"&gt;&lt;a href="#cb1-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 942&lt;span id="cb1-5"&gt;&lt;a href="#cb1-5"&gt;&lt;/a&gt;&lt;/span&gt;
911&lt;span id="cb1-6"&gt;&lt;a href="#cb1-6" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="va"&gt;html=$(&lt;/span&gt;&lt;span class="ex"&gt;lowdown&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;$file&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;)&lt;/span&gt;&lt;/span&gt; 943&lt;span id="cb1-6"&gt;&lt;a href="#cb1-6"&gt;&lt;/a&gt; &lt;span class="va"&gt;html=$(&lt;/span&gt;&lt;span class="ex"&gt;lowdown&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;$file&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;)&lt;/span&gt;&lt;/span&gt;
912&lt;span id="cb1-7"&gt;&lt;a href="#cb1-7" aria-hidden="true"&gt;&lt;/a&gt; &lt;span class="bu"&gt;echo&lt;/span&gt; -e &lt;span class="st"&gt;&amp;quot;html&amp;quot;&lt;/span&gt; &lt;span class="op"&gt;&amp;gt;&amp;gt;&lt;/span&gt; docs/index.html&lt;/span&gt; 944&lt;span id="cb1-7"&gt;&lt;a href="#cb1-7"&gt;&lt;/a&gt; &lt;span class="bu"&gt;echo&lt;/span&gt; -e &lt;span class="st"&gt;&amp;quot;html&amp;quot;&lt;/span&gt; &lt;span class="op"&gt;&amp;gt;&amp;gt;&lt;/span&gt; docs/index.html&lt;/span&gt;
913&lt;span id="cb1-8"&gt;&lt;a href="#cb1-8" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="kw"&gt;done&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 945&lt;span id="cb1-8"&gt;&lt;a href="#cb1-8"&gt;&lt;/a&gt;&lt;span class="kw"&gt;done&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
914&lt;h3 id="assets"&gt;Assets&lt;/h3&gt; 946&lt;h3 id="assets"&gt;Assets&lt;/h3&gt;
915&lt;p&gt;Most static site generators recommend dropping image assets into the site source itself. That does have it’s merits, but I prefer hosting images separately:&lt;/p&gt; 947&lt;p&gt;Most static site generators recommend dropping image assets into the site source itself. That does have it’s merits, but I prefer hosting images separately:&lt;/p&gt;
916&lt;div class="sourceCode" id="cb2"&gt;&lt;pre class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb2-1"&gt;&lt;a href="#cb2-1" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;# strip file extension&lt;/span&gt;&lt;/span&gt; 948&lt;div class="sourceCode" id="cb2"&gt;&lt;pre class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb2-1"&gt;&lt;a href="#cb2-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# strip file extension&lt;/span&gt;&lt;/span&gt;
917&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="va"&gt;ext=&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;${1##&lt;/span&gt;*.&lt;span class="va"&gt;}&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;/span&gt; 949&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2"&gt;&lt;/a&gt;&lt;span class="va"&gt;ext=&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;${1##&lt;/span&gt;*.&lt;span class="va"&gt;}&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;/span&gt;
918&lt;span id="cb2-3"&gt;&lt;a href="#cb2-3" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 950&lt;span id="cb2-3"&gt;&lt;a href="#cb2-3"&gt;&lt;/a&gt;&lt;/span&gt;
919&lt;span id="cb2-4"&gt;&lt;a href="#cb2-4" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;# generate a random file name&lt;/span&gt;&lt;/span&gt; 951&lt;span id="cb2-4"&gt;&lt;a href="#cb2-4"&gt;&lt;/a&gt;&lt;span class="co"&gt;# generate a random file name&lt;/span&gt;&lt;/span&gt;
920&lt;span id="cb2-5"&gt;&lt;a href="#cb2-5" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="va"&gt;id=$(&lt;/span&gt; &lt;span class="fu"&gt;cat&lt;/span&gt; /dev/urandom &lt;span class="kw"&gt;|&lt;/span&gt; &lt;span class="fu"&gt;tr&lt;/span&gt; -dc &lt;span class="st"&gt;&amp;#39;a-zA-Z0-9&amp;#39;&lt;/span&gt; &lt;span class="kw"&gt;|&lt;/span&gt; &lt;span class="ex"&gt;fold&lt;/span&gt; -w 2 &lt;span class="kw"&gt;|&lt;/span&gt; &lt;span class="fu"&gt;head&lt;/span&gt; -n 1 &lt;span class="va"&gt;)&lt;/span&gt;&lt;/span&gt; 952&lt;span id="cb2-5"&gt;&lt;a href="#cb2-5"&gt;&lt;/a&gt;&lt;span class="va"&gt;id=$(&lt;/span&gt; &lt;span class="fu"&gt;cat&lt;/span&gt; /dev/urandom &lt;span class="kw"&gt;|&lt;/span&gt; &lt;span class="fu"&gt;tr&lt;/span&gt; -dc &lt;span class="st"&gt;&amp;#39;a-zA-Z0-9&amp;#39;&lt;/span&gt; &lt;span class="kw"&gt;|&lt;/span&gt; &lt;span class="ex"&gt;fold&lt;/span&gt; -w 2 &lt;span class="kw"&gt;|&lt;/span&gt; &lt;span class="fu"&gt;head&lt;/span&gt; -n 1 &lt;span class="va"&gt;)&lt;/span&gt;&lt;/span&gt;
921&lt;span id="cb2-6"&gt;&lt;a href="#cb2-6" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="va"&gt;id=&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;$id&lt;/span&gt;&lt;span class="st"&gt;.&lt;/span&gt;&lt;span class="va"&gt;$ext&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;/span&gt; 953&lt;span id="cb2-6"&gt;&lt;a href="#cb2-6"&gt;&lt;/a&gt;&lt;span class="va"&gt;id=&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;$id&lt;/span&gt;&lt;span class="st"&gt;.&lt;/span&gt;&lt;span class="va"&gt;$ext&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;/span&gt;
922&lt;span id="cb2-7"&gt;&lt;a href="#cb2-7" aria-hidden="true"&gt;&lt;/a&gt;&lt;/span&gt; 954&lt;span id="cb2-7"&gt;&lt;a href="#cb2-7"&gt;&lt;/a&gt;&lt;/span&gt;
923&lt;span id="cb2-8"&gt;&lt;a href="#cb2-8" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="co"&gt;# copy to my file host&lt;/span&gt;&lt;/span&gt; 955&lt;span id="cb2-8"&gt;&lt;a href="#cb2-8"&gt;&lt;/a&gt;&lt;span class="co"&gt;# copy to my file host&lt;/span&gt;&lt;/span&gt;
924&lt;span id="cb2-9"&gt;&lt;a href="#cb2-9" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="fu"&gt;scp&lt;/span&gt; -P 443 &lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;$1&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt; emerald:files/&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;$id&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt; &lt;/span&gt; 956&lt;span id="cb2-9"&gt;&lt;a href="#cb2-9"&gt;&lt;/a&gt;&lt;span class="fu"&gt;scp&lt;/span&gt; -P 443 &lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;$1&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt; emerald:files/&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;$id&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt; &lt;/span&gt;
925&lt;span id="cb2-10"&gt;&lt;a href="#cb2-10" aria-hidden="true"&gt;&lt;/a&gt;&lt;span class="bu"&gt;echo&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;https://u.peppe.rs/&lt;/span&gt;&lt;span class="va"&gt;$id&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt; 957&lt;span id="cb2-10"&gt;&lt;a href="#cb2-10"&gt;&lt;/a&gt;&lt;span class="bu"&gt;echo&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;https://u.peppe.rs/&lt;/span&gt;&lt;span class="va"&gt;$id&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
926&lt;h3 id="templating"&gt;Templating&lt;/h3&gt; 958&lt;h3 id="templating"&gt;Templating&lt;/h3&gt;
927&lt;p&gt;&lt;a href="https://github.com/NerdyPepper/site/blob/master/generate.sh"&gt;&lt;code&gt;generate.sh&lt;/code&gt;&lt;/a&gt; brings the above bits and pieces together (with some extra cruft to avoid javascript). It uses &lt;code&gt;sed&lt;/code&gt; to produce nice titles from the file names (removes underscores, title-case), and &lt;code&gt;date(1)&lt;/code&gt; to add the date to each post listing!&lt;/p&gt;</description> 959&lt;p&gt;&lt;a href="https://github.com/NerdyPepper/site/blob/master/generate.sh"&gt;&lt;code&gt;generate.sh&lt;/code&gt;&lt;/a&gt; brings the above bits and pieces together (with some extra cruft to avoid javascript). It uses &lt;code&gt;sed&lt;/code&gt; to produce nice titles from the file names (removes underscores, title-case), and &lt;code&gt;date(1)&lt;/code&gt; to add the date to each post listing!&lt;/p&gt;</description>
928<link>https://peppe.rs/posts/static_sites_with_bash/</link> 960<link>https://peppe.rs/posts/static_sites_with_bash/</link>
@@ -968,7 +1000,7 @@ $ sudo ln -s /etc/sv/dhcpcd /var/service/
968$ sudo sv restart wpa_supplicant 1000$ sudo sv restart wpa_supplicant
969$ sudo sv restart dhcpcd&lt;/code&gt;&lt;/pre&gt;</description> 1001$ sudo sv restart dhcpcd&lt;/code&gt;&lt;/pre&gt;</description>
970<link>https://peppe.rs/posts/WPA_woes/</link> 1002<link>https://peppe.rs/posts/WPA_woes/</link>
971<pubDate>Sat, 12 Oct 2019 16:18:00 +0000</pubDate> 1003<pubDate>Sat, 12 Oct 2019 16:23:00 +0000</pubDate>
972<guid>https://peppe.rs/posts/WPA_woes/</guid> 1004<guid>https://peppe.rs/posts/WPA_woes/</guid>
973</item> 1005</item>
974<item> 1006<item>
@@ -980,7 +1012,7 @@ $ sudo sv restart dhcpcd&lt;/code&gt;&lt;/pre&gt;</description>
980&lt;p&gt;Upgrading to Pango v1.44 will break your GTK applications (if you use a &lt;code&gt;bdf&lt;/code&gt;/&lt;code&gt;pcf&lt;/code&gt; bitmap font). Harfbuzz &lt;em&gt;does&lt;/em&gt; support bitmap-only OpenType fonts, &lt;code&gt;otb&lt;/code&gt;s. Convert your existing fonts over to &lt;code&gt;otb&lt;/code&gt;s using &lt;a href="https://fontforge.github.io"&gt;FontForge&lt;/a&gt;. It is to be noted that applications such as &lt;code&gt;xterm&lt;/code&gt; and &lt;code&gt;rxvt&lt;/code&gt; use &lt;code&gt;xft&lt;/code&gt; (X FreeType) to render fonts, and will remain unaffected by the update.&lt;/p&gt; 1012&lt;p&gt;Upgrading to Pango v1.44 will break your GTK applications (if you use a &lt;code&gt;bdf&lt;/code&gt;/&lt;code&gt;pcf&lt;/code&gt; bitmap font). Harfbuzz &lt;em&gt;does&lt;/em&gt; support bitmap-only OpenType fonts, &lt;code&gt;otb&lt;/code&gt;s. Convert your existing fonts over to &lt;code&gt;otb&lt;/code&gt;s using &lt;a href="https://fontforge.github.io"&gt;FontForge&lt;/a&gt;. It is to be noted that applications such as &lt;code&gt;xterm&lt;/code&gt; and &lt;code&gt;rxvt&lt;/code&gt; use &lt;code&gt;xft&lt;/code&gt; (X FreeType) to render fonts, and will remain unaffected by the update.&lt;/p&gt;
981&lt;p&gt;Both &lt;a href="https://github.com/nerdypepper/scientifica"&gt;scientifica&lt;/a&gt; and &lt;a href="https://github.com/nerdypepper/curie"&gt;curie&lt;/a&gt; will soon ship with bitmap-only OpenType font formats.&lt;/p&gt;</description> 1013&lt;p&gt;Both &lt;a href="https://github.com/nerdypepper/scientifica"&gt;scientifica&lt;/a&gt; and &lt;a href="https://github.com/nerdypepper/curie"&gt;curie&lt;/a&gt; will soon ship with bitmap-only OpenType font formats.&lt;/p&gt;</description>
982<link>https://peppe.rs/posts/bye_bye_BDFs/</link> 1014<link>https://peppe.rs/posts/bye_bye_BDFs/</link>
983<pubDate>Wed, 07 Aug 2019 12:31:00 +0000</pubDate> 1015<pubDate>Wed, 07 Aug 2019 17:26:00 +0000</pubDate>
984<guid>https://peppe.rs/posts/bye_bye_BDFs/</guid> 1016<guid>https://peppe.rs/posts/bye_bye_BDFs/</guid>
985</item> 1017</item>
986<item> 1018<item>
@@ -991,7 +1023,7 @@ $ sudo sv restart dhcpcd&lt;/code&gt;&lt;/pre&gt;</description>
991&lt;p&gt;Onivim’s source code is available on &lt;a href="https://github.com/onivim/oni2"&gt;GitHub&lt;/a&gt;. They do mention that the source code trickles down to the &lt;a href="https://github.com/onivim/oni2-mit"&gt;oni2-mit&lt;/a&gt; repository, which (not yet) contains MIT-licensed code, &lt;strong&gt;18 months&lt;/strong&gt; after each commit to the original repository.&lt;/p&gt; 1023&lt;p&gt;Onivim’s source code is available on &lt;a href="https://github.com/onivim/oni2"&gt;GitHub&lt;/a&gt;. They do mention that the source code trickles down to the &lt;a href="https://github.com/onivim/oni2-mit"&gt;oni2-mit&lt;/a&gt; repository, which (not yet) contains MIT-licensed code, &lt;strong&gt;18 months&lt;/strong&gt; after each commit to the original repository.&lt;/p&gt;
992&lt;p&gt;Want to contribute to Onivim? Don’t. They make a profit out of your contributions. Currently, Onivim is priced at $19.99, ‘pre-alpha’ pricing which is 80% off the final price! If you are on the lookout for an editor, I would suggest using &lt;a href="https://vim.org"&gt;Vim&lt;/a&gt;, charity ware that actually works, and costs $100 lesser.&lt;/p&gt;</description> 1024&lt;p&gt;Want to contribute to Onivim? Don’t. They make a profit out of your contributions. Currently, Onivim is priced at $19.99, ‘pre-alpha’ pricing which is 80% off the final price! If you are on the lookout for an editor, I would suggest using &lt;a href="https://vim.org"&gt;Vim&lt;/a&gt;, charity ware that actually works, and costs $100 lesser.&lt;/p&gt;</description>
993<link>https://peppe.rs/posts/onivim_sucks/</link> 1025<link>https://peppe.rs/posts/onivim_sucks/</link>
994<pubDate>Fri, 02 Aug 2019 12:31:00 +0000</pubDate> 1026<pubDate>Fri, 02 Aug 2019 16:32:00 +0000</pubDate>
995<guid>https://peppe.rs/posts/onivim_sucks/</guid> 1027<guid>https://peppe.rs/posts/onivim_sucks/</guid>
996</item> 1028</item>
997<item> 1029<item>
@@ -1031,7 +1063,7 @@ w | so %
1031New Post # output 1063New Post # output
1032Press ENTER or type command to continue&lt;/code&gt;&lt;/pre&gt;</description> 1064Press ENTER or type command to continue&lt;/code&gt;&lt;/pre&gt;</description>
1033<link>https://peppe.rs/posts/bash_harder_with_vim/</link> 1065<link>https://peppe.rs/posts/bash_harder_with_vim/</link>
1034<pubDate>Wed, 31 Jul 2019 06:30:00 +0000</pubDate> 1066<pubDate>Tue, 30 Jul 2019 18:30:00 +0000</pubDate>
1035<guid>https://peppe.rs/posts/bash_harder_with_vim/</guid> 1067<guid>https://peppe.rs/posts/bash_harder_with_vim/</guid>
1036</item> 1068</item>
1037<item> 1069<item>
@@ -1045,7 +1077,7 @@ s/\s\+$//gc &amp;quot; find and (confirm) replace trailing blanks
1045winrestview(view) &amp;quot; restore our original view!&lt;/code&gt;&lt;/pre&gt; 1077winrestview(view) &amp;quot; restore our original view!&lt;/code&gt;&lt;/pre&gt;
1046&lt;p&gt;It might seem a little overkill in the above example, just use `` (double backticks) instead, but it comes in handy when you run your file through heavier filtering.&lt;/p&gt;</description> 1078&lt;p&gt;It might seem a little overkill in the above example, just use `` (double backticks) instead, but it comes in handy when you run your file through heavier filtering.&lt;/p&gt;</description>
1047<link>https://peppe.rs/posts/hold_position!/</link> 1079<link>https://peppe.rs/posts/hold_position!/</link>
1048<pubDate>Tue, 30 Jul 2019 12:31:00 +0000</pubDate> 1080<pubDate>Tue, 30 Jul 2019 14:45:00 +0000</pubDate>
1049<guid>https://peppe.rs/posts/hold_position!/</guid> 1081<guid>https://peppe.rs/posts/hold_position!/</guid>
1050</item> 1082</item>
1051<item> 1083<item>
@@ -1068,7 +1100,7 @@ nnoremap gb `[v`] &amp;quot; &amp;quot;a quick map to perform the above&lt;/c
1068]P &amp;quot; put the text before the cursor (P) and adjust indent to current line&lt;/code&gt;&lt;/pre&gt;&lt;/li&gt; 1100]P &amp;quot; put the text before the cursor (P) and adjust indent to current line&lt;/code&gt;&lt;/pre&gt;&lt;/li&gt;
1069&lt;/ol&gt;</description> 1101&lt;/ol&gt;</description>
1070<link>https://peppe.rs/posts/get_better_at_yanking_and_putting_in_vim/</link> 1102<link>https://peppe.rs/posts/get_better_at_yanking_and_putting_in_vim/</link>
1071<pubDate>Mon, 29 Jul 2019 12:31:00 +0000</pubDate> 1103<pubDate>Tue, 30 Jul 2019 08:43:00 +0000</pubDate>
1072<guid>https://peppe.rs/posts/get_better_at_yanking_and_putting_in_vim/</guid> 1104<guid>https://peppe.rs/posts/get_better_at_yanking_and_putting_in_vim/</guid>
1073</item> 1105</item>
1074 1106
diff --git a/docs/posts/auto-currying_rust_functions/index.html b/docs/posts/auto-currying_rust_functions/index.html
index 62f92bc..99cb9af 100644
--- a/docs/posts/auto-currying_rust_functions/index.html
+++ b/docs/posts/auto-currying_rust_functions/index.html
@@ -94,17 +94,17 @@ h(x)(y)(z) = g(y)(z) = k(z) = v</code></pre>
94<p>We will be using Attribute macros to convert a Rust function into a curried Rust function, which we should be able to call via: <code>function(arg1)(arg2)</code>.</p> 94<p>We will be using Attribute macros to convert a Rust function into a curried Rust function, which we should be able to call via: <code>function(arg1)(arg2)</code>.</p>
95<h3 id="definitions">Definitions</h3> 95<h3 id="definitions">Definitions</h3>
96<p>Being respectable programmers, we define the input to and the output from our proc-macro. Here’s a good non-trivial function to start out with:</p> 96<p>Being respectable programmers, we define the input to and the output from our proc-macro. Here’s a good non-trivial function to start out with:</p>
97<div class="sourceCode" id="cb4"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true"></a><span class="kw">fn</span> add(x<span class="op">:</span> <span class="dt">u32</span><span class="op">,</span> y<span class="op">:</span> <span class="dt">u32</span><span class="op">,</span> z<span class="op">:</span> <span class="dt">u32</span>) <span class="op">-&gt;</span> <span class="dt">u32</span> <span class="op">{</span></span> 97<div class="sourceCode" id="cb4"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb4-1"><a href="#cb4-1"></a><span class="kw">fn</span> add(x: <span class="dt">u32</span>, y: <span class="dt">u32</span>, z: <span class="dt">u32</span>) -&gt; <span class="dt">u32</span> <span class="op">{</span></span>
98<span id="cb4-2"><a href="#cb4-2" aria-hidden="true"></a> <span class="kw">return</span> x <span class="op">+</span> y <span class="op">+</span> z<span class="op">;</span></span> 98<span id="cb4-2"><a href="#cb4-2"></a> <span class="kw">return</span> x + y + z;</span>
99<span id="cb4-3"><a href="#cb4-3" aria-hidden="true"></a><span class="op">}</span></span></code></pre></div> 99<span id="cb4-3"><a href="#cb4-3"></a><span class="op">}</span></span></code></pre></div>
100<p>Hmm, what would our output look like? What should our proc-macro generate ideally? Well, if we understood currying correctly, we should accept an argument and return a function that accepts an argument and returns … you get the point. Something like this should do:</p> 100<p>Hmm, what would our output look like? What should our proc-macro generate ideally? Well, if we understood currying correctly, we should accept an argument and return a function that accepts an argument and returns … you get the point. Something like this should do:</p>
101<div class="sourceCode" id="cb5"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb5-1"><a href="#cb5-1" aria-hidden="true"></a><span class="kw">fn</span> add_curried1(x<span class="op">:</span> <span class="dt">u32</span>) <span class="op">-&gt;</span> <span class="op">?</span> <span class="op">{</span></span> 101<div class="sourceCode" id="cb5"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb5-1"><a href="#cb5-1"></a><span class="kw">fn</span> add_curried1(x: <span class="dt">u32</span>) -&gt; ? <span class="op">{</span></span>
102<span id="cb5-2"><a href="#cb5-2" aria-hidden="true"></a> <span class="kw">return</span> <span class="kw">fn</span> add_curried2 (y<span class="op">:</span> <span class="dt">u32</span>) <span class="op">-&gt;</span> <span class="op">?</span> <span class="op">{</span></span> 102<span id="cb5-2"><a href="#cb5-2"></a> <span class="kw">return</span> <span class="kw">fn</span> add_curried2 (y: <span class="dt">u32</span>) -&gt; ? <span class="op">{</span></span>
103<span id="cb5-3"><a href="#cb5-3" aria-hidden="true"></a> <span class="kw">return</span> <span class="kw">fn</span> add_curried3 (z<span class="op">:</span> <span class="dt">u32</span>) <span class="op">-&gt;</span> <span class="dt">u32</span> <span class="op">{</span></span> 103<span id="cb5-3"><a href="#cb5-3"></a> <span class="kw">return</span> <span class="kw">fn</span> add_curried3 (z: <span class="dt">u32</span>) -&gt; <span class="dt">u32</span> <span class="op">{</span></span>
104<span id="cb5-4"><a href="#cb5-4" aria-hidden="true"></a> <span class="kw">return</span> x <span class="op">+</span> y <span class="op">+</span> z<span class="op">;</span></span> 104<span id="cb5-4"><a href="#cb5-4"></a> <span class="kw">return</span> x + y + z;</span>
105<span id="cb5-5"><a href="#cb5-5" aria-hidden="true"></a> <span class="op">}</span></span> 105<span id="cb5-5"><a href="#cb5-5"></a> <span class="op">}</span></span>
106<span id="cb5-6"><a href="#cb5-6" aria-hidden="true"></a> <span class="op">}</span></span> 106<span id="cb5-6"><a href="#cb5-6"></a> <span class="op">}</span></span>
107<span id="cb5-7"><a href="#cb5-7" aria-hidden="true"></a><span class="op">}</span></span></code></pre></div> 107<span id="cb5-7"><a href="#cb5-7"></a><span class="op">}</span></span></code></pre></div>
108<p>A couple of things to note:</p> 108<p>A couple of things to note:</p>
109<p><strong>Return types</strong><br /> 109<p><strong>Return types</strong><br />
110We have placed <code>?</code>s in place of return types. Let’s try to fix that. <code>add_curried3</code> returns the ‘value’, so <code>u32</code> is accurate. <code>add_curried2</code> returns <code>add_curried3</code>. What is the type of <code>add_curried3</code>? It is a function that takes in a <code>u32</code> and returns a <code>u32</code>. So a <code>fn(u32) -&gt; u32</code> will do right? No, I’ll explain why in the next point, but for now, we will make use of the <code>Fn</code> trait, our return type is <code>impl Fn(u32) -&gt; u32</code>. This basically tells the compiler that we will be returning something function-like, a.k.a, behaves like a <code>Fn</code>. Cool!</p> 110We have placed <code>?</code>s in place of return types. Let’s try to fix that. <code>add_curried3</code> returns the ‘value’, so <code>u32</code> is accurate. <code>add_curried2</code> returns <code>add_curried3</code>. What is the type of <code>add_curried3</code>? It is a function that takes in a <code>u32</code> and returns a <code>u32</code>. So a <code>fn(u32) -&gt; u32</code> will do right? No, I’ll explain why in the next point, but for now, we will make use of the <code>Fn</code> trait, our return type is <code>impl Fn(u32) -&gt; u32</code>. This basically tells the compiler that we will be returning something function-like, a.k.a, behaves like a <code>Fn</code>. Cool!</p>
@@ -117,9 +117,9 @@ We have placed <code>?</code>s in place of return types. Let’s try to fix that
117A function cannot access it’s environment. Our solution will not work. <code>add_curried3</code> attempts to access <code>x</code>, which is not allowed! A closure<a href="#fn1" class="footnote-ref" id="fnref1" role="doc-noteref"><sup>1</sup></a> however, can. If we are returning a closure, our return type must be <code>impl Fn</code>, and not <code>fn</code>. The difference between the <code>Fn</code> trait and function pointers is beyond the scope of this post.</p> 117A function cannot access it’s environment. Our solution will not work. <code>add_curried3</code> attempts to access <code>x</code>, which is not allowed! A closure<a href="#fn1" class="footnote-ref" id="fnref1" role="doc-noteref"><sup>1</sup></a> however, can. If we are returning a closure, our return type must be <code>impl Fn</code>, and not <code>fn</code>. The difference between the <code>Fn</code> trait and function pointers is beyond the scope of this post.</p>
118<h3 id="refinement">Refinement</h3> 118<h3 id="refinement">Refinement</h3>
119<p>Armed with knowledge, we refine our expected output, this time, employing closures:</p> 119<p>Armed with knowledge, we refine our expected output, this time, employing closures:</p>
120<div class="sourceCode" id="cb8"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb8-1"><a href="#cb8-1" aria-hidden="true"></a><span class="kw">fn</span> add(x<span class="op">:</span> <span class="dt">u32</span>) <span class="op">-&gt;</span> <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) <span class="op">-&gt;</span> <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) <span class="op">-&gt;</span> <span class="dt">u32</span> <span class="op">{</span></span> 120<div class="sourceCode" id="cb8"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb8-1"><a href="#cb8-1"></a><span class="kw">fn</span> add(x: <span class="dt">u32</span>) -&gt; <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) -&gt; <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) -&gt; <span class="dt">u32</span> <span class="op">{</span></span>
121<span id="cb8-2"><a href="#cb8-2" aria-hidden="true"></a> <span class="kw">return</span> <span class="kw">move</span> <span class="op">|</span>y<span class="op">|</span> <span class="kw">move</span> <span class="op">|</span>z<span class="op">|</span> x <span class="op">+</span> y <span class="op">+</span> z<span class="op">;</span></span> 121<span id="cb8-2"><a href="#cb8-2"></a> <span class="kw">return</span> <span class="kw">move</span> |y| <span class="kw">move</span> |z| x + y + z;</span>
122<span id="cb8-3"><a href="#cb8-3" aria-hidden="true"></a><span class="op">}</span></span></code></pre></div> 122<span id="cb8-3"><a href="#cb8-3"></a><span class="op">}</span></span></code></pre></div>
123<p>Alas, that does not compile either! It errors out with the following message:</p> 123<p>Alas, that does not compile either! It errors out with the following message:</p>
124<pre><code>error[E0562]: `impl Trait` not allowed outside of function 124<pre><code>error[E0562]: `impl Trait` not allowed outside of function
125and inherent method return types 125and inherent method return types
@@ -130,15 +130,15 @@ and inherent method return types
130</code></pre> 130</code></pre>
131<p>You are allowed to return an <code>impl Fn</code> only inside a function. We are currently returning it from another return! Or at least, that was the most I could make out of the error message.</p> 131<p>You are allowed to return an <code>impl Fn</code> only inside a function. We are currently returning it from another return! Or at least, that was the most I could make out of the error message.</p>
132<p>We are going to have to cheat a bit to fix this issue; with type aliases and a convenient nightly feature <a href="#fn2" class="footnote-ref" id="fnref2" role="doc-noteref"><sup>2</sup></a>:</p> 132<p>We are going to have to cheat a bit to fix this issue; with type aliases and a convenient nightly feature <a href="#fn2" class="footnote-ref" id="fnref2" role="doc-noteref"><sup>2</sup></a>:</p>
133<div class="sourceCode" id="cb10"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb10-1"><a href="#cb10-1" aria-hidden="true"></a><span class="at">#![</span>feature<span class="at">(</span>type_alias_impl_trait<span class="at">)]</span> <span class="co">// allows us to use `impl Fn` in type aliases!</span></span> 133<div class="sourceCode" id="cb10"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb10-1"><a href="#cb10-1"></a><span class="at">#![</span>feature<span class="at">(</span>type_alias_impl_trait<span class="at">)]</span> <span class="co">// allows us to use `impl Fn` in type aliases!</span></span>
134<span id="cb10-2"><a href="#cb10-2" aria-hidden="true"></a></span> 134<span id="cb10-2"><a href="#cb10-2"></a></span>
135<span id="cb10-3"><a href="#cb10-3" aria-hidden="true"></a><span class="kw">type</span> T0 <span class="op">=</span> <span class="dt">u32</span><span class="op">;</span> <span class="co">// the return value when zero args are to be applied</span></span> 135<span id="cb10-3"><a href="#cb10-3"></a><span class="kw">type</span> T0 = <span class="dt">u32</span>; <span class="co">// the return value when zero args are to be applied</span></span>
136<span id="cb10-4"><a href="#cb10-4" aria-hidden="true"></a><span class="kw">type</span> T1 <span class="op">=</span> <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) <span class="op">-&gt;</span> T0<span class="op">;</span> <span class="co">// the return value when one arg is to be applied</span></span> 136<span id="cb10-4"><a href="#cb10-4"></a><span class="kw">type</span> T1 = <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) -&gt; T0; <span class="co">// the return value when one arg is to be applied</span></span>
137<span id="cb10-5"><a href="#cb10-5" aria-hidden="true"></a><span class="kw">type</span> T2 <span class="op">=</span> <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) <span class="op">-&gt;</span> T1<span class="op">;</span> <span class="co">// the return value when two args are to be applied</span></span> 137<span id="cb10-5"><a href="#cb10-5"></a><span class="kw">type</span> T2 = <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) -&gt; T1; <span class="co">// the return value when two args are to be applied</span></span>
138<span id="cb10-6"><a href="#cb10-6" aria-hidden="true"></a></span> 138<span id="cb10-6"><a href="#cb10-6"></a></span>
139<span id="cb10-7"><a href="#cb10-7" aria-hidden="true"></a><span class="kw">fn</span> add(x<span class="op">:</span> <span class="dt">u32</span>) <span class="op">-&gt;</span> T2 <span class="op">{</span></span> 139<span id="cb10-7"><a href="#cb10-7"></a><span class="kw">fn</span> add(x: <span class="dt">u32</span>) -&gt; T2 <span class="op">{</span></span>
140<span id="cb10-8"><a href="#cb10-8" aria-hidden="true"></a> <span class="kw">return</span> <span class="kw">move</span> <span class="op">|</span>y<span class="op">|</span> <span class="kw">move</span> <span class="op">|</span>z<span class="op">|</span> x <span class="op">+</span> y <span class="op">+</span> z<span class="op">;</span></span> 140<span id="cb10-8"><a href="#cb10-8"></a> <span class="kw">return</span> <span class="kw">move</span> |y| <span class="kw">move</span> |z| x + y + z;</span>
141<span id="cb10-9"><a href="#cb10-9" aria-hidden="true"></a><span class="op">}</span></span></code></pre></div> 141<span id="cb10-9"><a href="#cb10-9"></a><span class="op">}</span></span></code></pre></div>
142<p>Drop that into a cargo project, call <code>add(4)(5)(6)</code>, cross your fingers, and run <code>cargo +nightly run</code>. You should see a 15 unless you forgot to print it!</p> 142<p>Drop that into a cargo project, call <code>add(4)(5)(6)</code>, cross your fingers, and run <code>cargo +nightly run</code>. You should see a 15 unless you forgot to print it!</p>
143<h3 id="the-in-betweens">The In-Betweens</h3> 143<h3 id="the-in-betweens">The In-Betweens</h3>
144<p>Let us write the magical bits that take us from function to curried function.</p> 144<p>Let us write the magical bits that take us from function to curried function.</p>
@@ -172,19 +172,19 @@ proc-macro = true # this is important!</code></pre>
172<p>We will be using an external <code>proc-macro2</code> crate as well as an internal <code>proc-macro</code> crate. Not confusing at all!</p> 172<p>We will be using an external <code>proc-macro2</code> crate as well as an internal <code>proc-macro</code> crate. Not confusing at all!</p>
173<h4 id="the-attribute-macro">The attribute macro</h4> 173<h4 id="the-attribute-macro">The attribute macro</h4>
174<p>Drop this into <code>src/lib.rs</code>, to get the ball rolling.</p> 174<p>Drop this into <code>src/lib.rs</code>, to get the ball rolling.</p>
175<div class="sourceCode" id="cb13"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb13-1"><a href="#cb13-1" aria-hidden="true"></a><span class="co">// src/lib.rs</span></span> 175<div class="sourceCode" id="cb13"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb13-1"><a href="#cb13-1"></a><span class="co">// src/lib.rs</span></span>
176<span id="cb13-2"><a href="#cb13-2" aria-hidden="true"></a></span> 176<span id="cb13-2"><a href="#cb13-2"></a></span>
177<span id="cb13-3"><a href="#cb13-3" aria-hidden="true"></a><span class="kw">use</span> <span class="pp">proc_macro::</span>TokenStream<span class="op">;</span> <span class="co">// 1</span></span> 177<span id="cb13-3"><a href="#cb13-3"></a><span class="kw">use</span> <span class="pp">proc_macro::</span>TokenStream; <span class="co">// 1</span></span>
178<span id="cb13-4"><a href="#cb13-4" aria-hidden="true"></a><span class="kw">use</span> <span class="pp">quote::</span>quote<span class="op">;</span></span> 178<span id="cb13-4"><a href="#cb13-4"></a><span class="kw">use</span> <span class="pp">quote::</span>quote;</span>
179<span id="cb13-5"><a href="#cb13-5" aria-hidden="true"></a><span class="kw">use</span> <span class="pp">syn::</span><span class="op">{</span>parse_macro_input<span class="op">,</span> ItemFn<span class="op">};</span></span> 179<span id="cb13-5"><a href="#cb13-5"></a><span class="kw">use</span> <span class="pp">syn::</span><span class="op">{</span>parse_macro_input, ItemFn<span class="op">}</span>;</span>
180<span id="cb13-6"><a href="#cb13-6" aria-hidden="true"></a></span> 180<span id="cb13-6"><a href="#cb13-6"></a></span>
181<span id="cb13-7"><a href="#cb13-7" aria-hidden="true"></a><span class="at">#[</span>proc_macro_attribute<span class="at">]</span> <span class="co">// 2</span></span> 181<span id="cb13-7"><a href="#cb13-7"></a><span class="at">#[</span>proc_macro_attribute<span class="at">]</span> <span class="co">// 2</span></span>
182<span id="cb13-8"><a href="#cb13-8" aria-hidden="true"></a><span class="kw">pub</span> <span class="kw">fn</span> curry(_attr<span class="op">:</span> TokenStream<span class="op">,</span> item<span class="op">:</span> TokenStream) <span class="op">-&gt;</span> TokenStream <span class="op">{</span></span> 182<span id="cb13-8"><a href="#cb13-8"></a><span class="kw">pub</span> <span class="kw">fn</span> curry(_attr: TokenStream, item: TokenStream) -&gt; TokenStream <span class="op">{</span></span>
183<span id="cb13-9"><a href="#cb13-9" aria-hidden="true"></a> <span class="kw">let</span> parsed <span class="op">=</span> <span class="pp">parse_macro_input!</span>(item <span class="kw">as</span> ItemFn)<span class="op">;</span> <span class="co">// 3</span></span> 183<span id="cb13-9"><a href="#cb13-9"></a> <span class="kw">let</span> parsed = <span class="pp">parse_macro_input!</span>(item <span class="kw">as</span> ItemFn); <span class="co">// 3</span></span>
184<span id="cb13-10"><a href="#cb13-10" aria-hidden="true"></a> generate_curry(parsed)<span class="op">.</span>into() <span class="co">// 4</span></span> 184<span id="cb13-10"><a href="#cb13-10"></a> generate_curry(parsed).into() <span class="co">// 4</span></span>
185<span id="cb13-11"><a href="#cb13-11" aria-hidden="true"></a><span class="op">}</span></span> 185<span id="cb13-11"><a href="#cb13-11"></a><span class="op">}</span></span>
186<span id="cb13-12"><a href="#cb13-12" aria-hidden="true"></a></span> 186<span id="cb13-12"><a href="#cb13-12"></a></span>
187<span id="cb13-13"><a href="#cb13-13" aria-hidden="true"></a><span class="kw">fn</span> generate_curry(parsed<span class="op">:</span> ItemFn) <span class="op">-&gt;</span> <span class="pp">proc_macro2::</span>TokenStream <span class="op">{}</span></span></code></pre></div> 187<span id="cb13-13"><a href="#cb13-13"></a><span class="kw">fn</span> generate_curry(parsed: ItemFn) -&gt; <span class="pp">proc_macro2::</span>TokenStream <span class="op">{}</span></span></code></pre></div>
188<p><strong>1. Imports</strong></p> 188<p><strong>1. Imports</strong></p>
189<p>A <code>Tokenstream</code> holds (hopefully valid) Rust code, this is the type of our input and output. Note that we are importing this type from <code>proc_macro</code> and not <code>proc_macro2</code>.</p> 189<p>A <code>Tokenstream</code> holds (hopefully valid) Rust code, this is the type of our input and output. Note that we are importing this type from <code>proc_macro</code> and not <code>proc_macro2</code>.</p>
190<p><code>quote!</code> from the <code>quote</code> crate is a macro that allows us to quickly produce <code>TokenStream</code>s. Much like the LISP <code>quote</code> procedure, you can use the <code>quote!</code> macro for symbolic transformations.</p> 190<p><code>quote!</code> from the <code>quote</code> crate is a macro that allows us to quickly produce <code>TokenStream</code>s. Much like the LISP <code>quote</code> procedure, you can use the <code>quote!</code> macro for symbolic transformations.</p>
@@ -196,16 +196,16 @@ proc-macro = true # this is important!</code></pre>
196<p><strong>4. Returning <code>TokenStream</code>s </strong></p> 196<p><strong>4. Returning <code>TokenStream</code>s </strong></p>
197<p>We haven’t filled in <code>generate_curry</code> yet, but we can see that it returns a <code>proc_macro2::TokenStream</code> and not a <code>proc_macro::TokenStream</code>, so drop a <code>.into()</code> to convert it.</p> 197<p>We haven’t filled in <code>generate_curry</code> yet, but we can see that it returns a <code>proc_macro2::TokenStream</code> and not a <code>proc_macro::TokenStream</code>, so drop a <code>.into()</code> to convert it.</p>
198<p>Lets move on, and fill in <code>generate_curry</code>, I would suggest keeping the documentation for <a href="https://docs.rs/syn/1.0.19/syn/struct.ItemFn.html"><code>syn::ItemFn</code></a> and <a href="https://docs.rs/syn/1.0.19/syn/struct.Signature.html"><code>syn::Signature</code></a> open.</p> 198<p>Lets move on, and fill in <code>generate_curry</code>, I would suggest keeping the documentation for <a href="https://docs.rs/syn/1.0.19/syn/struct.ItemFn.html"><code>syn::ItemFn</code></a> and <a href="https://docs.rs/syn/1.0.19/syn/struct.Signature.html"><code>syn::Signature</code></a> open.</p>
199<div class="sourceCode" id="cb14"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb14-1"><a href="#cb14-1" aria-hidden="true"></a><span class="co">// src/lib.rs</span></span> 199<div class="sourceCode" id="cb14"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb14-1"><a href="#cb14-1"></a><span class="co">// src/lib.rs</span></span>
200<span id="cb14-2"><a href="#cb14-2" aria-hidden="true"></a></span> 200<span id="cb14-2"><a href="#cb14-2"></a></span>
201<span id="cb14-3"><a href="#cb14-3" aria-hidden="true"></a><span class="kw">fn</span> generate_curry(parsed<span class="op">:</span> ItemFn) <span class="op">-&gt;</span> <span class="pp">proc_macro2::</span>TokenStream <span class="op">{</span></span> 201<span id="cb14-3"><a href="#cb14-3"></a><span class="kw">fn</span> generate_curry(parsed: ItemFn) -&gt; <span class="pp">proc_macro2::</span>TokenStream <span class="op">{</span></span>
202<span id="cb14-4"><a href="#cb14-4" aria-hidden="true"></a> <span class="kw">let</span> fn_body <span class="op">=</span> parsed<span class="op">.</span>block<span class="op">;</span> <span class="co">// function body</span></span> 202<span id="cb14-4"><a href="#cb14-4"></a> <span class="kw">let</span> fn_body = parsed.block; <span class="co">// function body</span></span>
203<span id="cb14-5"><a href="#cb14-5" aria-hidden="true"></a> <span class="kw">let</span> sig <span class="op">=</span> parsed<span class="op">.</span>sig<span class="op">;</span> <span class="co">// function signature</span></span> 203<span id="cb14-5"><a href="#cb14-5"></a> <span class="kw">let</span> sig = parsed.sig; <span class="co">// function signature</span></span>
204<span id="cb14-6"><a href="#cb14-6" aria-hidden="true"></a> <span class="kw">let</span> vis <span class="op">=</span> parsed<span class="op">.</span>vis<span class="op">;</span> <span class="co">// visibility, pub or not</span></span> 204<span id="cb14-6"><a href="#cb14-6"></a> <span class="kw">let</span> vis = parsed.vis; <span class="co">// visibility, pub or not</span></span>
205<span id="cb14-7"><a href="#cb14-7" aria-hidden="true"></a> <span class="kw">let</span> fn_name <span class="op">=</span> sig<span class="op">.</span>ident<span class="op">;</span> <span class="co">// function name/identifier</span></span> 205<span id="cb14-7"><a href="#cb14-7"></a> <span class="kw">let</span> fn_name = sig.ident; <span class="co">// function name/identifier</span></span>
206<span id="cb14-8"><a href="#cb14-8" aria-hidden="true"></a> <span class="kw">let</span> fn_args <span class="op">=</span> sig<span class="op">.</span>inputs<span class="op">;</span> <span class="co">// comma separated args</span></span> 206<span id="cb14-8"><a href="#cb14-8"></a> <span class="kw">let</span> fn_args = sig.inputs; <span class="co">// comma separated args</span></span>
207<span id="cb14-9"><a href="#cb14-9" aria-hidden="true"></a> <span class="kw">let</span> fn_return_type <span class="op">=</span> sig<span class="op">.</span>output<span class="op">;</span> <span class="co">// return type</span></span> 207<span id="cb14-9"><a href="#cb14-9"></a> <span class="kw">let</span> fn_return_type = sig.output; <span class="co">// return type</span></span>
208<span id="cb14-10"><a href="#cb14-10" aria-hidden="true"></a><span class="op">}</span></span></code></pre></div> 208<span id="cb14-10"><a href="#cb14-10"></a><span class="op">}</span></span></code></pre></div>
209<p>We are simply extracting the bits of the function, we will be reusing the original function’s visibility and name. Take a look at what <code>syn::Signature</code> can tell us about a function:</p> 209<p>We are simply extracting the bits of the function, we will be reusing the original function’s visibility and name. Take a look at what <code>syn::Signature</code> can tell us about a function:</p>
210<pre><code> .-- syn::Ident (ident) 210<pre><code> .-- syn::Ident (ident)
211 / 211 /
@@ -217,220 +217,220 @@ syn::token::Fn --&#39; / \ (output)
217<p>Enough analysis, lets produce our first bit of Rust code.</p> 217<p>Enough analysis, lets produce our first bit of Rust code.</p>
218<h4 id="function-body">Function Body</h4> 218<h4 id="function-body">Function Body</h4>
219<p>Recall that the body of a curried <code>add</code> should look like this:</p> 219<p>Recall that the body of a curried <code>add</code> should look like this:</p>
220<div class="sourceCode" id="cb16"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb16-1"><a href="#cb16-1" aria-hidden="true"></a><span class="kw">return</span> <span class="kw">move</span> <span class="op">|</span>y<span class="op">|</span> <span class="kw">move</span> <span class="op">|</span>z<span class="op">|</span> x <span class="op">+</span> y <span class="op">+</span> z<span class="op">;</span></span></code></pre></div> 220<div class="sourceCode" id="cb16"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb16-1"><a href="#cb16-1"></a><span class="kw">return</span> <span class="kw">move</span> |y| <span class="kw">move</span> |z| x + y + z;</span></code></pre></div>
221<p>And in general:</p> 221<p>And in general:</p>
222<div class="sourceCode" id="cb17"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb17-1"><a href="#cb17-1" aria-hidden="true"></a><span class="kw">return</span> <span class="kw">move</span> <span class="op">|</span>arg2<span class="op">|</span> <span class="kw">move</span> <span class="op">|</span>arg3<span class="op">|</span> <span class="op">...</span> <span class="op">|</span>argN<span class="op">|</span> <span class="op">&lt;</span>function body here<span class="op">&gt;</span></span></code></pre></div> 222<div class="sourceCode" id="cb17"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb17-1"><a href="#cb17-1"></a><span class="kw">return</span> <span class="kw">move</span> |arg2| <span class="kw">move</span> |arg3| ... |argN| &lt;function body here&gt;</span></code></pre></div>
223<p>We already have the function’s body, provided by <code>fn_body</code>, in our <code>generate_curry</code> function. All that’s left to add is the <code>move |arg2| move |arg3| ...</code> stuff, for which we need to extract the argument identifiers (doc: <a href="https://docs.rs/syn/1.0.18/syn/punctuated/struct.Punctuated.html">Punctuated</a>, <a href="https://docs.rs/syn/1.0.18/syn/enum.FnArg.html">FnArg</a>, <a href="https://docs.rs/syn/1.0.18/syn/struct.PatType.html">PatType</a>):</p> 223<p>We already have the function’s body, provided by <code>fn_body</code>, in our <code>generate_curry</code> function. All that’s left to add is the <code>move |arg2| move |arg3| ...</code> stuff, for which we need to extract the argument identifiers (doc: <a href="https://docs.rs/syn/1.0.18/syn/punctuated/struct.Punctuated.html">Punctuated</a>, <a href="https://docs.rs/syn/1.0.18/syn/enum.FnArg.html">FnArg</a>, <a href="https://docs.rs/syn/1.0.18/syn/struct.PatType.html">PatType</a>):</p>
224<div class="sourceCode" id="cb18"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb18-1"><a href="#cb18-1" aria-hidden="true"></a><span class="co">// src/lib.rs</span></span> 224<div class="sourceCode" id="cb18"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb18-1"><a href="#cb18-1"></a><span class="co">// src/lib.rs</span></span>
225<span id="cb18-2"><a href="#cb18-2" aria-hidden="true"></a><span class="kw">use</span> <span class="pp">syn::punctuated::</span>Punctuated<span class="op">;</span></span> 225<span id="cb18-2"><a href="#cb18-2"></a><span class="kw">use</span> <span class="pp">syn::punctuated::</span>Punctuated;</span>
226<span id="cb18-3"><a href="#cb18-3" aria-hidden="true"></a><span class="kw">use</span> <span class="pp">syn::</span><span class="op">{</span>parse_macro_input<span class="op">,</span> FnArg<span class="op">,</span> Pat<span class="op">,</span> ItemFn<span class="op">,</span> Block<span class="op">};</span></span> 226<span id="cb18-3"><a href="#cb18-3"></a><span class="kw">use</span> <span class="pp">syn::</span><span class="op">{</span>parse_macro_input, FnArg, Pat, ItemFn, Block<span class="op">}</span>;</span>
227<span id="cb18-4"><a href="#cb18-4" aria-hidden="true"></a></span> 227<span id="cb18-4"><a href="#cb18-4"></a></span>
228<span id="cb18-5"><a href="#cb18-5" aria-hidden="true"></a><span class="kw">fn</span> extract_arg_idents(fn_args<span class="op">:</span> Punctuated<span class="op">&lt;</span>FnArg<span class="op">,</span> <span class="pp">syn::token::</span>Comma<span class="op">&gt;</span>) <span class="op">-&gt;</span> <span class="dt">Vec</span><span class="op">&lt;</span><span class="dt">Box</span><span class="op">&lt;</span>Pat<span class="op">&gt;&gt;</span> <span class="op">{</span> </span> 228<span id="cb18-5"><a href="#cb18-5"></a><span class="kw">fn</span> extract_arg_idents(fn_args: Punctuated&lt;FnArg, <span class="pp">syn::token::</span>Comma&gt;) -&gt; <span class="dt">Vec</span>&lt;<span class="dt">Box</span>&lt;Pat&gt;&gt; <span class="op">{</span> </span>
229<span id="cb18-6"><a href="#cb18-6" aria-hidden="true"></a> <span class="kw">return</span> fn_args<span class="op">.</span>into_iter()<span class="op">.</span>map(extract_arg_pat)<span class="op">.</span><span class="pp">collect::</span><span class="op">&lt;</span><span class="dt">Vec</span><span class="op">&lt;</span>_<span class="op">&gt;&gt;</span>()<span class="op">;</span></span> 229<span id="cb18-6"><a href="#cb18-6"></a> <span class="kw">return</span> fn_args.into_iter().map(extract_arg_pat).<span class="pp">collect::</span>&lt;<span class="dt">Vec</span>&lt;_&gt;&gt;();</span>
230<span id="cb18-7"><a href="#cb18-7" aria-hidden="true"></a><span class="op">}</span></span></code></pre></div> 230<span id="cb18-7"><a href="#cb18-7"></a><span class="op">}</span></span></code></pre></div>
231<p>Alright, so we are iterating over function args (<code>Punctuated</code> is a collection that you can iterate over) and mapping an <code>extract_arg_pat</code> to every item. What’s <code>extract_arg_pat</code>?</p> 231<p>Alright, so we are iterating over function args (<code>Punctuated</code> is a collection that you can iterate over) and mapping an <code>extract_arg_pat</code> to every item. What’s <code>extract_arg_pat</code>?</p>
232<div class="sourceCode" id="cb19"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb19-1"><a href="#cb19-1" aria-hidden="true"></a><span class="co">// src/lib.rs</span></span> 232<div class="sourceCode" id="cb19"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb19-1"><a href="#cb19-1"></a><span class="co">// src/lib.rs</span></span>
233<span id="cb19-2"><a href="#cb19-2" aria-hidden="true"></a></span> 233<span id="cb19-2"><a href="#cb19-2"></a></span>
234<span id="cb19-3"><a href="#cb19-3" aria-hidden="true"></a><span class="kw">fn</span> extract_arg_pat(a<span class="op">:</span> FnArg) <span class="op">-&gt;</span> <span class="dt">Box</span><span class="op">&lt;</span>Pat<span class="op">&gt;</span> <span class="op">{</span></span> 234<span id="cb19-3"><a href="#cb19-3"></a><span class="kw">fn</span> extract_arg_pat(a: FnArg) -&gt; <span class="dt">Box</span>&lt;Pat&gt; <span class="op">{</span></span>
235<span id="cb19-4"><a href="#cb19-4" aria-hidden="true"></a> <span class="kw">match</span> a <span class="op">{</span></span> 235<span id="cb19-4"><a href="#cb19-4"></a> <span class="kw">match</span> a <span class="op">{</span></span>
236<span id="cb19-5"><a href="#cb19-5" aria-hidden="true"></a> <span class="pp">FnArg::</span>Typed(p) <span class="op">=&gt;</span> p<span class="op">.</span>pat<span class="op">,</span></span> 236<span id="cb19-5"><a href="#cb19-5"></a> <span class="pp">FnArg::</span>Typed(p) =&gt; p.pat,</span>
237<span id="cb19-6"><a href="#cb19-6" aria-hidden="true"></a> _ <span class="op">=&gt;</span> <span class="pp">panic!</span>(<span class="st">&quot;Not supported on types with `self`!&quot;</span>)<span class="op">,</span></span> 237<span id="cb19-6"><a href="#cb19-6"></a> _ =&gt; <span class="pp">panic!</span>(<span class="st">&quot;Not supported on types with `self`!&quot;</span>),</span>
238<span id="cb19-7"><a href="#cb19-7" aria-hidden="true"></a> <span class="op">}</span></span> 238<span id="cb19-7"><a href="#cb19-7"></a> <span class="op">}</span></span>
239<span id="cb19-8"><a href="#cb19-8" aria-hidden="true"></a><span class="op">}</span></span></code></pre></div> 239<span id="cb19-8"><a href="#cb19-8"></a><span class="op">}</span></span></code></pre></div>
240<p><code>FnArg</code> is an enum type as you might have guessed. The <code>Typed</code> variant encompasses args that are written as <code>name: type</code> and the other variant, <code>Reciever</code> refers to <code>self</code> types. Ignore those for now, keep it simple.</p> 240<p><code>FnArg</code> is an enum type as you might have guessed. The <code>Typed</code> variant encompasses args that are written as <code>name: type</code> and the other variant, <code>Reciever</code> refers to <code>self</code> types. Ignore those for now, keep it simple.</p>
241<p>Every <code>FnArg::Typed</code> value contains a <code>pat</code>, which is in essence, the name of the argument. The type of the arg is accessible via <code>p.ty</code> (we will be using this later).</p> 241<p>Every <code>FnArg::Typed</code> value contains a <code>pat</code>, which is in essence, the name of the argument. The type of the arg is accessible via <code>p.ty</code> (we will be using this later).</p>
242<p>With that done, we should be able to write the codegen for the function body:</p> 242<p>With that done, we should be able to write the codegen for the function body:</p>
243<div class="sourceCode" id="cb20"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb20-1"><a href="#cb20-1" aria-hidden="true"></a><span class="co">// src/lib.rs</span></span> 243<div class="sourceCode" id="cb20"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb20-1"><a href="#cb20-1"></a><span class="co">// src/lib.rs</span></span>
244<span id="cb20-2"><a href="#cb20-2" aria-hidden="true"></a></span> 244<span id="cb20-2"><a href="#cb20-2"></a></span>
245<span id="cb20-3"><a href="#cb20-3" aria-hidden="true"></a><span class="kw">fn</span> generate_body(fn_args<span class="op">:</span> <span class="op">&amp;</span>[<span class="dt">Box</span><span class="op">&lt;</span>Pat<span class="op">&gt;</span>]<span class="op">,</span> body<span class="op">:</span> <span class="dt">Box</span><span class="op">&lt;</span>Block<span class="op">&gt;</span>) <span class="op">-&gt;</span> <span class="pp">proc_macro2::</span>TokenStream <span class="op">{</span></span> 245<span id="cb20-3"><a href="#cb20-3"></a><span class="kw">fn</span> generate_body(fn_args: &amp;<span class="op">[</span><span class="dt">Box</span>&lt;Pat&gt;<span class="op">]</span>, body: <span class="dt">Box</span>&lt;Block&gt;) -&gt; <span class="pp">proc_macro2::</span>TokenStream <span class="op">{</span></span>
246<span id="cb20-4"><a href="#cb20-4" aria-hidden="true"></a> <span class="pp">quote!</span> <span class="op">{</span></span> 246<span id="cb20-4"><a href="#cb20-4"></a> <span class="pp">quote!</span> <span class="op">{</span></span>
247<span id="cb20-5"><a href="#cb20-5" aria-hidden="true"></a> <span class="kw">return</span> #( <span class="kw">move</span> <span class="op">|</span>#fn_args<span class="op">|</span> )<span class="op">*</span> #body</span> 247<span id="cb20-5"><a href="#cb20-5"></a> <span class="kw">return</span> #( <span class="kw">move</span> |#fn_args| )* #body</span>
248<span id="cb20-6"><a href="#cb20-6" aria-hidden="true"></a> <span class="op">}</span></span> 248<span id="cb20-6"><a href="#cb20-6"></a> <span class="op">}</span></span>
249<span id="cb20-7"><a href="#cb20-7" aria-hidden="true"></a><span class="op">}</span></span></code></pre></div> 249<span id="cb20-7"><a href="#cb20-7"></a><span class="op">}</span></span></code></pre></div>
250<p>That is some scary looking syntax! Allow me to explain. The <code>quote!{ ... }</code> returns a <code>proc_macro2::TokenStream</code>, if we wrote <code>quote!{ let x = 1 + 2; }</code>, it wouldn’t create a new variable <code>x</code> with value 3, it would literally produce a stream of tokens with that expression.</p> 250<p>That is some scary looking syntax! Allow me to explain. The <code>quote!{ ... }</code> returns a <code>proc_macro2::TokenStream</code>, if we wrote <code>quote!{ let x = 1 + 2; }</code>, it wouldn’t create a new variable <code>x</code> with value 3, it would literally produce a stream of tokens with that expression.</p>
251<p>The <code>#</code> enables variable interpolation. <code>#body</code> will look for <code>body</code> in the current scope, take its value, and insert it in the returned <code>TokenStream</code>. Kinda like quasi quoting in LISPs, you have written one.</p> 251<p>The <code>#</code> enables variable interpolation. <code>#body</code> will look for <code>body</code> in the current scope, take its value, and insert it in the returned <code>TokenStream</code>. Kinda like quasi quoting in LISPs, you have written one.</p>
252<p>What about <code>#( move |#fn_args| )*</code>? That is repetition. <code>quote</code> iterates through <code>fn_args</code>, and drops a <code>move</code> behind each one, it then places pipes (<code>|</code>), around it.</p> 252<p>What about <code>#( move |#fn_args| )*</code>? That is repetition. <code>quote</code> iterates through <code>fn_args</code>, and drops a <code>move</code> behind each one, it then places pipes (<code>|</code>), around it.</p>
253<p>Let us test our first bit of codegen! Modify <code>generate_curry</code> like so:</p> 253<p>Let us test our first bit of codegen! Modify <code>generate_curry</code> like so:</p>
254<div class="sourceCode" id="cb21"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb21-1"><a href="#cb21-1" aria-hidden="true"></a><span class="co">// src/lib.rs</span></span> 254<div class="sourceCode" id="cb21"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb21-1"><a href="#cb21-1"></a><span class="co">// src/lib.rs</span></span>
255<span id="cb21-2"><a href="#cb21-2" aria-hidden="true"></a></span> 255<span id="cb21-2"><a href="#cb21-2"></a></span>
256<span id="cb21-3"><a href="#cb21-3" aria-hidden="true"></a> <span class="kw">fn</span> generate_curry(parsed<span class="op">:</span> ItemFn) <span class="op">-&gt;</span> TokenStream <span class="op">{</span></span> 256<span id="cb21-3"><a href="#cb21-3"></a> <span class="kw">fn</span> generate_curry(parsed: ItemFn) -&gt; TokenStream <span class="op">{</span></span>
257<span id="cb21-4"><a href="#cb21-4" aria-hidden="true"></a> <span class="kw">let</span> fn_body <span class="op">=</span> parsed<span class="op">.</span>block<span class="op">;</span></span> 257<span id="cb21-4"><a href="#cb21-4"></a> <span class="kw">let</span> fn_body = parsed.block;</span>
258<span id="cb21-5"><a href="#cb21-5" aria-hidden="true"></a> <span class="kw">let</span> sig <span class="op">=</span> parsed<span class="op">.</span>sig<span class="op">;</span></span> 258<span id="cb21-5"><a href="#cb21-5"></a> <span class="kw">let</span> sig = parsed.sig;</span>
259<span id="cb21-6"><a href="#cb21-6" aria-hidden="true"></a> <span class="kw">let</span> vis <span class="op">=</span> parsed<span class="op">.</span>vis<span class="op">;</span></span> 259<span id="cb21-6"><a href="#cb21-6"></a> <span class="kw">let</span> vis = parsed.vis;</span>
260<span id="cb21-7"><a href="#cb21-7" aria-hidden="true"></a> <span class="kw">let</span> fn_name <span class="op">=</span> sig<span class="op">.</span>ident<span class="op">;</span></span> 260<span id="cb21-7"><a href="#cb21-7"></a> <span class="kw">let</span> fn_name = sig.ident;</span>
261<span id="cb21-8"><a href="#cb21-8" aria-hidden="true"></a> <span class="kw">let</span> fn_args <span class="op">=</span> sig<span class="op">.</span>inputs<span class="op">;</span></span> 261<span id="cb21-8"><a href="#cb21-8"></a> <span class="kw">let</span> fn_args = sig.inputs;</span>
262<span id="cb21-9"><a href="#cb21-9" aria-hidden="true"></a> <span class="kw">let</span> fn_return_type <span class="op">=</span> sig<span class="op">.</span>output<span class="op">;</span></span> 262<span id="cb21-9"><a href="#cb21-9"></a> <span class="kw">let</span> fn_return_type = sig.output;</span>
263<span id="cb21-10"><a href="#cb21-10" aria-hidden="true"></a></span> 263<span id="cb21-10"><a href="#cb21-10"></a></span>
264<span id="cb21-11"><a href="#cb21-11" aria-hidden="true"></a><span class="op">+</span> <span class="kw">let</span> arg_idents <span class="op">=</span> extract_arg_idents(fn_args<span class="op">.</span>clone())<span class="op">;</span></span> 264<span id="cb21-11"><a href="#cb21-11"></a>+ <span class="kw">let</span> arg_idents = extract_arg_idents(fn_args.clone());</span>
265<span id="cb21-12"><a href="#cb21-12" aria-hidden="true"></a><span class="op">+</span> <span class="kw">let</span> first_ident <span class="op">=</span> <span class="op">&amp;</span>arg_idents<span class="op">.</span>first()<span class="op">.</span>unwrap()<span class="op">;</span></span> 265<span id="cb21-12"><a href="#cb21-12"></a>+ <span class="kw">let</span> first_ident = &amp;arg_idents.first().unwrap();</span>
266<span id="cb21-13"><a href="#cb21-13" aria-hidden="true"></a></span> 266<span id="cb21-13"><a href="#cb21-13"></a></span>
267<span id="cb21-14"><a href="#cb21-14" aria-hidden="true"></a><span class="op">+</span> <span class="co">// remember, our curried body starts with the second argument!</span></span> 267<span id="cb21-14"><a href="#cb21-14"></a>+ <span class="co">// remember, our curried body starts with the second argument!</span></span>
268<span id="cb21-15"><a href="#cb21-15" aria-hidden="true"></a><span class="op">+</span> <span class="kw">let</span> curried_body <span class="op">=</span> generate_body(<span class="op">&amp;</span>arg_idents[<span class="dv">1</span><span class="op">..</span>]<span class="op">,</span> fn_body<span class="op">.</span>clone())<span class="op">;</span></span> 268<span id="cb21-15"><a href="#cb21-15"></a>+ <span class="kw">let</span> curried_body = generate_body(&amp;arg_idents<span class="op">[</span><span class="dv">1</span>..<span class="op">]</span>, fn_body.clone());</span>
269<span id="cb21-16"><a href="#cb21-16" aria-hidden="true"></a><span class="op">+</span> <span class="pp">println!</span>(<span class="st">&quot;{}&quot;</span><span class="op">,</span> curried_body)<span class="op">;</span></span> 269<span id="cb21-16"><a href="#cb21-16"></a>+ <span class="pp">println!</span>(<span class="st">&quot;{}&quot;</span>, curried_body);</span>
270<span id="cb21-17"><a href="#cb21-17" aria-hidden="true"></a></span> 270<span id="cb21-17"><a href="#cb21-17"></a></span>
271<span id="cb21-18"><a href="#cb21-18" aria-hidden="true"></a> <span class="kw">return</span> <span class="pp">TokenStream::</span>new()<span class="op">;</span></span> 271<span id="cb21-18"><a href="#cb21-18"></a> <span class="kw">return</span> <span class="pp">TokenStream::</span>new();</span>
272<span id="cb21-19"><a href="#cb21-19" aria-hidden="true"></a> <span class="op">}</span></span></code></pre></div> 272<span id="cb21-19"><a href="#cb21-19"></a> <span class="op">}</span></span></code></pre></div>
273<p>Add a little test to <code>tests/</code>:</p> 273<p>Add a little test to <code>tests/</code>:</p>
274<div class="sourceCode" id="cb22"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb22-1"><a href="#cb22-1" aria-hidden="true"></a><span class="co">// tests/smoke.rs</span></span> 274<div class="sourceCode" id="cb22"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb22-1"><a href="#cb22-1"></a><span class="co">// tests/smoke.rs</span></span>
275<span id="cb22-2"><a href="#cb22-2" aria-hidden="true"></a></span> 275<span id="cb22-2"><a href="#cb22-2"></a></span>
276<span id="cb22-3"><a href="#cb22-3" aria-hidden="true"></a><span class="at">#[</span><span class="pp">currying::</span>curry<span class="at">]</span></span> 276<span id="cb22-3"><a href="#cb22-3"></a><span class="at">#[</span><span class="pp">currying::</span>curry<span class="at">]</span></span>
277<span id="cb22-4"><a href="#cb22-4" aria-hidden="true"></a><span class="kw">fn</span> add(x<span class="op">:</span> <span class="dt">u32</span><span class="op">,</span> y<span class="op">:</span> <span class="dt">u32</span><span class="op">,</span> z<span class="op">:</span> <span class="dt">u32</span>) <span class="op">-&gt;</span> <span class="dt">u32</span> <span class="op">{</span></span> 277<span id="cb22-4"><a href="#cb22-4"></a><span class="kw">fn</span> add(x: <span class="dt">u32</span>, y: <span class="dt">u32</span>, z: <span class="dt">u32</span>) -&gt; <span class="dt">u32</span> <span class="op">{</span></span>
278<span id="cb22-5"><a href="#cb22-5" aria-hidden="true"></a> x <span class="op">+</span> y <span class="op">+</span> z</span> 278<span id="cb22-5"><a href="#cb22-5"></a> x + y + z</span>
279<span id="cb22-6"><a href="#cb22-6" aria-hidden="true"></a><span class="op">}</span></span> 279<span id="cb22-6"><a href="#cb22-6"></a><span class="op">}</span></span>
280<span id="cb22-7"><a href="#cb22-7" aria-hidden="true"></a></span> 280<span id="cb22-7"><a href="#cb22-7"></a></span>
281<span id="cb22-8"><a href="#cb22-8" aria-hidden="true"></a><span class="at">#[</span>test<span class="at">]</span></span> 281<span id="cb22-8"><a href="#cb22-8"></a><span class="at">#[</span>test<span class="at">]</span></span>
282<span id="cb22-9"><a href="#cb22-9" aria-hidden="true"></a><span class="kw">fn</span> works() <span class="op">{</span></span> 282<span id="cb22-9"><a href="#cb22-9"></a><span class="kw">fn</span> works() <span class="op">{</span></span>
283<span id="cb22-10"><a href="#cb22-10" aria-hidden="true"></a> <span class="pp">assert!</span>(<span class="cn">true</span>)<span class="op">;</span></span> 283<span id="cb22-10"><a href="#cb22-10"></a> <span class="pp">assert!</span>(<span class="cn">true</span>);</span>
284<span id="cb22-11"><a href="#cb22-11" aria-hidden="true"></a><span class="op">}</span></span></code></pre></div> 284<span id="cb22-11"><a href="#cb22-11"></a><span class="op">}</span></span></code></pre></div>
285<p>You should find something like this in the output of <code>cargo test</code>:</p> 285<p>You should find something like this in the output of <code>cargo test</code>:</p>
286<pre><code>return move | y | move | z | { x + y + z }</code></pre> 286<pre><code>return move | y | move | z | { x + y + z }</code></pre>
287<p>Glorious <code>println!</code> debugging!</p> 287<p>Glorious <code>println!</code> debugging!</p>
288<h4 id="function-signature">Function signature</h4> 288<h4 id="function-signature">Function signature</h4>
289<p>This section gets into the more complicated bits of the macro, generating type aliases and the function signature. By the end of this section, we should have a full working auto-currying macro!</p> 289<p>This section gets into the more complicated bits of the macro, generating type aliases and the function signature. By the end of this section, we should have a full working auto-currying macro!</p>
290<p>Recall what our generated type aliases should look like, for our <code>add</code> function:</p> 290<p>Recall what our generated type aliases should look like, for our <code>add</code> function:</p>
291<div class="sourceCode" id="cb24"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb24-1"><a href="#cb24-1" aria-hidden="true"></a><span class="kw">type</span> T0 <span class="op">=</span> <span class="dt">u32</span><span class="op">;</span></span> 291<div class="sourceCode" id="cb24"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb24-1"><a href="#cb24-1"></a><span class="kw">type</span> T0 = <span class="dt">u32</span>;</span>
292<span id="cb24-2"><a href="#cb24-2" aria-hidden="true"></a><span class="kw">type</span> T1 <span class="op">=</span> <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) <span class="op">-&gt;</span> T0<span class="op">;</span></span> 292<span id="cb24-2"><a href="#cb24-2"></a><span class="kw">type</span> T1 = <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) -&gt; T0;</span>
293<span id="cb24-3"><a href="#cb24-3" aria-hidden="true"></a><span class="kw">type</span> T2 <span class="op">=</span> <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) <span class="op">-&gt;</span> T1<span class="op">;</span></span></code></pre></div> 293<span id="cb24-3"><a href="#cb24-3"></a><span class="kw">type</span> T2 = <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) -&gt; T1;</span></code></pre></div>
294<p>In general:</p> 294<p>In general:</p>
295<div class="sourceCode" id="cb25"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb25-1"><a href="#cb25-1" aria-hidden="true"></a><span class="kw">type</span> T0 <span class="op">=</span> <span class="op">&lt;</span><span class="kw">return</span> <span class="kw">type</span>&gt;<span class="op">;</span></span> 295<div class="sourceCode" id="cb25"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb25-1"><a href="#cb25-1"></a><span class="kw">type</span> T0 = &lt;<span class="kw">return</span> <span class="kw">type</span>&gt;;</span>
296<span id="cb25-2"><a href="#cb25-2" aria-hidden="true"></a><span class="kw">type</span> T1 <span class="op">=</span> <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="op">&lt;</span><span class="kw">type</span> of arg N&gt;) -&gt; T0<span class="op">;</span></span> 296<span id="cb25-2"><a href="#cb25-2"></a><span class="kw">type</span> T1 = <span class="kw">impl</span> <span class="bu">Fn</span>(&lt;<span class="kw">type</span> of arg N&gt;) -&gt; T0;</span>
297<span id="cb25-3"><a href="#cb25-3" aria-hidden="true"></a><span class="kw">type</span> T2 <span class="op">=</span> <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="op">&lt;</span><span class="kw">type</span> of arg N - 1&gt;) -&gt; T1<span class="op">;</span></span> 297<span id="cb25-3"><a href="#cb25-3"></a><span class="kw">type</span> T2 = <span class="kw">impl</span> <span class="bu">Fn</span>(&lt;<span class="kw">type</span> of arg N - 1&gt;) -&gt; T1;</span>
298<span id="cb25-4"><a href="#cb25-4" aria-hidden="true"></a><span class="op">.</span></span> 298<span id="cb25-4"><a href="#cb25-4"></a>.</span>
299<span id="cb25-5"><a href="#cb25-5" aria-hidden="true"></a><span class="op">.</span></span> 299<span id="cb25-5"><a href="#cb25-5"></a>.</span>
300<span id="cb25-6"><a href="#cb25-6" aria-hidden="true"></a><span class="op">.</span></span> 300<span id="cb25-6"><a href="#cb25-6"></a>.</span>
301<span id="cb25-7"><a href="#cb25-7" aria-hidden="true"></a><span class="kw">type</span> T(N-1) <span class="op">=</span> <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="op">&lt;</span><span class="kw">type</span> of arg 2&gt;) -&gt; T(N-2)<span class="op">;</span></span></code></pre></div> 301<span id="cb25-7"><a href="#cb25-7"></a><span class="kw">type</span> T(N-1) = <span class="kw">impl</span> <span class="bu">Fn</span>(&lt;<span class="kw">type</span> of arg 2&gt;) -&gt; T(N-2);</span></code></pre></div>
302<p>To codegen that, we need the types of:</p> 302<p>To codegen that, we need the types of:</p>
303<ul> 303<ul>
304<li>all our inputs (arguments)</li> 304<li>all our inputs (arguments)</li>
305<li>the output (the return type)</li> 305<li>the output (the return type)</li>
306</ul> 306</ul>
307<p>To fetch the types of all our inputs, we can simply reuse the bits we wrote to fetch the names of all our inputs! (doc: <a href="https://docs.rs/syn/1.0.18/syn/enum.Type.html">Type</a>)</p> 307<p>To fetch the types of all our inputs, we can simply reuse the bits we wrote to fetch the names of all our inputs! (doc: <a href="https://docs.rs/syn/1.0.18/syn/enum.Type.html">Type</a>)</p>
308<div class="sourceCode" id="cb26"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb26-1"><a href="#cb26-1" aria-hidden="true"></a><span class="co">// src/lib.rs</span></span> 308<div class="sourceCode" id="cb26"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb26-1"><a href="#cb26-1"></a><span class="co">// src/lib.rs</span></span>
309<span id="cb26-2"><a href="#cb26-2" aria-hidden="true"></a></span> 309<span id="cb26-2"><a href="#cb26-2"></a></span>
310<span id="cb26-3"><a href="#cb26-3" aria-hidden="true"></a><span class="kw">use</span> <span class="pp">syn::</span><span class="op">{</span>parse_macro_input<span class="op">,</span> Block<span class="op">,</span> FnArg<span class="op">,</span> ItemFn<span class="op">,</span> Pat<span class="op">,</span> ReturnType<span class="op">,</span> Type<span class="op">};</span></span> 310<span id="cb26-3"><a href="#cb26-3"></a><span class="kw">use</span> <span class="pp">syn::</span><span class="op">{</span>parse_macro_input, Block, FnArg, ItemFn, Pat, ReturnType, Type<span class="op">}</span>;</span>
311<span id="cb26-4"><a href="#cb26-4" aria-hidden="true"></a></span> 311<span id="cb26-4"><a href="#cb26-4"></a></span>
312<span id="cb26-5"><a href="#cb26-5" aria-hidden="true"></a><span class="kw">fn</span> extract_type(a<span class="op">:</span> FnArg) <span class="op">-&gt;</span> <span class="dt">Box</span><span class="op">&lt;</span>Type<span class="op">&gt;</span> <span class="op">{</span></span> 312<span id="cb26-5"><a href="#cb26-5"></a><span class="kw">fn</span> extract_type(a: FnArg) -&gt; <span class="dt">Box</span>&lt;Type&gt; <span class="op">{</span></span>
313<span id="cb26-6"><a href="#cb26-6" aria-hidden="true"></a> <span class="kw">match</span> a <span class="op">{</span></span> 313<span id="cb26-6"><a href="#cb26-6"></a> <span class="kw">match</span> a <span class="op">{</span></span>
314<span id="cb26-7"><a href="#cb26-7" aria-hidden="true"></a> <span class="pp">FnArg::</span>Typed(p) <span class="op">=&gt;</span> p<span class="op">.</span>ty<span class="op">,</span> <span class="co">// notice `ty` instead of `pat`</span></span> 314<span id="cb26-7"><a href="#cb26-7"></a> <span class="pp">FnArg::</span>Typed(p) =&gt; p.ty, <span class="co">// notice `ty` instead of `pat`</span></span>
315<span id="cb26-8"><a href="#cb26-8" aria-hidden="true"></a> _ <span class="op">=&gt;</span> <span class="pp">panic!</span>(<span class="st">&quot;Not supported on types with `self`!&quot;</span>)<span class="op">,</span></span> 315<span id="cb26-8"><a href="#cb26-8"></a> _ =&gt; <span class="pp">panic!</span>(<span class="st">&quot;Not supported on types with `self`!&quot;</span>),</span>
316<span id="cb26-9"><a href="#cb26-9" aria-hidden="true"></a> <span class="op">}</span></span> 316<span id="cb26-9"><a href="#cb26-9"></a> <span class="op">}</span></span>
317<span id="cb26-10"><a href="#cb26-10" aria-hidden="true"></a><span class="op">}</span></span> 317<span id="cb26-10"><a href="#cb26-10"></a><span class="op">}</span></span>
318<span id="cb26-11"><a href="#cb26-11" aria-hidden="true"></a></span> 318<span id="cb26-11"><a href="#cb26-11"></a></span>
319<span id="cb26-12"><a href="#cb26-12" aria-hidden="true"></a><span class="kw">fn</span> extract_arg_types(fn_args<span class="op">:</span> Punctuated<span class="op">&lt;</span>FnArg<span class="op">,</span> <span class="pp">syn::token::</span>Comma<span class="op">&gt;</span>) <span class="op">-&gt;</span> <span class="dt">Vec</span><span class="op">&lt;</span><span class="dt">Box</span><span class="op">&lt;</span>Type<span class="op">&gt;&gt;</span> <span class="op">{</span></span> 319<span id="cb26-12"><a href="#cb26-12"></a><span class="kw">fn</span> extract_arg_types(fn_args: Punctuated&lt;FnArg, <span class="pp">syn::token::</span>Comma&gt;) -&gt; <span class="dt">Vec</span>&lt;<span class="dt">Box</span>&lt;Type&gt;&gt; <span class="op">{</span></span>
320<span id="cb26-13"><a href="#cb26-13" aria-hidden="true"></a> <span class="kw">return</span> fn_args<span class="op">.</span>into_iter()<span class="op">.</span>map(extract_type)<span class="op">.</span><span class="pp">collect::</span><span class="op">&lt;</span><span class="dt">Vec</span><span class="op">&lt;</span>_<span class="op">&gt;&gt;</span>()<span class="op">;</span></span> 320<span id="cb26-13"><a href="#cb26-13"></a> <span class="kw">return</span> fn_args.into_iter().map(extract_type).<span class="pp">collect::</span>&lt;<span class="dt">Vec</span>&lt;_&gt;&gt;();</span>
321<span id="cb26-14"><a href="#cb26-14" aria-hidden="true"></a></span> 321<span id="cb26-14"><a href="#cb26-14"></a></span>
322<span id="cb26-15"><a href="#cb26-15" aria-hidden="true"></a><span class="op">}</span></span></code></pre></div> 322<span id="cb26-15"><a href="#cb26-15"></a><span class="op">}</span></span></code></pre></div>
323<p>A good reader would have looked at the docs for output member of the <code>syn::Signature</code> struct. It has the type <code>syn::ReturnType</code>. So there is no extraction to do here right? There are actually a couple of things we have to ensure here:</p> 323<p>A good reader would have looked at the docs for output member of the <code>syn::Signature</code> struct. It has the type <code>syn::ReturnType</code>. So there is no extraction to do here right? There are actually a couple of things we have to ensure here:</p>
324<ol type="1"> 324<ol type="1">
325<li><p>We need to ensure that the function returns! A function that does not return is pointless in this case, and I will tell you why, in the <a href="#notes">Notes</a> section.</p></li> 325<li><p>We need to ensure that the function returns! A function that does not return is pointless in this case, and I will tell you why, in the <a href="#notes">Notes</a> section.</p></li>
326<li><p>A <code>ReturnType</code> encloses the arrow of the return as well, we need to get rid of that. Recall:</p> 326<li><p>A <code>ReturnType</code> encloses the arrow of the return as well, we need to get rid of that. Recall:</p>
327<div class="sourceCode" id="cb27"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb27-1"><a href="#cb27-1" aria-hidden="true"></a><span class="kw">type</span> T0 <span class="op">=</span> <span class="dt">u32</span></span> 327<div class="sourceCode" id="cb27"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb27-1"><a href="#cb27-1"></a><span class="kw">type</span> T0 = <span class="dt">u32</span></span>
328<span id="cb27-2"><a href="#cb27-2" aria-hidden="true"></a><span class="co">// and not</span></span> 328<span id="cb27-2"><a href="#cb27-2"></a><span class="co">// and not</span></span>
329<span id="cb27-3"><a href="#cb27-3" aria-hidden="true"></a><span class="kw">type</span> T0 <span class="op">=</span> <span class="op">-&gt;</span> <span class="dt">u32</span></span></code></pre></div></li> 329<span id="cb27-3"><a href="#cb27-3"></a><span class="kw">type</span> T0 = -&gt; <span class="dt">u32</span></span></code></pre></div></li>
330</ol> 330</ol>
331<p>Here is the snippet that handles extraction of the return type (doc: <a href="https://docs.rs/syn/1.0.19/syn/enum.ReturnType.html">syn::ReturnType</a>):</p> 331<p>Here is the snippet that handles extraction of the return type (doc: <a href="https://docs.rs/syn/1.0.19/syn/enum.ReturnType.html">syn::ReturnType</a>):</p>
332<div class="sourceCode" id="cb28"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb28-1"><a href="#cb28-1" aria-hidden="true"></a><span class="co">// src/lib.rs</span></span> 332<div class="sourceCode" id="cb28"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb28-1"><a href="#cb28-1"></a><span class="co">// src/lib.rs</span></span>
333<span id="cb28-2"><a href="#cb28-2" aria-hidden="true"></a></span> 333<span id="cb28-2"><a href="#cb28-2"></a></span>
334<span id="cb28-3"><a href="#cb28-3" aria-hidden="true"></a><span class="kw">fn</span> extract_return_type(a<span class="op">:</span> ReturnType) <span class="op">-&gt;</span> <span class="dt">Box</span><span class="op">&lt;</span>Type<span class="op">&gt;</span> <span class="op">{</span></span> 334<span id="cb28-3"><a href="#cb28-3"></a><span class="kw">fn</span> extract_return_type(a: ReturnType) -&gt; <span class="dt">Box</span>&lt;Type&gt; <span class="op">{</span></span>
335<span id="cb28-4"><a href="#cb28-4" aria-hidden="true"></a> <span class="kw">match</span> a <span class="op">{</span></span> 335<span id="cb28-4"><a href="#cb28-4"></a> <span class="kw">match</span> a <span class="op">{</span></span>
336<span id="cb28-5"><a href="#cb28-5" aria-hidden="true"></a> <span class="pp">ReturnType::</span>Type(_<span class="op">,</span> p) <span class="op">=&gt;</span> p<span class="op">,</span></span> 336<span id="cb28-5"><a href="#cb28-5"></a> <span class="pp">ReturnType::</span>Type(_, p) =&gt; p,</span>
337<span id="cb28-6"><a href="#cb28-6" aria-hidden="true"></a> _ <span class="op">=&gt;</span> <span class="pp">panic!</span>(<span class="st">&quot;Not supported on functions without return types!&quot;</span>)<span class="op">,</span></span> 337<span id="cb28-6"><a href="#cb28-6"></a> _ =&gt; <span class="pp">panic!</span>(<span class="st">&quot;Not supported on functions without return types!&quot;</span>),</span>
338<span id="cb28-7"><a href="#cb28-7" aria-hidden="true"></a> <span class="op">}</span></span> 338<span id="cb28-7"><a href="#cb28-7"></a> <span class="op">}</span></span>
339<span id="cb28-8"><a href="#cb28-8" aria-hidden="true"></a><span class="op">}</span></span></code></pre></div> 339<span id="cb28-8"><a href="#cb28-8"></a><span class="op">}</span></span></code></pre></div>
340<p>You might notice that we are making extensive use of the <code>panic!</code> macro. Well, that is because it is a good idea to quit on receiving an unsatisfactory <code>TokenStream</code>.</p> 340<p>You might notice that we are making extensive use of the <code>panic!</code> macro. Well, that is because it is a good idea to quit on receiving an unsatisfactory <code>TokenStream</code>.</p>
341<p>With all our types ready, we can get on with generating type aliases:</p> 341<p>With all our types ready, we can get on with generating type aliases:</p>
342<div class="sourceCode" id="cb29"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb29-1"><a href="#cb29-1" aria-hidden="true"></a><span class="co">// src/lib.rs</span></span> 342<div class="sourceCode" id="cb29"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb29-1"><a href="#cb29-1"></a><span class="co">// src/lib.rs</span></span>
343<span id="cb29-2"><a href="#cb29-2" aria-hidden="true"></a></span> 343<span id="cb29-2"><a href="#cb29-2"></a></span>
344<span id="cb29-3"><a href="#cb29-3" aria-hidden="true"></a><span class="kw">use</span> <span class="pp">quote::</span><span class="op">{</span>quote<span class="op">,</span> format_ident<span class="op">};</span></span> 344<span id="cb29-3"><a href="#cb29-3"></a><span class="kw">use</span> <span class="pp">quote::</span><span class="op">{</span>quote, format_ident<span class="op">}</span>;</span>
345<span id="cb29-4"><a href="#cb29-4" aria-hidden="true"></a></span> 345<span id="cb29-4"><a href="#cb29-4"></a></span>
346<span id="cb29-5"><a href="#cb29-5" aria-hidden="true"></a><span class="kw">fn</span> generate_type_aliases(</span> 346<span id="cb29-5"><a href="#cb29-5"></a><span class="kw">fn</span> generate_type_aliases(</span>
347<span id="cb29-6"><a href="#cb29-6" aria-hidden="true"></a> fn_arg_types<span class="op">:</span> <span class="op">&amp;</span>[<span class="dt">Box</span><span class="op">&lt;</span>Type<span class="op">&gt;</span>]<span class="op">,</span></span> 347<span id="cb29-6"><a href="#cb29-6"></a> fn_arg_types: &amp;<span class="op">[</span><span class="dt">Box</span>&lt;Type&gt;<span class="op">]</span>,</span>
348<span id="cb29-7"><a href="#cb29-7" aria-hidden="true"></a> fn_return_type<span class="op">:</span> <span class="dt">Box</span><span class="op">&lt;</span>Type<span class="op">&gt;,</span></span> 348<span id="cb29-7"><a href="#cb29-7"></a> fn_return_type: <span class="dt">Box</span>&lt;Type&gt;,</span>
349<span id="cb29-8"><a href="#cb29-8" aria-hidden="true"></a> fn_name<span class="op">:</span> <span class="op">&amp;</span><span class="pp">syn::</span>Ident<span class="op">,</span></span> 349<span id="cb29-8"><a href="#cb29-8"></a> fn_name: &amp;<span class="pp">syn::</span>Ident,</span>
350<span id="cb29-9"><a href="#cb29-9" aria-hidden="true"></a>) <span class="op">-&gt;</span> <span class="dt">Vec</span><span class="op">&lt;</span><span class="pp">proc_macro2::</span>TokenStream<span class="op">&gt;</span> <span class="op">{</span> <span class="co">// 1</span></span> 350<span id="cb29-9"><a href="#cb29-9"></a>) -&gt; <span class="dt">Vec</span>&lt;<span class="pp">proc_macro2::</span>TokenStream&gt; <span class="op">{</span> <span class="co">// 1</span></span>
351<span id="cb29-10"><a href="#cb29-10" aria-hidden="true"></a></span> 351<span id="cb29-10"><a href="#cb29-10"></a></span>
352<span id="cb29-11"><a href="#cb29-11" aria-hidden="true"></a> <span class="kw">let</span> type_t0 <span class="op">=</span> <span class="pp">format_ident!</span>(<span class="st">&quot;_{}_T0&quot;</span><span class="op">,</span> fn_name)<span class="op">;</span> <span class="co">// 2</span></span> 352<span id="cb29-11"><a href="#cb29-11"></a> <span class="kw">let</span> type_t0 = <span class="pp">format_ident!</span>(<span class="st">&quot;_{}_T0&quot;</span>, fn_name); <span class="co">// 2</span></span>
353<span id="cb29-12"><a href="#cb29-12" aria-hidden="true"></a> <span class="kw">let</span> <span class="kw">mut</span> type_aliases <span class="op">=</span> <span class="pp">vec!</span>[<span class="pp">quote!</span> <span class="op">{</span> <span class="kw">type</span> #type_t0 <span class="op">=</span> #fn_return_type <span class="op">}</span>]<span class="op">;</span></span> 353<span id="cb29-12"><a href="#cb29-12"></a> <span class="kw">let</span> <span class="kw">mut</span> type_aliases = <span class="pp">vec!</span><span class="op">[</span><span class="pp">quote!</span> <span class="op">{</span> <span class="kw">type</span> #type_t0 = #fn_return_type <span class="op">}]</span>;</span>
354<span id="cb29-13"><a href="#cb29-13" aria-hidden="true"></a></span> 354<span id="cb29-13"><a href="#cb29-13"></a></span>
355<span id="cb29-14"><a href="#cb29-14" aria-hidden="true"></a> <span class="co">// 3</span></span> 355<span id="cb29-14"><a href="#cb29-14"></a> <span class="co">// 3</span></span>
356<span id="cb29-15"><a href="#cb29-15" aria-hidden="true"></a> <span class="kw">for</span> (i<span class="op">,</span> t) <span class="kw">in</span> (<span class="dv">1</span><span class="op">..</span>)<span class="op">.</span>zip(fn_arg_types<span class="op">.</span>into_iter()<span class="op">.</span>rev()) <span class="op">{</span></span> 356<span id="cb29-15"><a href="#cb29-15"></a> <span class="kw">for</span> (i, t) <span class="kw">in</span> (<span class="dv">1</span>..).zip(fn_arg_types.into_iter().rev()) <span class="op">{</span></span>
357<span id="cb29-16"><a href="#cb29-16" aria-hidden="true"></a> <span class="kw">let</span> p <span class="op">=</span> <span class="pp">format_ident!</span>(<span class="st">&quot;_{}_{}&quot;</span><span class="op">,</span> fn_name<span class="op">,</span> <span class="pp">format!</span>(<span class="st">&quot;T{}&quot;</span><span class="op">,</span> i <span class="op">-</span> <span class="dv">1</span>))<span class="op">;</span></span> 357<span id="cb29-16"><a href="#cb29-16"></a> <span class="kw">let</span> p = <span class="pp">format_ident!</span>(<span class="st">&quot;_{}_{}&quot;</span>, fn_name, <span class="pp">format!</span>(<span class="st">&quot;T{}&quot;</span>, i - <span class="dv">1</span>));</span>
358<span id="cb29-17"><a href="#cb29-17" aria-hidden="true"></a> <span class="kw">let</span> n <span class="op">=</span> <span class="pp">format_ident!</span>(<span class="st">&quot;_{}_{}&quot;</span><span class="op">,</span> fn_name<span class="op">,</span> <span class="pp">format!</span>(<span class="st">&quot;T{}&quot;</span><span class="op">,</span> i))<span class="op">;</span></span> 358<span id="cb29-17"><a href="#cb29-17"></a> <span class="kw">let</span> n = <span class="pp">format_ident!</span>(<span class="st">&quot;_{}_{}&quot;</span>, fn_name, <span class="pp">format!</span>(<span class="st">&quot;T{}&quot;</span>, i));</span>
359<span id="cb29-18"><a href="#cb29-18" aria-hidden="true"></a></span> 359<span id="cb29-18"><a href="#cb29-18"></a></span>
360<span id="cb29-19"><a href="#cb29-19" aria-hidden="true"></a> type_aliases<span class="op">.</span>push(<span class="pp">quote!</span> <span class="op">{</span></span> 360<span id="cb29-19"><a href="#cb29-19"></a> type_aliases.push(<span class="pp">quote!</span> <span class="op">{</span></span>
361<span id="cb29-20"><a href="#cb29-20" aria-hidden="true"></a> <span class="kw">type</span> #n <span class="op">=</span> <span class="kw">impl</span> <span class="bu">Fn</span>(#t) <span class="op">-&gt;</span> #p</span> 361<span id="cb29-20"><a href="#cb29-20"></a> <span class="kw">type</span> #n = <span class="kw">impl</span> <span class="bu">Fn</span>(#t) -&gt; #p</span>
362<span id="cb29-21"><a href="#cb29-21" aria-hidden="true"></a> <span class="op">}</span>)<span class="op">;</span></span> 362<span id="cb29-21"><a href="#cb29-21"></a> <span class="op">}</span>);</span>
363<span id="cb29-22"><a href="#cb29-22" aria-hidden="true"></a> <span class="op">}</span></span> 363<span id="cb29-22"><a href="#cb29-22"></a> <span class="op">}</span></span>
364<span id="cb29-23"><a href="#cb29-23" aria-hidden="true"></a></span> 364<span id="cb29-23"><a href="#cb29-23"></a></span>
365<span id="cb29-24"><a href="#cb29-24" aria-hidden="true"></a> <span class="kw">return</span> type_aliases<span class="op">;</span></span> 365<span id="cb29-24"><a href="#cb29-24"></a> <span class="kw">return</span> type_aliases;</span>
366<span id="cb29-25"><a href="#cb29-25" aria-hidden="true"></a><span class="op">}</span></span></code></pre></div> 366<span id="cb29-25"><a href="#cb29-25"></a><span class="op">}</span></span></code></pre></div>
367<p><strong>1. The return value</strong><br /> 367<p><strong>1. The return value</strong><br />
368We are returning a <code>Vec&lt;proc_macro2::TokenStream&gt;</code>, i. e., a list of <code>TokenStream</code>s, where each item is a type alias.</p> 368We are returning a <code>Vec&lt;proc_macro2::TokenStream&gt;</code>, i. e., a list of <code>TokenStream</code>s, where each item is a type alias.</p>
369<p><strong>2. Format identifier?</strong><br /> 369<p><strong>2. Format identifier?</strong><br />
370I’ve got some explanation to do on this line. Clearly, we are trying to write the first type alias, and initialize our <code>TokenStream</code> vector with <code>T0</code>, because it is different from the others:</p> 370I’ve got some explanation to do on this line. Clearly, we are trying to write the first type alias, and initialize our <code>TokenStream</code> vector with <code>T0</code>, because it is different from the others:</p>
371<div class="sourceCode" id="cb30"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb30-1"><a href="#cb30-1" aria-hidden="true"></a><span class="kw">type</span> T0 <span class="op">=</span> something</span> 371<div class="sourceCode" id="cb30"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb30-1"><a href="#cb30-1"></a><span class="kw">type</span> T0 = something</span>
372<span id="cb30-2"><a href="#cb30-2" aria-hidden="true"></a><span class="co">// the others are of the form</span></span> 372<span id="cb30-2"><a href="#cb30-2"></a><span class="co">// the others are of the form</span></span>
373<span id="cb30-3"><a href="#cb30-3" aria-hidden="true"></a><span class="kw">type</span> Tr <span class="op">=</span> <span class="kw">impl</span> <span class="bu">Fn</span>(something) <span class="op">-&gt;</span> something</span></code></pre></div> 373<span id="cb30-3"><a href="#cb30-3"></a><span class="kw">type</span> Tr = <span class="kw">impl</span> <span class="bu">Fn</span>(something) -&gt; something</span></code></pre></div>
374<p><code>format_ident!</code> is similar to <code>format!</code>. Instead of returning a formatted string, it returns a <code>syn::Ident</code>. Therefore, <code>type_t0</code> is actually an identifier for, in the case of our <code>add</code> function, <code>_add_T0</code>. Why is this formatting important? Namespacing.</p> 374<p><code>format_ident!</code> is similar to <code>format!</code>. Instead of returning a formatted string, it returns a <code>syn::Ident</code>. Therefore, <code>type_t0</code> is actually an identifier for, in the case of our <code>add</code> function, <code>_add_T0</code>. Why is this formatting important? Namespacing.</p>
375<p>Picture this, we have two functions, <code>add</code> and <code>subtract</code>, that we wish to curry with our macro:</p> 375<p>Picture this, we have two functions, <code>add</code> and <code>subtract</code>, that we wish to curry with our macro:</p>
376<div class="sourceCode" id="cb31"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb31-1"><a href="#cb31-1" aria-hidden="true"></a><span class="at">#[</span>curry<span class="at">]</span></span> 376<div class="sourceCode" id="cb31"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb31-1"><a href="#cb31-1"></a><span class="at">#[</span>curry<span class="at">]</span></span>
377<span id="cb31-2"><a href="#cb31-2" aria-hidden="true"></a><span class="kw">fn</span> add(<span class="op">...</span>) <span class="op">-&gt;</span> <span class="dt">u32</span> <span class="op">{</span> <span class="op">...</span> <span class="op">}</span></span> 377<span id="cb31-2"><a href="#cb31-2"></a><span class="kw">fn</span> add(...) -&gt; <span class="dt">u32</span> <span class="op">{</span> ... <span class="op">}</span></span>
378<span id="cb31-3"><a href="#cb31-3" aria-hidden="true"></a></span> 378<span id="cb31-3"><a href="#cb31-3"></a></span>
379<span id="cb31-4"><a href="#cb31-4" aria-hidden="true"></a><span class="at">#[</span>curry<span class="at">]</span></span> 379<span id="cb31-4"><a href="#cb31-4"></a><span class="at">#[</span>curry<span class="at">]</span></span>
380<span id="cb31-5"><a href="#cb31-5" aria-hidden="true"></a><span class="kw">fn</span> sub(<span class="op">...</span>) <span class="op">-&gt;</span> <span class="dt">u32</span> <span class="op">{</span> <span class="op">...</span> <span class="op">}</span></span></code></pre></div> 380<span id="cb31-5"><a href="#cb31-5"></a><span class="kw">fn</span> sub(...) -&gt; <span class="dt">u32</span> <span class="op">{</span> ... <span class="op">}</span></span></code></pre></div>
381<p>Here is the same but with macros expanded:</p> 381<p>Here is the same but with macros expanded:</p>
382<div class="sourceCode" id="cb32"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb32-1"><a href="#cb32-1" aria-hidden="true"></a><span class="kw">type</span> T0 <span class="op">=</span> <span class="dt">u32</span><span class="op">;</span></span> 382<div class="sourceCode" id="cb32"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb32-1"><a href="#cb32-1"></a><span class="kw">type</span> T0 = <span class="dt">u32</span>;</span>
383<span id="cb32-2"><a href="#cb32-2" aria-hidden="true"></a><span class="kw">type</span> T1 <span class="op">=</span> <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) <span class="op">-&gt;</span> T0<span class="op">;</span></span> 383<span id="cb32-2"><a href="#cb32-2"></a><span class="kw">type</span> T1 = <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) -&gt; T0;</span>
384<span id="cb32-3"><a href="#cb32-3" aria-hidden="true"></a><span class="kw">fn</span> add( <span class="op">...</span> ) <span class="op">-&gt;</span> T1 <span class="op">{</span> <span class="op">...</span> <span class="op">}</span></span> 384<span id="cb32-3"><a href="#cb32-3"></a><span class="kw">fn</span> add( ... ) -&gt; T1 <span class="op">{</span> ... <span class="op">}</span></span>
385<span id="cb32-4"><a href="#cb32-4" aria-hidden="true"></a></span> 385<span id="cb32-4"><a href="#cb32-4"></a></span>
386<span id="cb32-5"><a href="#cb32-5" aria-hidden="true"></a><span class="kw">type</span> T0 <span class="op">=</span> <span class="dt">u32</span><span class="op">;</span></span> 386<span id="cb32-5"><a href="#cb32-5"></a><span class="kw">type</span> T0 = <span class="dt">u32</span>;</span>
387<span id="cb32-6"><a href="#cb32-6" aria-hidden="true"></a><span class="kw">type</span> T1 <span class="op">=</span> <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) <span class="op">-&gt;</span> T0<span class="op">;</span></span> 387<span id="cb32-6"><a href="#cb32-6"></a><span class="kw">type</span> T1 = <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) -&gt; T0;</span>
388<span id="cb32-7"><a href="#cb32-7" aria-hidden="true"></a><span class="kw">fn</span> sub( <span class="op">...</span> ) <span class="op">-&gt;</span> T1 <span class="op">{</span> <span class="op">...</span> <span class="op">}</span></span></code></pre></div> 388<span id="cb32-7"><a href="#cb32-7"></a><span class="kw">fn</span> sub( ... ) -&gt; T1 <span class="op">{</span> ... <span class="op">}</span></span></code></pre></div>
389<p>We end up with two definitions of <code>T0</code>! Now, if we do the little <code>format_ident!</code> dance we did up there:</p> 389<p>We end up with two definitions of <code>T0</code>! Now, if we do the little <code>format_ident!</code> dance we did up there:</p>
390<div class="sourceCode" id="cb33"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb33-1"><a href="#cb33-1" aria-hidden="true"></a><span class="kw">type</span> _add_T0 <span class="op">=</span> <span class="dt">u32</span><span class="op">;</span></span> 390<div class="sourceCode" id="cb33"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb33-1"><a href="#cb33-1"></a><span class="kw">type</span> _add_T0 = <span class="dt">u32</span>;</span>
391<span id="cb33-2"><a href="#cb33-2" aria-hidden="true"></a><span class="kw">type</span> _add_T1 <span class="op">=</span> <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) <span class="op">-&gt;</span> _add_T0<span class="op">;</span></span> 391<span id="cb33-2"><a href="#cb33-2"></a><span class="kw">type</span> _add_T1 = <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) -&gt; _add_T0;</span>
392<span id="cb33-3"><a href="#cb33-3" aria-hidden="true"></a><span class="kw">fn</span> add( <span class="op">...</span> ) <span class="op">-&gt;</span> _add_T1 <span class="op">{</span> <span class="op">...</span> <span class="op">}</span></span> 392<span id="cb33-3"><a href="#cb33-3"></a><span class="kw">fn</span> add( ... ) -&gt; _add_T1 <span class="op">{</span> ... <span class="op">}</span></span>
393<span id="cb33-4"><a href="#cb33-4" aria-hidden="true"></a></span> 393<span id="cb33-4"><a href="#cb33-4"></a></span>
394<span id="cb33-5"><a href="#cb33-5" aria-hidden="true"></a><span class="kw">type</span> _sub_T0 <span class="op">=</span> <span class="dt">u32</span><span class="op">;</span></span> 394<span id="cb33-5"><a href="#cb33-5"></a><span class="kw">type</span> _sub_T0 = <span class="dt">u32</span>;</span>
395<span id="cb33-6"><a href="#cb33-6" aria-hidden="true"></a><span class="kw">type</span> _sub_T1 <span class="op">=</span> <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) <span class="op">-&gt;</span> _sub_T0<span class="op">;</span></span> 395<span id="cb33-6"><a href="#cb33-6"></a><span class="kw">type</span> _sub_T1 = <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) -&gt; _sub_T0;</span>
396<span id="cb33-7"><a href="#cb33-7" aria-hidden="true"></a><span class="kw">fn</span> sub( <span class="op">...</span> ) <span class="op">-&gt;</span> _sub_T1 <span class="op">{</span> <span class="op">...</span> <span class="op">}</span></span></code></pre></div> 396<span id="cb33-7"><a href="#cb33-7"></a><span class="kw">fn</span> sub( ... ) -&gt; _sub_T1 <span class="op">{</span> ... <span class="op">}</span></span></code></pre></div>
397<p>Voilà! The type aliases don’t tread on each other. Remember to import <code>format_ident</code> from the <code>quote</code> crate.</p> 397<p>Voilà! The type aliases don’t tread on each other. Remember to import <code>format_ident</code> from the <code>quote</code> crate.</p>
398<p><strong>3. The TokenStream Vector</strong></p> 398<p><strong>3. The TokenStream Vector</strong></p>
399<p>We iterate over our types in reverse order (<code>T0</code> is the last return, <code>T1</code> is the second last, so on), assign a number to each iteration with <code>zip</code>, generate type names with <code>format_ident</code>, push a <code>TokenStream</code> with the help of <code>quote</code> and variable interpolation.</p> 399<p>We iterate over our types in reverse order (<code>T0</code> is the last return, <code>T1</code> is the second last, so on), assign a number to each iteration with <code>zip</code>, generate type names with <code>format_ident</code>, push a <code>TokenStream</code> with the help of <code>quote</code> and variable interpolation.</p>
400<p>If you are wondering why we used <code>(1..).zip()</code> instead of <code>.enumerate()</code>, it’s because we wanted to start counting from 1 instead of 0 (we are already done with <code>T0</code>!).</p> 400<p>If you are wondering why we used <code>(1..).zip()</code> instead of <code>.enumerate()</code>, it’s because we wanted to start counting from 1 instead of 0 (we are already done with <code>T0</code>!).</p>
401<h4 id="getting-it-together">Getting it together</h4> 401<h4 id="getting-it-together">Getting it together</h4>
402<p>I promised we’d have a fully working macro by the end of last section. I lied, we have to tie everything together in our <code>generate_curry</code> function:</p> 402<p>I promised we’d have a fully working macro by the end of last section. I lied, we have to tie everything together in our <code>generate_curry</code> function:</p>
403<div class="sourceCode" id="cb34"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb34-1"><a href="#cb34-1" aria-hidden="true"></a><span class="co">// src/lib.rs</span></span> 403<div class="sourceCode" id="cb34"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb34-1"><a href="#cb34-1"></a><span class="co">// src/lib.rs</span></span>
404<span id="cb34-2"><a href="#cb34-2" aria-hidden="true"></a></span> 404<span id="cb34-2"><a href="#cb34-2"></a></span>
405<span id="cb34-3"><a href="#cb34-3" aria-hidden="true"></a> <span class="kw">fn</span> generate_curry(parsed<span class="op">:</span> ItemFn) <span class="op">-&gt;</span> <span class="pp">proc_macro2::</span>TokenStream <span class="op">{</span></span> 405<span id="cb34-3"><a href="#cb34-3"></a> <span class="kw">fn</span> generate_curry(parsed: ItemFn) -&gt; <span class="pp">proc_macro2::</span>TokenStream <span class="op">{</span></span>
406<span id="cb34-4"><a href="#cb34-4" aria-hidden="true"></a> <span class="kw">let</span> fn_body <span class="op">=</span> parsed<span class="op">.</span>block<span class="op">;</span></span> 406<span id="cb34-4"><a href="#cb34-4"></a> <span class="kw">let</span> fn_body = parsed.block;</span>
407<span id="cb34-5"><a href="#cb34-5" aria-hidden="true"></a> <span class="kw">let</span> sig <span class="op">=</span> parsed<span class="op">.</span>sig<span class="op">;</span></span> 407<span id="cb34-5"><a href="#cb34-5"></a> <span class="kw">let</span> sig = parsed.sig;</span>
408<span id="cb34-6"><a href="#cb34-6" aria-hidden="true"></a> <span class="kw">let</span> vis <span class="op">=</span> parsed<span class="op">.</span>vis<span class="op">;</span></span> 408<span id="cb34-6"><a href="#cb34-6"></a> <span class="kw">let</span> vis = parsed.vis;</span>
409<span id="cb34-7"><a href="#cb34-7" aria-hidden="true"></a> <span class="kw">let</span> fn_name <span class="op">=</span> sig<span class="op">.</span>ident<span class="op">;</span></span> 409<span id="cb34-7"><a href="#cb34-7"></a> <span class="kw">let</span> fn_name = sig.ident;</span>
410<span id="cb34-8"><a href="#cb34-8" aria-hidden="true"></a> <span class="kw">let</span> fn_args <span class="op">=</span> sig<span class="op">.</span>inputs<span class="op">;</span></span> 410<span id="cb34-8"><a href="#cb34-8"></a> <span class="kw">let</span> fn_args = sig.inputs;</span>
411<span id="cb34-9"><a href="#cb34-9" aria-hidden="true"></a> <span class="kw">let</span> fn_return_type <span class="op">=</span> sig<span class="op">.</span>output<span class="op">;</span></span> 411<span id="cb34-9"><a href="#cb34-9"></a> <span class="kw">let</span> fn_return_type = sig.output;</span>
412<span id="cb34-10"><a href="#cb34-10" aria-hidden="true"></a></span> 412<span id="cb34-10"><a href="#cb34-10"></a></span>
413<span id="cb34-11"><a href="#cb34-11" aria-hidden="true"></a> <span class="kw">let</span> arg_idents <span class="op">=</span> extract_arg_idents(fn_args<span class="op">.</span>clone())<span class="op">;</span></span> 413<span id="cb34-11"><a href="#cb34-11"></a> <span class="kw">let</span> arg_idents = extract_arg_idents(fn_args.clone());</span>
414<span id="cb34-12"><a href="#cb34-12" aria-hidden="true"></a> <span class="kw">let</span> first_ident <span class="op">=</span> <span class="op">&amp;</span>arg_idents<span class="op">.</span>first()<span class="op">.</span>unwrap()<span class="op">;</span></span> 414<span id="cb34-12"><a href="#cb34-12"></a> <span class="kw">let</span> first_ident = &amp;arg_idents.first().unwrap();</span>
415<span id="cb34-13"><a href="#cb34-13" aria-hidden="true"></a> <span class="kw">let</span> curried_body <span class="op">=</span> generate_body(<span class="op">&amp;</span>arg_idents[<span class="dv">1</span><span class="op">..</span>]<span class="op">,</span> fn_body<span class="op">.</span>clone())<span class="op">;</span></span> 415<span id="cb34-13"><a href="#cb34-13"></a> <span class="kw">let</span> curried_body = generate_body(&amp;arg_idents<span class="op">[</span><span class="dv">1</span>..<span class="op">]</span>, fn_body.clone());</span>
416<span id="cb34-14"><a href="#cb34-14" aria-hidden="true"></a></span> 416<span id="cb34-14"><a href="#cb34-14"></a></span>
417<span id="cb34-15"><a href="#cb34-15" aria-hidden="true"></a><span class="op">+</span> <span class="kw">let</span> arg_types <span class="op">=</span> extract_arg_types(fn_args<span class="op">.</span>clone())<span class="op">;</span></span> 417<span id="cb34-15"><a href="#cb34-15"></a>+ <span class="kw">let</span> arg_types = extract_arg_types(fn_args.clone());</span>
418<span id="cb34-16"><a href="#cb34-16" aria-hidden="true"></a><span class="op">+</span> <span class="kw">let</span> first_type <span class="op">=</span> <span class="op">&amp;</span>arg_types<span class="op">.</span>first()<span class="op">.</span>unwrap()<span class="op">;</span></span> 418<span id="cb34-16"><a href="#cb34-16"></a>+ <span class="kw">let</span> first_type = &amp;arg_types.first().unwrap();</span>
419<span id="cb34-17"><a href="#cb34-17" aria-hidden="true"></a><span class="op">+</span> <span class="kw">let</span> type_aliases <span class="op">=</span> generate_type_aliases(</span> 419<span id="cb34-17"><a href="#cb34-17"></a>+ <span class="kw">let</span> type_aliases = generate_type_aliases(</span>
420<span id="cb34-18"><a href="#cb34-18" aria-hidden="true"></a><span class="op">+</span> <span class="op">&amp;</span>arg_types[<span class="dv">1</span><span class="op">..</span>]<span class="op">,</span></span> 420<span id="cb34-18"><a href="#cb34-18"></a>+ &amp;arg_types<span class="op">[</span><span class="dv">1</span>..<span class="op">]</span>,</span>
421<span id="cb34-19"><a href="#cb34-19" aria-hidden="true"></a><span class="op">+</span> extract_return_type(fn_return_type)<span class="op">,</span></span> 421<span id="cb34-19"><a href="#cb34-19"></a>+ extract_return_type(fn_return_type),</span>
422<span id="cb34-20"><a href="#cb34-20" aria-hidden="true"></a><span class="op">+</span> <span class="op">&amp;</span>fn_name<span class="op">,</span></span> 422<span id="cb34-20"><a href="#cb34-20"></a>+ &amp;fn_name,</span>
423<span id="cb34-21"><a href="#cb34-21" aria-hidden="true"></a><span class="op">+</span> )<span class="op">;</span></span> 423<span id="cb34-21"><a href="#cb34-21"></a>+ );</span>
424<span id="cb34-22"><a href="#cb34-22" aria-hidden="true"></a></span> 424<span id="cb34-22"><a href="#cb34-22"></a></span>
425<span id="cb34-23"><a href="#cb34-23" aria-hidden="true"></a><span class="op">+</span> <span class="kw">let</span> return_type <span class="op">=</span> <span class="pp">format_ident!</span>(<span class="st">&quot;_{}_{}&quot;</span><span class="op">,</span> <span class="op">&amp;</span>fn_name<span class="op">,</span> <span class="pp">format!</span>(<span class="st">&quot;T{}&quot;</span><span class="op">,</span> type_aliases<span class="op">.</span>len() <span class="op">-</span> <span class="dv">1</span>))<span class="op">;</span></span> 425<span id="cb34-23"><a href="#cb34-23"></a>+ <span class="kw">let</span> return_type = <span class="pp">format_ident!</span>(<span class="st">&quot;_{}_{}&quot;</span>, &amp;fn_name, <span class="pp">format!</span>(<span class="st">&quot;T{}&quot;</span>, type_aliases.len() - <span class="dv">1</span>));</span>
426<span id="cb34-24"><a href="#cb34-24" aria-hidden="true"></a></span> 426<span id="cb34-24"><a href="#cb34-24"></a></span>
427<span id="cb34-25"><a href="#cb34-25" aria-hidden="true"></a><span class="op">+</span> <span class="kw">return</span> <span class="pp">quote!</span> <span class="op">{</span></span> 427<span id="cb34-25"><a href="#cb34-25"></a>+ <span class="kw">return</span> <span class="pp">quote!</span> <span class="op">{</span></span>
428<span id="cb34-26"><a href="#cb34-26" aria-hidden="true"></a><span class="op">+</span> #(#type_aliases)<span class="op">;*</span> <span class="op">;</span></span> 428<span id="cb34-26"><a href="#cb34-26"></a>+ #(#type_aliases);* ;</span>
429<span id="cb34-27"><a href="#cb34-27" aria-hidden="true"></a><span class="op">+</span> #vis <span class="kw">fn</span> #fn_name (#first_ident<span class="op">:</span> #first_type) <span class="op">-&gt;</span> #return_type <span class="op">{</span></span> 429<span id="cb34-27"><a href="#cb34-27"></a>+ #vis <span class="kw">fn</span> #fn_name (#first_ident: #first_type) -&gt; #return_type <span class="op">{</span></span>
430<span id="cb34-28"><a href="#cb34-28" aria-hidden="true"></a><span class="op">+</span> #curried_body <span class="op">;</span></span> 430<span id="cb34-28"><a href="#cb34-28"></a>+ #curried_body ;</span>
431<span id="cb34-29"><a href="#cb34-29" aria-hidden="true"></a><span class="op">+</span> <span class="op">}</span></span> 431<span id="cb34-29"><a href="#cb34-29"></a>+ <span class="op">}</span></span>
432<span id="cb34-30"><a href="#cb34-30" aria-hidden="true"></a><span class="op">+</span> <span class="op">};</span></span> 432<span id="cb34-30"><a href="#cb34-30"></a>+ <span class="op">}</span>;</span>
433<span id="cb34-31"><a href="#cb34-31" aria-hidden="true"></a> <span class="op">}</span></span></code></pre></div> 433<span id="cb34-31"><a href="#cb34-31"></a> <span class="op">}</span></span></code></pre></div>
434<p>Most of the additions are self explanatory, I’ll go through the return statement with you. We are returning a <code>quote!{ ... }</code>, so a <code>proc_macro2::TokenStream</code>. We are iterating through the <code>type_aliases</code> variable, which you might recall, is a <code>Vec&lt;TokenStream&gt;</code>. You might notice the sneaky semicolon before the <code>*</code>. This basically tells <code>quote</code>, to insert an item, then a semicolon, and then the next one, another semicolon, and so on. The semicolon is a separator. We need to manually insert another semicolon at the end of it all, <code>quote</code> doesn’t insert a separator at the end of the iteration.</p> 434<p>Most of the additions are self explanatory, I’ll go through the return statement with you. We are returning a <code>quote!{ ... }</code>, so a <code>proc_macro2::TokenStream</code>. We are iterating through the <code>type_aliases</code> variable, which you might recall, is a <code>Vec&lt;TokenStream&gt;</code>. You might notice the sneaky semicolon before the <code>*</code>. This basically tells <code>quote</code>, to insert an item, then a semicolon, and then the next one, another semicolon, and so on. The semicolon is a separator. We need to manually insert another semicolon at the end of it all, <code>quote</code> doesn’t insert a separator at the end of the iteration.</p>
435<p>We retain the visibility and name of our original function. Our curried function takes as args, just the first argument of our original function. The return type of our curried function is actually, the last type alias we create. If you think back to our manually curried <code>add</code> function, we returned <code>T2</code>, which was in fact, the last type alias we created.</p> 435<p>We retain the visibility and name of our original function. Our curried function takes as args, just the first argument of our original function. The return type of our curried function is actually, the last type alias we create. If you think back to our manually curried <code>add</code> function, we returned <code>T2</code>, which was in fact, the last type alias we created.</p>
436<p>I am sure, at this point, you are itching to test this out, but before that, let me introduce you to some good methods of debugging proc-macro code.</p> 436<p>I am sure, at this point, you are itching to test this out, but before that, let me introduce you to some good methods of debugging proc-macro code.</p>
@@ -462,57 +462,57 @@ fn main() {
462<p>Writing proc-macros without <code>cargo-expand</code> is tantamount to driving a vehicle without rear view mirrors! Keep an eye on what is going on behind your back.</p> 462<p>Writing proc-macros without <code>cargo-expand</code> is tantamount to driving a vehicle without rear view mirrors! Keep an eye on what is going on behind your back.</p>
463<p>Now, your macro won’t always compile, you might just recieve the bee movie script as an error. <code>cargo-expand</code> will not work in such cases. I would suggest printing out your variables to inspect them. <code>TokenStream</code> implements <code>Display</code> as well as <code>Debug</code>. We don’t always have to be respectable programmers. Just print it.</p> 463<p>Now, your macro won’t always compile, you might just recieve the bee movie script as an error. <code>cargo-expand</code> will not work in such cases. I would suggest printing out your variables to inspect them. <code>TokenStream</code> implements <code>Display</code> as well as <code>Debug</code>. We don’t always have to be respectable programmers. Just print it.</p>
464<p>Enough of that, lets get testing:</p> 464<p>Enough of that, lets get testing:</p>
465<div class="sourceCode" id="cb37"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb37-1"><a href="#cb37-1" aria-hidden="true"></a><span class="co">// tests/smoke.rs</span></span> 465<div class="sourceCode" id="cb37"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb37-1"><a href="#cb37-1"></a><span class="co">// tests/smoke.rs</span></span>
466<span id="cb37-2"><a href="#cb37-2" aria-hidden="true"></a></span> 466<span id="cb37-2"><a href="#cb37-2"></a></span>
467<span id="cb37-3"><a href="#cb37-3" aria-hidden="true"></a><span class="at">#![</span>feature<span class="at">(</span>type_alias_impl_trait<span class="at">)]</span></span> 467<span id="cb37-3"><a href="#cb37-3"></a><span class="at">#![</span>feature<span class="at">(</span>type_alias_impl_trait<span class="at">)]</span></span>
468<span id="cb37-4"><a href="#cb37-4" aria-hidden="true"></a></span> 468<span id="cb37-4"><a href="#cb37-4"></a></span>
469<span id="cb37-5"><a href="#cb37-5" aria-hidden="true"></a><span class="at">#[</span><span class="pp">crate_name::</span>curry<span class="at">]</span></span> 469<span id="cb37-5"><a href="#cb37-5"></a><span class="at">#[</span><span class="pp">crate_name::</span>curry<span class="at">]</span></span>
470<span id="cb37-6"><a href="#cb37-6" aria-hidden="true"></a><span class="kw">fn</span> add(x<span class="op">:</span> <span class="dt">u32</span><span class="op">,</span> y<span class="op">:</span> <span class="dt">u32</span><span class="op">,</span> z<span class="op">:</span> <span class="dt">u32</span>) <span class="op">-&gt;</span> <span class="dt">u32</span> <span class="op">{</span></span> 470<span id="cb37-6"><a href="#cb37-6"></a><span class="kw">fn</span> add(x: <span class="dt">u32</span>, y: <span class="dt">u32</span>, z: <span class="dt">u32</span>) -&gt; <span class="dt">u32</span> <span class="op">{</span></span>
471<span id="cb37-7"><a href="#cb37-7" aria-hidden="true"></a> x <span class="op">+</span> y <span class="op">+</span> z</span> 471<span id="cb37-7"><a href="#cb37-7"></a> x + y + z</span>
472<span id="cb37-8"><a href="#cb37-8" aria-hidden="true"></a><span class="op">}</span></span> 472<span id="cb37-8"><a href="#cb37-8"></a><span class="op">}</span></span>
473<span id="cb37-9"><a href="#cb37-9" aria-hidden="true"></a></span> 473<span id="cb37-9"><a href="#cb37-9"></a></span>
474<span id="cb37-10"><a href="#cb37-10" aria-hidden="true"></a><span class="at">#[</span>test<span class="at">]</span></span> 474<span id="cb37-10"><a href="#cb37-10"></a><span class="at">#[</span>test<span class="at">]</span></span>
475<span id="cb37-11"><a href="#cb37-11" aria-hidden="true"></a><span class="kw">fn</span> works() <span class="op">{</span></span> 475<span id="cb37-11"><a href="#cb37-11"></a><span class="kw">fn</span> works() <span class="op">{</span></span>
476<span id="cb37-12"><a href="#cb37-12" aria-hidden="true"></a> <span class="pp">assert_eq!</span>(<span class="dv">15</span><span class="op">,</span> add(<span class="dv">4</span>)(<span class="dv">5</span>)(<span class="dv">6</span>))<span class="op">;</span></span> 476<span id="cb37-12"><a href="#cb37-12"></a> <span class="pp">assert_eq!</span>(<span class="dv">15</span>, add(<span class="dv">4</span>)(<span class="dv">5</span>)(<span class="dv">6</span>));</span>
477<span id="cb37-13"><a href="#cb37-13" aria-hidden="true"></a><span class="op">}</span></span></code></pre></div> 477<span id="cb37-13"><a href="#cb37-13"></a><span class="op">}</span></span></code></pre></div>
478<p>Run <code>cargo +nightly test</code>. You should see a pleasing message:</p> 478<p>Run <code>cargo +nightly test</code>. You should see a pleasing message:</p>
479<pre><code>running 1 test 479<pre><code>running 1 test
480test tests::works ... ok</code></pre> 480test tests::works ... ok</code></pre>
481<p>Take a look at the expansion for our curry macro, via <code>cargo +nightly expand --tests smoke</code>:</p> 481<p>Take a look at the expansion for our curry macro, via <code>cargo +nightly expand --tests smoke</code>:</p>
482<div class="sourceCode" id="cb39"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb39-1"><a href="#cb39-1" aria-hidden="true"></a><span class="kw">type</span> _add_T0 <span class="op">=</span> <span class="dt">u32</span><span class="op">;</span></span> 482<div class="sourceCode" id="cb39"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb39-1"><a href="#cb39-1"></a><span class="kw">type</span> _add_T0 = <span class="dt">u32</span>;</span>
483<span id="cb39-2"><a href="#cb39-2" aria-hidden="true"></a><span class="kw">type</span> _add_T1 <span class="op">=</span> <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) <span class="op">-&gt;</span> _add_T0<span class="op">;</span></span> 483<span id="cb39-2"><a href="#cb39-2"></a><span class="kw">type</span> _add_T1 = <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) -&gt; _add_T0;</span>
484<span id="cb39-3"><a href="#cb39-3" aria-hidden="true"></a><span class="kw">type</span> _add_T2 <span class="op">=</span> <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) <span class="op">-&gt;</span> _add_T1<span class="op">;</span></span> 484<span id="cb39-3"><a href="#cb39-3"></a><span class="kw">type</span> _add_T2 = <span class="kw">impl</span> <span class="bu">Fn</span>(<span class="dt">u32</span>) -&gt; _add_T1;</span>
485<span id="cb39-4"><a href="#cb39-4" aria-hidden="true"></a><span class="kw">fn</span> add(x<span class="op">:</span> <span class="dt">u32</span>) <span class="op">-&gt;</span> _add_T2 <span class="op">{</span></span> 485<span id="cb39-4"><a href="#cb39-4"></a><span class="kw">fn</span> add(x: <span class="dt">u32</span>) -&gt; _add_T2 <span class="op">{</span></span>
486<span id="cb39-5"><a href="#cb39-5" aria-hidden="true"></a> <span class="kw">return</span> (<span class="kw">move</span> <span class="op">|</span>y<span class="op">|</span> <span class="op">{</span></span> 486<span id="cb39-5"><a href="#cb39-5"></a> <span class="kw">return</span> (<span class="kw">move</span> |y| <span class="op">{</span></span>
487<span id="cb39-6"><a href="#cb39-6" aria-hidden="true"></a> <span class="kw">move</span> <span class="op">|</span>z<span class="op">|</span> <span class="op">{</span></span> 487<span id="cb39-6"><a href="#cb39-6"></a> <span class="kw">move</span> |z| <span class="op">{</span></span>
488<span id="cb39-7"><a href="#cb39-7" aria-hidden="true"></a> <span class="kw">return</span> x <span class="op">+</span> y <span class="op">+</span> z<span class="op">;</span></span> 488<span id="cb39-7"><a href="#cb39-7"></a> <span class="kw">return</span> x + y + z;</span>
489<span id="cb39-8"><a href="#cb39-8" aria-hidden="true"></a> <span class="op">}</span></span> 489<span id="cb39-8"><a href="#cb39-8"></a> <span class="op">}</span></span>
490<span id="cb39-9"><a href="#cb39-9" aria-hidden="true"></a> <span class="op">}</span>)<span class="op">;</span></span> 490<span id="cb39-9"><a href="#cb39-9"></a> <span class="op">}</span>);</span>
491<span id="cb39-10"><a href="#cb39-10" aria-hidden="true"></a><span class="op">}</span></span> 491<span id="cb39-10"><a href="#cb39-10"></a><span class="op">}</span></span>
492<span id="cb39-11"><a href="#cb39-11" aria-hidden="true"></a></span> 492<span id="cb39-11"><a href="#cb39-11"></a></span>
493<span id="cb39-12"><a href="#cb39-12" aria-hidden="true"></a><span class="co">// a bunch of other stuff generated by #[test] and assert_eq!</span></span></code></pre></div> 493<span id="cb39-12"><a href="#cb39-12"></a><span class="co">// a bunch of other stuff generated by #[test] and assert_eq!</span></span></code></pre></div>
494<p>A sight for sore eyes.</p> 494<p>A sight for sore eyes.</p>
495<p>Here is a more complex example that generates ten multiples of the first ten natural numbers:</p> 495<p>Here is a more complex example that generates ten multiples of the first ten natural numbers:</p>
496<div class="sourceCode" id="cb40"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb40-1"><a href="#cb40-1" aria-hidden="true"></a><span class="at">#[</span>curry<span class="at">]</span></span> 496<div class="sourceCode" id="cb40"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb40-1"><a href="#cb40-1"></a><span class="at">#[</span>curry<span class="at">]</span></span>
497<span id="cb40-2"><a href="#cb40-2" aria-hidden="true"></a><span class="kw">fn</span> product(x<span class="op">:</span> <span class="dt">u32</span><span class="op">,</span> y<span class="op">:</span> <span class="dt">u32</span>) <span class="op">-&gt;</span> <span class="dt">u32</span> <span class="op">{</span></span> 497<span id="cb40-2"><a href="#cb40-2"></a><span class="kw">fn</span> product(x: <span class="dt">u32</span>, y: <span class="dt">u32</span>) -&gt; <span class="dt">u32</span> <span class="op">{</span></span>
498<span id="cb40-3"><a href="#cb40-3" aria-hidden="true"></a> x <span class="op">*</span> y</span> 498<span id="cb40-3"><a href="#cb40-3"></a> x * y</span>
499<span id="cb40-4"><a href="#cb40-4" aria-hidden="true"></a><span class="op">}</span></span> 499<span id="cb40-4"><a href="#cb40-4"></a><span class="op">}</span></span>
500<span id="cb40-5"><a href="#cb40-5" aria-hidden="true"></a></span> 500<span id="cb40-5"><a href="#cb40-5"></a></span>
501<span id="cb40-6"><a href="#cb40-6" aria-hidden="true"></a><span class="kw">fn</span> multiples() <span class="op">-&gt;</span> <span class="dt">Vec</span><span class="op">&lt;</span><span class="dt">Vec</span><span class="op">&lt;</span><span class="dt">u32</span><span class="op">&gt;&gt;{</span></span> 501<span id="cb40-6"><a href="#cb40-6"></a><span class="kw">fn</span> multiples() -&gt; <span class="dt">Vec</span>&lt;<span class="dt">Vec</span>&lt;<span class="dt">u32</span>&gt;&gt;<span class="op">{</span></span>
502<span id="cb40-7"><a href="#cb40-7" aria-hidden="true"></a> <span class="kw">let</span> v <span class="op">=</span> (<span class="dv">1</span><span class="op">..=</span><span class="dv">10</span>)<span class="op">.</span>map(product)<span class="op">;</span></span> 502<span id="cb40-7"><a href="#cb40-7"></a> <span class="kw">let</span> v = (<span class="dv">1</span>..=<span class="dv">10</span>).map(product);</span>
503<span id="cb40-8"><a href="#cb40-8" aria-hidden="true"></a> <span class="kw">return</span> (<span class="dv">1</span><span class="op">..=</span><span class="dv">10</span>)</span> 503<span id="cb40-8"><a href="#cb40-8"></a> <span class="kw">return</span> (<span class="dv">1</span>..=<span class="dv">10</span>)</span>
504<span id="cb40-9"><a href="#cb40-9" aria-hidden="true"></a> <span class="op">.</span>map(<span class="op">|</span>x<span class="op">|</span> v<span class="op">.</span>clone()<span class="op">.</span>map(<span class="op">|</span>f<span class="op">|</span> f(x))<span class="op">.</span>collect())</span> 504<span id="cb40-9"><a href="#cb40-9"></a> .map(|x| v.clone().map(|f| f(x)).collect())</span>
505<span id="cb40-10"><a href="#cb40-10" aria-hidden="true"></a> <span class="op">.</span>collect()<span class="op">;</span></span> 505<span id="cb40-10"><a href="#cb40-10"></a> .collect();</span>
506<span id="cb40-11"><a href="#cb40-11" aria-hidden="true"></a><span class="op">}</span></span></code></pre></div> 506<span id="cb40-11"><a href="#cb40-11"></a><span class="op">}</span></span></code></pre></div>
507<h3 id="notes">Notes</h3> 507<h3 id="notes">Notes</h3>
508<p>I didn’t quite explain why we use <code>move |arg|</code> in our closure. This is because we want to take ownership of the variable supplied to us. Take a look at this example:</p> 508<p>I didn’t quite explain why we use <code>move |arg|</code> in our closure. This is because we want to take ownership of the variable supplied to us. Take a look at this example:</p>
509<div class="sourceCode" id="cb41"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb41-1"><a href="#cb41-1" aria-hidden="true"></a><span class="kw">let</span> v <span class="op">=</span> add(<span class="dv">5</span>)<span class="op">;</span></span> 509<div class="sourceCode" id="cb41"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb41-1"><a href="#cb41-1"></a><span class="kw">let</span> v = add(<span class="dv">5</span>);</span>
510<span id="cb41-2"><a href="#cb41-2" aria-hidden="true"></a><span class="kw">let</span> g<span class="op">;</span></span> 510<span id="cb41-2"><a href="#cb41-2"></a><span class="kw">let</span> g;</span>
511<span id="cb41-3"><a href="#cb41-3" aria-hidden="true"></a><span class="op">{</span></span> 511<span id="cb41-3"><a href="#cb41-3"></a><span class="op">{</span></span>
512<span id="cb41-4"><a href="#cb41-4" aria-hidden="true"></a> <span class="kw">let</span> x <span class="op">=</span> <span class="dv">5</span><span class="op">;</span></span> 512<span id="cb41-4"><a href="#cb41-4"></a> <span class="kw">let</span> x = <span class="dv">5</span>;</span>
513<span id="cb41-5"><a href="#cb41-5" aria-hidden="true"></a> g <span class="op">=</span> v(x)<span class="op">;</span></span> 513<span id="cb41-5"><a href="#cb41-5"></a> g = v(x);</span>
514<span id="cb41-6"><a href="#cb41-6" aria-hidden="true"></a><span class="op">}</span></span> 514<span id="cb41-6"><a href="#cb41-6"></a><span class="op">}</span></span>
515<span id="cb41-7"><a href="#cb41-7" aria-hidden="true"></a><span class="pp">println!</span>(<span class="st">&quot;{}&quot;</span><span class="op">,</span> g(<span class="dv">2</span>))<span class="op">;</span></span></code></pre></div> 515<span id="cb41-7"><a href="#cb41-7"></a><span class="pp">println!</span>(<span class="st">&quot;{}&quot;</span>, g(<span class="dv">2</span>));</span></code></pre></div>
516<p>Variable <code>x</code> goes out of scope before <code>g</code> can return a concrete value. If we take ownership of <code>x</code> by <code>move</code>ing it into our closure, we can expect this to work reliably. In fact, rustc understands this, and forces you to use <code>move</code>.</p> 516<p>Variable <code>x</code> goes out of scope before <code>g</code> can return a concrete value. If we take ownership of <code>x</code> by <code>move</code>ing it into our closure, we can expect this to work reliably. In fact, rustc understands this, and forces you to use <code>move</code>.</p>
517<p>This usage of <code>move</code> is exactly why <strong>a curried function without a return is useless</strong>. Every variable we pass to our curried function gets moved into its local scope. Playing with these variables cannot cause a change outside this scope. Returning is our only method of interaction with anything beyond this function.</p> 517<p>This usage of <code>move</code> is exactly why <strong>a curried function without a return is useless</strong>. Every variable we pass to our curried function gets moved into its local scope. Playing with these variables cannot cause a change outside this scope. Returning is our only method of interaction with anything beyond this function.</p>
518<h3 id="conclusion">Conclusion</h3> 518<h3 id="conclusion">Conclusion</h3>
diff --git a/docs/posts/get_better_at_yanking_and_putting_in_vim/index.html b/docs/posts/get_better_at_yanking_and_putting_in_vim/index.html
index e02f5d2..5d42ee6 100644
--- a/docs/posts/get_better_at_yanking_and_putting_in_vim/index.html
+++ b/docs/posts/get_better_at_yanking_and_putting_in_vim/index.html
@@ -21,7 +21,7 @@
21">View Raw</a> 21">View Raw</a>
22 <div class="separator"></div> 22 <div class="separator"></div>
23 <div class="date"> 23 <div class="date">
24 29/07 — 2019 24 30/07 — 2019
25 <div class="stats"> 25 <div class="stats">
26 <span class="stats-number"> 26 <span class="stats-number">
27 10.78 27 10.78
diff --git a/docs/posts/gripes_with_go/index.html b/docs/posts/gripes_with_go/index.html
index b527b4a..4d37038 100644
--- a/docs/posts/gripes_with_go/index.html
+++ b/docs/posts/gripes_with_go/index.html
@@ -50,101 +50,101 @@
50<h3 id="lack-of-sum-types">Lack of Sum types</h3> 50<h3 id="lack-of-sum-types">Lack of Sum types</h3>
51<p>A “Sum” type is a data type that can hold one of many states at a given time, similar to how a boolean can hold a true or a false, not too different from an <code>enum</code> type in C. Go lacks <code>enum</code> types unfortunately, and you are forced to resort to crafting your own substitute.</p> 51<p>A “Sum” type is a data type that can hold one of many states at a given time, similar to how a boolean can hold a true or a false, not too different from an <code>enum</code> type in C. Go lacks <code>enum</code> types unfortunately, and you are forced to resort to crafting your own substitute.</p>
52<p>A type to represent gender for example:</p> 52<p>A type to represent gender for example:</p>
53<div class="sourceCode" id="cb1"><pre class="sourceCode go"><code class="sourceCode go"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true"></a><span class="kw">type</span> Gender <span class="dt">int</span></span> 53<div class="sourceCode" id="cb1"><pre class="sourceCode go"><code class="sourceCode go"><span id="cb1-1"><a href="#cb1-1"></a><span class="kw">type</span> Gender <span class="dt">int</span></span>
54<span id="cb1-2"><a href="#cb1-2" aria-hidden="true"></a></span> 54<span id="cb1-2"><a href="#cb1-2"></a></span>
55<span id="cb1-3"><a href="#cb1-3" aria-hidden="true"></a><span class="kw">const</span> (</span> 55<span id="cb1-3"><a href="#cb1-3"></a><span class="kw">const</span> (</span>
56<span id="cb1-4"><a href="#cb1-4" aria-hidden="true"></a> Male Gender = <span class="ot">iota</span> <span class="co">// assigns Male to 0</span></span> 56<span id="cb1-4"><a href="#cb1-4"></a> Male Gender = <span class="ot">iota</span> <span class="co">// assigns Male to 0</span></span>
57<span id="cb1-5"><a href="#cb1-5" aria-hidden="true"></a> Female <span class="co">// assigns Female to 1</span></span> 57<span id="cb1-5"><a href="#cb1-5"></a> Female <span class="co">// assigns Female to 1</span></span>
58<span id="cb1-6"><a href="#cb1-6" aria-hidden="true"></a> Other <span class="co">// assigns Other to 2</span></span> 58<span id="cb1-6"><a href="#cb1-6"></a> Other <span class="co">// assigns Other to 2</span></span>
59<span id="cb1-7"><a href="#cb1-7" aria-hidden="true"></a>)</span> 59<span id="cb1-7"><a href="#cb1-7"></a>)</span>
60<span id="cb1-8"><a href="#cb1-8" aria-hidden="true"></a></span> 60<span id="cb1-8"><a href="#cb1-8"></a></span>
61<span id="cb1-9"><a href="#cb1-9" aria-hidden="true"></a>fmt.Println(<span class="st">&quot;My gender is &quot;</span>, Male)</span> 61<span id="cb1-9"><a href="#cb1-9"></a>fmt.Println(<span class="st">&quot;My gender is &quot;</span>, Male)</span>
62<span id="cb1-10"><a href="#cb1-10" aria-hidden="true"></a><span class="co">// My gender is 0</span></span> 62<span id="cb1-10"><a href="#cb1-10"></a><span class="co">// My gender is 0</span></span>
63<span id="cb1-11"><a href="#cb1-11" aria-hidden="true"></a><span class="co">// Oops! We have to implement String() for Gender ...</span></span> 63<span id="cb1-11"><a href="#cb1-11"></a><span class="co">// Oops! We have to implement String() for Gender ...</span></span>
64<span id="cb1-12"><a href="#cb1-12" aria-hidden="true"></a></span> 64<span id="cb1-12"><a href="#cb1-12"></a></span>
65<span id="cb1-13"><a href="#cb1-13" aria-hidden="true"></a><span class="kw">func</span> (g Gender) String() <span class="dt">string</span> {</span> 65<span id="cb1-13"><a href="#cb1-13"></a><span class="kw">func</span> (g Gender) String() <span class="dt">string</span> {</span>
66<span id="cb1-14"><a href="#cb1-14" aria-hidden="true"></a> <span class="kw">switch</span> (g) {</span> 66<span id="cb1-14"><a href="#cb1-14"></a> <span class="kw">switch</span> (g) {</span>
67<span id="cb1-15"><a href="#cb1-15" aria-hidden="true"></a> <span class="kw">case</span> <span class="dv">0</span>: <span class="kw">return</span> <span class="st">&quot;Male&quot;</span></span> 67<span id="cb1-15"><a href="#cb1-15"></a> <span class="kw">case</span> <span class="dv">0</span>: <span class="kw">return</span> <span class="st">&quot;Male&quot;</span></span>
68<span id="cb1-16"><a href="#cb1-16" aria-hidden="true"></a> <span class="kw">case</span> <span class="dv">1</span>: <span class="kw">return</span> <span class="st">&quot;Female&quot;</span></span> 68<span id="cb1-16"><a href="#cb1-16"></a> <span class="kw">case</span> <span class="dv">1</span>: <span class="kw">return</span> <span class="st">&quot;Female&quot;</span></span>
69<span id="cb1-17"><a href="#cb1-17" aria-hidden="true"></a> <span class="kw">default</span>: <span class="kw">return</span> <span class="st">&quot;Other&quot;</span></span> 69<span id="cb1-17"><a href="#cb1-17"></a> <span class="kw">default</span>: <span class="kw">return</span> <span class="st">&quot;Other&quot;</span></span>
70<span id="cb1-18"><a href="#cb1-18" aria-hidden="true"></a> }</span> 70<span id="cb1-18"><a href="#cb1-18"></a> }</span>
71<span id="cb1-19"><a href="#cb1-19" aria-hidden="true"></a>}</span> 71<span id="cb1-19"><a href="#cb1-19"></a>}</span>
72<span id="cb1-20"><a href="#cb1-20" aria-hidden="true"></a></span> 72<span id="cb1-20"><a href="#cb1-20"></a></span>
73<span id="cb1-21"><a href="#cb1-21" aria-hidden="true"></a><span class="co">// You can accidentally do stupid stuff like:</span></span> 73<span id="cb1-21"><a href="#cb1-21"></a><span class="co">// You can accidentally do stupid stuff like:</span></span>
74<span id="cb1-22"><a href="#cb1-22" aria-hidden="true"></a>gender := Male + <span class="dv">1</span></span></code></pre></div> 74<span id="cb1-22"><a href="#cb1-22"></a>gender := Male + <span class="dv">1</span></span></code></pre></div>
75<p>The Haskell equivalent of the same:</p> 75<p>The Haskell equivalent of the same:</p>
76<div class="sourceCode" id="cb2"><pre class="sourceCode haskell"><code class="sourceCode haskell"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true"></a><span class="kw">data</span> <span class="dt">Gender</span> <span class="ot">=</span> <span class="dt">Male</span></span> 76<div class="sourceCode" id="cb2"><pre class="sourceCode haskell"><code class="sourceCode haskell"><span id="cb2-1"><a href="#cb2-1"></a><span class="kw">data</span> <span class="dt">Gender</span> <span class="ot">=</span> <span class="dt">Male</span></span>
77<span id="cb2-2"><a href="#cb2-2" aria-hidden="true"></a> <span class="op">|</span> <span class="dt">Female</span></span> 77<span id="cb2-2"><a href="#cb2-2"></a> <span class="op">|</span> <span class="dt">Female</span></span>
78<span id="cb2-3"><a href="#cb2-3" aria-hidden="true"></a> <span class="op">|</span> <span class="dt">Other</span></span> 78<span id="cb2-3"><a href="#cb2-3"></a> <span class="op">|</span> <span class="dt">Other</span></span>
79<span id="cb2-4"><a href="#cb2-4" aria-hidden="true"></a> <span class="kw">deriving</span> (<span class="dt">Show</span>)</span> 79<span id="cb2-4"><a href="#cb2-4"></a> <span class="kw">deriving</span> (<span class="dt">Show</span>)</span>
80<span id="cb2-5"><a href="#cb2-5" aria-hidden="true"></a></span> 80<span id="cb2-5"><a href="#cb2-5"></a></span>
81<span id="cb2-6"><a href="#cb2-6" aria-hidden="true"></a><span class="fu">print</span> <span class="op">$</span> <span class="st">&quot;My gender is &quot;</span> <span class="op">++</span> (<span class="fu">show</span> <span class="dt">Male</span>)</span></code></pre></div> 81<span id="cb2-6"><a href="#cb2-6"></a><span class="fu">print</span> <span class="op">$</span> <span class="st">&quot;My gender is &quot;</span> <span class="op">++</span> (<span class="fu">show</span> <span class="dt">Male</span>)</span></code></pre></div>
82<h3 id="type-assertions">Type Assertions</h3> 82<h3 id="type-assertions">Type Assertions</h3>
83<p>A downcast with an optional error check? What could go wrong?</p> 83<p>A downcast with an optional error check? What could go wrong?</p>
84<p>Type assertions in Go allow you to do:</p> 84<p>Type assertions in Go allow you to do:</p>
85<div class="sourceCode" id="cb3"><pre class="sourceCode go"><code class="sourceCode go"><span id="cb3-1"><a href="#cb3-1" aria-hidden="true"></a><span class="kw">var</span> x <span class="kw">interface</span>{} = <span class="dv">7</span></span> 85<div class="sourceCode" id="cb3"><pre class="sourceCode go"><code class="sourceCode go"><span id="cb3-1"><a href="#cb3-1"></a><span class="kw">var</span> x <span class="kw">interface</span>{} = <span class="dv">7</span></span>
86<span id="cb3-2"><a href="#cb3-2" aria-hidden="true"></a>y, goodToGo := x.(<span class="dt">int</span>)</span> 86<span id="cb3-2"><a href="#cb3-2"></a>y, goodToGo := x.(<span class="dt">int</span>)</span>
87<span id="cb3-3"><a href="#cb3-3" aria-hidden="true"></a><span class="kw">if</span> goodToGo {</span> 87<span id="cb3-3"><a href="#cb3-3"></a><span class="kw">if</span> goodToGo {</span>
88<span id="cb3-4"><a href="#cb3-4" aria-hidden="true"></a> fmt.Println(y)</span> 88<span id="cb3-4"><a href="#cb3-4"></a> fmt.Println(y)</span>
89<span id="cb3-5"><a href="#cb3-5" aria-hidden="true"></a>}</span></code></pre></div> 89<span id="cb3-5"><a href="#cb3-5"></a>}</span></code></pre></div>
90<p>The error check however is optional:</p> 90<p>The error check however is optional:</p>
91<div class="sourceCode" id="cb4"><pre class="sourceCode go"><code class="sourceCode go"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true"></a><span class="kw">var</span> x <span class="kw">interface</span>{} = <span class="dv">7</span></span> 91<div class="sourceCode" id="cb4"><pre class="sourceCode go"><code class="sourceCode go"><span id="cb4-1"><a href="#cb4-1"></a><span class="kw">var</span> x <span class="kw">interface</span>{} = <span class="dv">7</span></span>
92<span id="cb4-2"><a href="#cb4-2" aria-hidden="true"></a><span class="kw">var</span> y := x.(<span class="dt">float64</span>)</span> 92<span id="cb4-2"><a href="#cb4-2"></a><span class="kw">var</span> y := x.(<span class="dt">float64</span>)</span>
93<span id="cb4-3"><a href="#cb4-3" aria-hidden="true"></a>fmt.Println(y)</span> 93<span id="cb4-3"><a href="#cb4-3"></a>fmt.Println(y)</span>
94<span id="cb4-4"><a href="#cb4-4" aria-hidden="true"></a><span class="co">// results in a runtime error:</span></span> 94<span id="cb4-4"><a href="#cb4-4"></a><span class="co">// results in a runtime error:</span></span>
95<span id="cb4-5"><a href="#cb4-5" aria-hidden="true"></a><span class="co">// panic: interface conversion: interface {} is int, not float64</span></span></code></pre></div> 95<span id="cb4-5"><a href="#cb4-5"></a><span class="co">// panic: interface conversion: interface {} is int, not float64</span></span></code></pre></div>
96<h3 id="date-and-time">Date and Time</h3> 96<h3 id="date-and-time">Date and Time</h3>
97<p>Anyone that has written Go previously, will probably already know what I am getting at here. For the uninitiated, parsing and formatting dates in Go requires a “layout”. This “layout” is based on magical reference date:</p> 97<p>Anyone that has written Go previously, will probably already know what I am getting at here. For the uninitiated, parsing and formatting dates in Go requires a “layout”. This “layout” is based on magical reference date:</p>
98<pre><code>Mon Jan 2 15:04:05 MST 2006</code></pre> 98<pre><code>Mon Jan 2 15:04:05 MST 2006</code></pre>
99<p>Which is the date produced when you write the first seven natural numbers like so:</p> 99<p>Which is the date produced when you write the first seven natural numbers like so:</p>
100<pre><code>01/02 03:04:05 &#39;06 -0700</code></pre> 100<pre><code>01/02 03:04:05 &#39;06 -0700</code></pre>
101<p>Parsing a string in <code>YYYY-MM-DD</code> format would look something like:</p> 101<p>Parsing a string in <code>YYYY-MM-DD</code> format would look something like:</p>
102<div class="sourceCode" id="cb7"><pre class="sourceCode go"><code class="sourceCode go"><span id="cb7-1"><a href="#cb7-1" aria-hidden="true"></a><span class="kw">const</span> layout = <span class="st">&quot;2006-01-02&quot;</span></span> 102<div class="sourceCode" id="cb7"><pre class="sourceCode go"><code class="sourceCode go"><span id="cb7-1"><a href="#cb7-1"></a><span class="kw">const</span> layout = <span class="st">&quot;2006-01-02&quot;</span></span>
103<span id="cb7-2"><a href="#cb7-2" aria-hidden="true"></a>time.Parse(layout, <span class="st">&quot;2020-08-01&quot;</span>)</span></code></pre></div> 103<span id="cb7-2"><a href="#cb7-2"></a>time.Parse(layout, <span class="st">&quot;2020-08-01&quot;</span>)</span></code></pre></div>
104<p>This so-called “intuitive” method of formatting dates doesn’t allow you to print <code>0000 hrs</code> as <code>2400 hrs</code>, it doesn’t allow you to omit the leading zero in 24 hour formats. It is rife with inconveniences, if only there were a <a href="https://man7.org/linux/man-pages/man3/strftime.3.html">tried and tested</a> date formatting convention …</p> 104<p>This so-called “intuitive” method of formatting dates doesn’t allow you to print <code>0000 hrs</code> as <code>2400 hrs</code>, it doesn’t allow you to omit the leading zero in 24 hour formats. It is rife with inconveniences, if only there were a <a href="https://man7.org/linux/man-pages/man3/strftime.3.html">tried and tested</a> date formatting convention …</p>
105<h3 id="statements-over-expressions">Statements over Expressions</h3> 105<h3 id="statements-over-expressions">Statements over Expressions</h3>
106<p>Statements have side effects, expressions return values. More often than not, expressions are easier to understand at a glance: evaluate the LHS and assign the same to the RHS.</p> 106<p>Statements have side effects, expressions return values. More often than not, expressions are easier to understand at a glance: evaluate the LHS and assign the same to the RHS.</p>
107<p>Rust allows you to create local namespaces, and treats blocks (<code>{}</code>) as expressions:</p> 107<p>Rust allows you to create local namespaces, and treats blocks (<code>{}</code>) as expressions:</p>
108<div class="sourceCode" id="cb8"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb8-1"><a href="#cb8-1" aria-hidden="true"></a><span class="kw">let</span> twenty_seven <span class="op">=</span> <span class="op">{</span></span> 108<div class="sourceCode" id="cb8"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb8-1"><a href="#cb8-1"></a><span class="kw">let</span> twenty_seven = <span class="op">{</span></span>
109<span id="cb8-2"><a href="#cb8-2" aria-hidden="true"></a> <span class="kw">let</span> three <span class="op">=</span> <span class="dv">1</span> <span class="op">+</span> <span class="dv">2</span><span class="op">;</span></span> 109<span id="cb8-2"><a href="#cb8-2"></a> <span class="kw">let</span> three = <span class="dv">1</span> + <span class="dv">2</span>;</span>
110<span id="cb8-3"><a href="#cb8-3" aria-hidden="true"></a> <span class="kw">let</span> nine <span class="op">=</span> three <span class="op">*</span> three<span class="op">;</span></span> 110<span id="cb8-3"><a href="#cb8-3"></a> <span class="kw">let</span> nine = three * three;</span>
111<span id="cb8-4"><a href="#cb8-4" aria-hidden="true"></a> nine <span class="op">*</span> three</span> 111<span id="cb8-4"><a href="#cb8-4"></a> nine * three</span>
112<span id="cb8-5"><a href="#cb8-5" aria-hidden="true"></a><span class="op">};</span></span></code></pre></div> 112<span id="cb8-5"><a href="#cb8-5"></a><span class="op">}</span>;</span></code></pre></div>
113<p>The Go equivalent of the same:</p> 113<p>The Go equivalent of the same:</p>
114<div class="sourceCode" id="cb9"><pre class="sourceCode go"><code class="sourceCode go"><span id="cb9-1"><a href="#cb9-1" aria-hidden="true"></a>twenty_seven := <span class="ot">nil</span></span> 114<div class="sourceCode" id="cb9"><pre class="sourceCode go"><code class="sourceCode go"><span id="cb9-1"><a href="#cb9-1"></a>twenty_seven := <span class="ot">nil</span></span>
115<span id="cb9-2"><a href="#cb9-2" aria-hidden="true"></a></span> 115<span id="cb9-2"><a href="#cb9-2"></a></span>
116<span id="cb9-3"><a href="#cb9-3" aria-hidden="true"></a>three := <span class="dv">1</span> + <span class="dv">2</span></span> 116<span id="cb9-3"><a href="#cb9-3"></a>three := <span class="dv">1</span> + <span class="dv">2</span></span>
117<span id="cb9-4"><a href="#cb9-4" aria-hidden="true"></a>nine := three * three</span> 117<span id="cb9-4"><a href="#cb9-4"></a>nine := three * three</span>
118<span id="cb9-5"><a href="#cb9-5" aria-hidden="true"></a>twenty_seven = nine * three</span></code></pre></div> 118<span id="cb9-5"><a href="#cb9-5"></a>twenty_seven = nine * three</span></code></pre></div>
119<h3 id="erroring-out-on-unused-variables">Erroring out on unused variables</h3> 119<h3 id="erroring-out-on-unused-variables">Erroring out on unused variables</h3>
120<p>Want to quickly prototype something? Go says no! In all seriousness, a warning would suffice, I don’t want to have to go back and comment each unused import out, only to come back and uncomment them a few seconds later.</p> 120<p>Want to quickly prototype something? Go says no! In all seriousness, a warning would suffice, I don’t want to have to go back and comment each unused import out, only to come back and uncomment them a few seconds later.</p>
121<h3 id="error-handling">Error handling</h3> 121<h3 id="error-handling">Error handling</h3>
122<div class="sourceCode" id="cb10"><pre class="sourceCode go"><code class="sourceCode go"><span id="cb10-1"><a href="#cb10-1" aria-hidden="true"></a><span class="kw">if</span> err != <span class="ot">nil</span> { ... }</span></code></pre></div> 122<div class="sourceCode" id="cb10"><pre class="sourceCode go"><code class="sourceCode go"><span id="cb10-1"><a href="#cb10-1"></a><span class="kw">if</span> err != <span class="ot">nil</span> { ... }</span></code></pre></div>
123<p>Need I say more? I will, for good measure:</p> 123<p>Need I say more? I will, for good measure:</p>
124<ol type="1"> 124<ol type="1">
125<li>Error handling is optional</li> 125<li>Error handling is optional</li>
126<li>Errors are propagated via a clunky <code>if</code> + <code>return</code> statement</li> 126<li>Errors are propagated via a clunky <code>if</code> + <code>return</code> statement</li>
127</ol> 127</ol>
128<p>I prefer Haskell’s “Monadic” error handling, which is employed by Rust as well:</p> 128<p>I prefer Haskell’s “Monadic” error handling, which is employed by Rust as well:</p>
129<div class="sourceCode" id="cb11"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb11-1"><a href="#cb11-1" aria-hidden="true"></a><span class="co">// 1. error handling is compulsory</span></span> 129<div class="sourceCode" id="cb11"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb11-1"><a href="#cb11-1"></a><span class="co">// 1. error handling is compulsory</span></span>
130<span id="cb11-2"><a href="#cb11-2" aria-hidden="true"></a><span class="co">// 2. errors are propagated with the `?` operator</span></span> 130<span id="cb11-2"><a href="#cb11-2"></a><span class="co">// 2. errors are propagated with the `?` operator</span></span>
131<span id="cb11-3"><a href="#cb11-3" aria-hidden="true"></a><span class="kw">fn</span> foo() <span class="op">-&gt;</span> <span class="dt">Result</span><span class="op">&lt;</span><span class="dt">String</span><span class="op">,</span> <span class="pp">io::</span><span class="bu">Error</span><span class="op">&gt;</span> <span class="op">{</span></span> 131<span id="cb11-3"><a href="#cb11-3"></a><span class="kw">fn</span> foo() -&gt; <span class="dt">Result</span>&lt;<span class="dt">String</span>, <span class="pp">io::</span>Error&gt; <span class="op">{</span></span>
132<span id="cb11-4"><a href="#cb11-4" aria-hidden="true"></a> <span class="kw">let</span> <span class="kw">mut</span> f <span class="op">=</span> <span class="pp">File::</span>open(<span class="st">&quot;foo.txt&quot;</span>)<span class="op">?;</span> <span class="co">// return if error</span></span> 132<span id="cb11-4"><a href="#cb11-4"></a> <span class="kw">let</span> <span class="kw">mut</span> f = <span class="pp">File::</span>open(<span class="st">&quot;foo.txt&quot;</span>)?; <span class="co">// return if error</span></span>
133<span id="cb11-5"><a href="#cb11-5" aria-hidden="true"></a> <span class="kw">let</span> <span class="kw">mut</span> s <span class="op">=</span> <span class="dt">String</span><span class="pp">::</span>new()<span class="op">;</span></span> 133<span id="cb11-5"><a href="#cb11-5"></a> <span class="kw">let</span> <span class="kw">mut</span> s = <span class="dt">String</span>::new();</span>
134<span id="cb11-6"><a href="#cb11-6" aria-hidden="true"></a></span> 134<span id="cb11-6"><a href="#cb11-6"></a></span>
135<span id="cb11-7"><a href="#cb11-7" aria-hidden="true"></a> f<span class="op">.</span>read_to_string(<span class="op">&amp;</span><span class="kw">mut</span> s)<span class="op">?;</span> <span class="co">// return if error</span></span> 135<span id="cb11-7"><a href="#cb11-7"></a> f.read_to_string(&amp;<span class="kw">mut</span> s)?; <span class="co">// return if error</span></span>
136<span id="cb11-8"><a href="#cb11-8" aria-hidden="true"></a></span> 136<span id="cb11-8"><a href="#cb11-8"></a></span>
137<span id="cb11-9"><a href="#cb11-9" aria-hidden="true"></a> <span class="cn">Ok</span>(s) <span class="co">// all good, return a string inside a `Result` context</span></span> 137<span id="cb11-9"><a href="#cb11-9"></a> <span class="cn">Ok</span>(s) <span class="co">// all good, return a string inside a `Result` context</span></span>
138<span id="cb11-10"><a href="#cb11-10" aria-hidden="true"></a><span class="op">}</span></span> 138<span id="cb11-10"><a href="#cb11-10"></a><span class="op">}</span></span>
139<span id="cb11-11"><a href="#cb11-11" aria-hidden="true"></a></span> 139<span id="cb11-11"><a href="#cb11-11"></a></span>
140<span id="cb11-12"><a href="#cb11-12" aria-hidden="true"></a><span class="kw">fn</span> main() <span class="op">{</span></span> 140<span id="cb11-12"><a href="#cb11-12"></a><span class="kw">fn</span> main() <span class="op">{</span></span>
141<span id="cb11-13"><a href="#cb11-13" aria-hidden="true"></a> <span class="co">// `contents` is an enum known as Result:</span></span> 141<span id="cb11-13"><a href="#cb11-13"></a> <span class="co">// `contents` is an enum known as Result:</span></span>
142<span id="cb11-14"><a href="#cb11-14" aria-hidden="true"></a> <span class="kw">let</span> contents <span class="op">=</span> foo()<span class="op">;</span></span> 142<span id="cb11-14"><a href="#cb11-14"></a> <span class="kw">let</span> contents = foo();</span>
143<span id="cb11-15"><a href="#cb11-15" aria-hidden="true"></a> <span class="kw">match</span> contents <span class="op">{</span></span> 143<span id="cb11-15"><a href="#cb11-15"></a> <span class="kw">match</span> contents <span class="op">{</span></span>
144<span id="cb11-16"><a href="#cb11-16" aria-hidden="true"></a> <span class="cn">Ok</span>(c) <span class="op">=&gt;</span> <span class="pp">println!</span>(c)<span class="op">,</span></span> 144<span id="cb11-16"><a href="#cb11-16"></a> <span class="cn">Ok</span>(c) =&gt; <span class="pp">println!</span>(c),</span>
145<span id="cb11-17"><a href="#cb11-17" aria-hidden="true"></a> <span class="cn">Err</span>(e) <span class="op">=&gt;</span> <span class="pp">eprintln!</span>(e)</span> 145<span id="cb11-17"><a href="#cb11-17"></a> <span class="cn">Err</span>(e) =&gt; <span class="pp">eprintln!</span>(e)</span>
146<span id="cb11-18"><a href="#cb11-18" aria-hidden="true"></a> <span class="op">}</span></span> 146<span id="cb11-18"><a href="#cb11-18"></a> <span class="op">}</span></span>
147<span id="cb11-19"><a href="#cb11-19" aria-hidden="true"></a><span class="op">}</span></span></code></pre></div> 147<span id="cb11-19"><a href="#cb11-19"></a><span class="op">}</span></span></code></pre></div>
148<h3 id="conclusion">Conclusion</h3> 148<h3 id="conclusion">Conclusion</h3>
149<p>I did not want to conclude without talking about stylistic choices, lack of metaprogramming, bizzare export rules, but, I am too busy converting my <code>interface{}</code> types into actual generic code for Go v2.</p> 149<p>I did not want to conclude without talking about stylistic choices, lack of metaprogramming, bizzare export rules, but, I am too busy converting my <code>interface{}</code> types into actual generic code for Go v2.</p>
150 150
diff --git a/docs/posts/nixOS/index.html b/docs/posts/nixOS/index.html
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24 01/09 — 2020
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37 <h1>
38 NixOS
39 </h1>
40 <div class="post-text">
41 <p>I have been eyeing operating systems with functional package managers for a while now, aka, NixOS or Guix. Reproducible builds, declarative and rollback-able system configuration, system consistency, all sound pretty cool. I have been using NixOS for about a month now.</p>
42<h3 id="installation">Installation</h3>
43<p>I went with their minimal installation ISO. The installation was pretty smooth from start to end, no hitches there. The entire <a href="https://nixos.org/manual/nixos/stable/">manual</a> is available offline, and is accessible during the installation. Very handy.</p>
44<h3 id="setup">Setup</h3>
45<p>The entire system is configured via <code>/etc/nixos/configuration.nix</code>. Wifi, <code>libinput</code> gestures, audio, locale settings, there are options for literally everything. You can declaratively write down the packages you want installed too. With fresh installs of most distros, I usually fumble with getting things like screen backlight and media keys to work. If I do manage to fix it, I can’t carry it forward to future installations trivially. Getting all my hardware to work on NixOS is as easy as:</p>
46<pre><code>{
47 server.xserver.libinput.enable = true; # touchpad
48 programs.light.enable = true; # backlight
49 hardware.pulseaudio.enable = true; # audio
50 networking.wireless.enable = true; # wifi
51}</code></pre>
52<h3 id="developing-with-nix">Developing with Nix</h3>
53<p>Nix makes it easy to enter environments that aren’t affected by your system configuration using <code>nix-shell</code>.</p>
54<p>Builds may be generated by specifying a <code>default.nix</code> file, and running <code>nix-build</code>. Conventional package managers require you to specify a dependency list, but there is no guarantee that this list is complete. The package will build on your machine even if you forget a dependency. However, with Nix, packages are installed to <code>/nix/store</code>, and not global paths such as <code>/usr/bin/...</code>, if your project builds, it means you have included every last one.</p>
55<p>Issues on most my projects have been “unable to build because <code>libxcb</code> is missing”, or “this version of <code>openssl</code> is too old”. Tools like <code>cargo</code> and <code>pip</code> are poor package managers. While they <em>can</em> guarantee that Rust or Python dependencies are met, they make assumptions about the target system.</p>
56<p>For example, <a href="https://github.com/nerdypepper/site">this website</a> is now built using Nix, anyone using Nix may simply, clone the repository and run <code>./generate.sh</code>, and it would <em>just work</em>, while keeping your global namespace clean™:</p>
57<div class="sourceCode" id="cb2"><pre class="sourceCode bash"><code class="sourceCode bash"><span id="cb2-1"><a href="#cb2-1"></a><span class="co">#! /usr/bin/env nix-shell</span></span>
58<span id="cb2-2"><a href="#cb2-2"></a><span class="co">#! nix-shell -i bash -p eva pandoc esh</span></span>
59<span id="cb2-3"><a href="#cb2-3"></a></span>
60<span id="cb2-4"><a href="#cb2-4"></a><span class="co"># some bash magic ;)</span></span></code></pre></div>
61<p>Dependencies are included with the <code>-p</code> flag, the shell script is executed with an interpreter, specified with the <code>-i</code> flag.</p>
62<h3 id="impressions">Impressions</h3>
63<p>NixOS is by no means, simple. As a newcomer, using Nix was not easy, heck, I had to learn a purely functional, lazy language to just build programs. There is a lot to be desired on the tooling front as well. A well fleshed out LSP plugin would be nice (<a href="https://github.com/nix-community/rnix-lsp">rnix-lsp looks promising</a>).</p>
64<p>Being able to rollback changes at a system level is cool. Package broke something? Just <code>nixos-rebuild switch --rollback</code>! Deleted <code>nix</code> by mistake? Find the binary in <code>/nix/store</code> and rollback! You aren’t punished for not thinking twice.</p>
65<p>I don’t see myself switching to anything else in the near future, NixOS does a lot of things right. If I ever need to reinstall NixOS, I can generate an <a href="https://github.com/nix-community/nixos-generators">image of my current system</a>.</p>
66<p><a href="https://u.peppe.rs/6m.png"><img src="https://u.peppe.rs/6m.png" /></a></p>
67
68 </div>
69
70 <div class=intro>
71 Hi.
72 <div class=hot-links>
73 <a href=https://peppe.rs/index.xml class=feed-button>Subscribe</a>
74 <a href=https://liberapay.com/nerdypepper/donate class=donate-button>Donate</a>
75 </div>
76 <p>I'm Akshay, I go by nerd or nerdypepper on the internet.</p>
77 <p>
78 I am a compsci undergrad, Rust programmer and an enthusiastic Vimmer.
79 I write open-source stuff to pass time. I also design fonts: scientifica, curie.
80 </p>
81 <p>Send me a mail at [email protected] or a message at [email protected].</p>
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diff --git a/docs/posts/rapid_refactoring_with_vim/index.html b/docs/posts/rapid_refactoring_with_vim/index.html
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40 <div class="post-text"> 40 <div class="post-text">
41 <p>Last weekend, I was tasked with refactoring the 96 unit tests on <a href="https://github.com/ruma/ruma-events/pull/70">ruma-events</a> to use strictly typed json objects using <code>serde_json::json!</code> instead of raw strings. It was rather painless thanks to vim :)</p> 41 <p>Last weekend, I was tasked with refactoring the 96 unit tests on <a href="https://github.com/ruma/ruma-events/pull/70">ruma-events</a> to use strictly typed json objects using <code>serde_json::json!</code> instead of raw strings. It was rather painless thanks to vim :)</p>
42<p>Here’s a small sample of what had to be done (note the lines prefixed with the arrow):</p> 42<p>Here’s a small sample of what had to be done (note the lines prefixed with the arrow):</p>
43<div class="sourceCode" id="cb1"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true"></a>→ <span class="kw">use</span> <span class="pp">serde_json::</span><span class="op">{</span>from_str<span class="op">};</span></span> 43<div class="sourceCode" id="cb1"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb1-1"><a href="#cb1-1"></a>→ <span class="kw">use</span> <span class="pp">serde_json::</span><span class="op">{</span>from_str<span class="op">}</span>;</span>
44<span id="cb1-2"><a href="#cb1-2" aria-hidden="true"></a> </span> 44<span id="cb1-2"><a href="#cb1-2"></a> </span>
45<span id="cb1-3"><a href="#cb1-3" aria-hidden="true"></a> <span class="at">#[</span>test<span class="at">]</span></span> 45<span id="cb1-3"><a href="#cb1-3"></a> <span class="at">#[</span>test<span class="at">]</span></span>
46<span id="cb1-4"><a href="#cb1-4" aria-hidden="true"></a> <span class="kw">fn</span> deserialize() <span class="op">{</span></span> 46<span id="cb1-4"><a href="#cb1-4"></a> <span class="kw">fn</span> deserialize() <span class="op">{</span></span>
47<span id="cb1-5"><a href="#cb1-5" aria-hidden="true"></a> <span class="pp">assert_eq!</span>(</span> 47<span id="cb1-5"><a href="#cb1-5"></a> <span class="pp">assert_eq!</span>(</span>
48<span id="cb1-6"><a href="#cb1-6" aria-hidden="true"></a>→ <span class="pp">from_str::</span><span class="op">&lt;</span>Action<span class="op">&gt;</span>(<span class="st">r#&quot;{&quot;set_tweak&quot;: &quot;highlight&quot;}&quot;#),</span></span> 48<span id="cb1-6"><a href="#cb1-6"></a>→ <span class="pp">from_str::</span>&lt;Action&gt;(<span class="st">r#&quot;{&quot;set_tweak&quot;: &quot;highlight&quot;}&quot;#</span>),</span>
49<span id="cb1-7"><a href="#cb1-7" aria-hidden="true"></a><span class="st"> Action::SetTweak(Tweak::Highlight { value: true })</span></span> 49<span id="cb1-7"><a href="#cb1-7"></a> <span class="pp">Action::</span>SetTweak(<span class="pp">Tweak::</span>Highlight <span class="op">{</span> value: <span class="cn">true</span> <span class="op">}</span>)</span>
50<span id="cb1-8"><a href="#cb1-8" aria-hidden="true"></a><span class="st"> );</span></span> 50<span id="cb1-8"><a href="#cb1-8"></a> );</span>
51<span id="cb1-9"><a href="#cb1-9" aria-hidden="true"></a><span class="st"> }</span></span></code></pre></div> 51<span id="cb1-9"><a href="#cb1-9"></a> <span class="op">}</span></span></code></pre></div>
52<p>had to be converted to:</p> 52<p>had to be converted to:</p>
53<div class="sourceCode" id="cb2"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true"></a>→ <span class="kw">use</span> <span class="pp">serde_json::</span><span class="op">{</span>from_value<span class="op">};</span></span> 53<div class="sourceCode" id="cb2"><pre class="sourceCode rust"><code class="sourceCode rust"><span id="cb2-1"><a href="#cb2-1"></a>→ <span class="kw">use</span> <span class="pp">serde_json::</span><span class="op">{</span>from_value<span class="op">}</span>;</span>
54<span id="cb2-2"><a href="#cb2-2" aria-hidden="true"></a> </span> 54<span id="cb2-2"><a href="#cb2-2"></a> </span>
55<span id="cb2-3"><a href="#cb2-3" aria-hidden="true"></a> <span class="at">#[</span>test<span class="at">]</span></span> 55<span id="cb2-3"><a href="#cb2-3"></a> <span class="at">#[</span>test<span class="at">]</span></span>
56<span id="cb2-4"><a href="#cb2-4" aria-hidden="true"></a> <span class="kw">fn</span> deserialize() <span class="op">{</span></span> 56<span id="cb2-4"><a href="#cb2-4"></a> <span class="kw">fn</span> deserialize() <span class="op">{</span></span>
57<span id="cb2-5"><a href="#cb2-5" aria-hidden="true"></a> <span class="pp">assert_eq!</span>(</span> 57<span id="cb2-5"><a href="#cb2-5"></a> <span class="pp">assert_eq!</span>(</span>
58<span id="cb2-6"><a href="#cb2-6" aria-hidden="true"></a>→ <span class="pp">from_value::</span><span class="op">&lt;</span>Action<span class="op">&gt;</span>(<span class="pp">json!</span>(<span class="op">{</span><span class="st">&quot;set_tweak&quot;</span><span class="op">:</span> <span class="st">&quot;highlight&quot;</span><span class="op">}</span>))<span class="op">,</span></span> 58<span id="cb2-6"><a href="#cb2-6"></a>→ <span class="pp">from_value::</span>&lt;Action&gt;(<span class="pp">json!</span>(<span class="op">{</span><span class="st">&quot;set_tweak&quot;</span>: <span class="st">&quot;highlight&quot;</span><span class="op">}</span>)),</span>
59<span id="cb2-7"><a href="#cb2-7" aria-hidden="true"></a> <span class="pp">Action::</span>SetTweak(<span class="pp">Tweak::</span>Highlight <span class="op">{</span> value<span class="op">:</span> <span class="cn">true</span> <span class="op">}</span>)</span> 59<span id="cb2-7"><a href="#cb2-7"></a> <span class="pp">Action::</span>SetTweak(<span class="pp">Tweak::</span>Highlight <span class="op">{</span> value: <span class="cn">true</span> <span class="op">}</span>)</span>
60<span id="cb2-8"><a href="#cb2-8" aria-hidden="true"></a> )<span class="op">;</span></span> 60<span id="cb2-8"><a href="#cb2-8"></a> );</span>
61<span id="cb2-9"><a href="#cb2-9" aria-hidden="true"></a> <span class="op">}</span></span></code></pre></div> 61<span id="cb2-9"><a href="#cb2-9"></a> <span class="op">}</span></span></code></pre></div>
62<h3 id="the-arglist">The arglist</h3> 62<h3 id="the-arglist">The arglist</h3>
63<p>For the initial pass, I decided to handle imports, this was a simple find and replace operation, done to all the files containing tests. Luckily, modules (and therefore files) containing tests in Rust are annotated with the <code>#[cfg(test)]</code> attribute. I opened all such files:</p> 63<p>For the initial pass, I decided to handle imports, this was a simple find and replace operation, done to all the files containing tests. Luckily, modules (and therefore files) containing tests in Rust are annotated with the <code>#[cfg(test)]</code> attribute. I opened all such files:</p>
64<div class="sourceCode" id="cb3"><pre class="sourceCode bash"><code class="sourceCode bash"><span id="cb3-1"><a href="#cb3-1" aria-hidden="true"></a><span class="co"># `grep -l pattern files` lists all the files</span></span> 64<div class="sourceCode" id="cb3"><pre class="sourceCode bash"><code class="sourceCode bash"><span id="cb3-1"><a href="#cb3-1"></a><span class="co"># `grep -l pattern files` lists all the files</span></span>
65<span id="cb3-2"><a href="#cb3-2" aria-hidden="true"></a><span class="co"># matching the pattern</span></span> 65<span id="cb3-2"><a href="#cb3-2"></a><span class="co"># matching the pattern</span></span>
66<span id="cb3-3"><a href="#cb3-3" aria-hidden="true"></a></span> 66<span id="cb3-3"><a href="#cb3-3"></a></span>
67<span id="cb3-4"><a href="#cb3-4" aria-hidden="true"></a><span class="ex">vim</span> <span class="va">$(</span><span class="fu">grep</span> -l <span class="st">&#39;cfg\(test\)&#39;</span> ./**/*.rs<span class="va">)</span></span> 67<span id="cb3-4"><a href="#cb3-4"></a><span class="ex">vim</span> <span class="va">$(</span><span class="fu">grep</span> -l <span class="st">&#39;cfg\(test\)&#39;</span> ./**/*.rs<span class="va">)</span></span>
68<span id="cb3-5"><a href="#cb3-5" aria-hidden="true"></a></span> 68<span id="cb3-5"><a href="#cb3-5"></a></span>
69<span id="cb3-6"><a href="#cb3-6" aria-hidden="true"></a><span class="co"># expands to something like:</span></span> 69<span id="cb3-6"><a href="#cb3-6"></a><span class="co"># expands to something like:</span></span>
70<span id="cb3-7"><a href="#cb3-7" aria-hidden="true"></a><span class="ex">vim</span> push_rules.rs room/member.rs key/verification/lib.rs</span></code></pre></div> 70<span id="cb3-7"><a href="#cb3-7"></a><span class="ex">vim</span> push_rules.rs room/member.rs key/verification/lib.rs</span></code></pre></div>
71<p>Starting vim with more than one file at the shell prompt populates the arglist. Hit <code>:args</code> to see the list of files currently ready to edit. The square [brackets] indicate the current file. Navigate through the arglist with <code>:next</code> and <code>:prev</code>. I use tpope’s vim-unimpaired <a href="#fn1" class="footnote-ref" id="fnref1" role="doc-noteref"><sup>1</sup></a>, which adds <code>]a</code> and <code>[a</code>, mapped to <code>:next</code> and <code>:prev</code>.</p> 71<p>Starting vim with more than one file at the shell prompt populates the arglist. Hit <code>:args</code> to see the list of files currently ready to edit. The square [brackets] indicate the current file. Navigate through the arglist with <code>:next</code> and <code>:prev</code>. I use tpope’s vim-unimpaired <a href="#fn1" class="footnote-ref" id="fnref1" role="doc-noteref"><sup>1</sup></a>, which adds <code>]a</code> and <code>[a</code>, mapped to <code>:next</code> and <code>:prev</code>.</p>
72<p>All that’s left to do is the find and replace, for which we will be using vim’s <code>argdo</code>, applying a substitution to every file in the arglist:</p> 72<p>All that’s left to do is the find and replace, for which we will be using vim’s <code>argdo</code>, applying a substitution to every file in the arglist:</p>
73<pre><code>:argdo s/from_str/from_value/g</code></pre> 73<pre><code>:argdo s/from_str/from_value/g</code></pre>
diff --git a/docs/posts/static_sites_with_bash/index.html b/docs/posts/static_sites_with_bash/index.html
index 80bfe37..86e4a12 100644
--- a/docs/posts/static_sites_with_bash/index.html
+++ b/docs/posts/static_sites_with_bash/index.html
@@ -43,26 +43,26 @@
43<p>I chose to write in markdown, and convert to html with <a href="https://kristaps.bsd.lv/lowdown/">lowdown</a>.</p> 43<p>I chose to write in markdown, and convert to html with <a href="https://kristaps.bsd.lv/lowdown/">lowdown</a>.</p>
44<h3 id="directory-structure">Directory structure</h3> 44<h3 id="directory-structure">Directory structure</h3>
45<p>I host my site on GitHub pages, so <code>docs/</code> has to be the entry point. Markdown formatted posts go into <code>posts/</code>, get converted into html, and end up in <code>docs/index.html</code>, something like this:</p> 45<p>I host my site on GitHub pages, so <code>docs/</code> has to be the entry point. Markdown formatted posts go into <code>posts/</code>, get converted into html, and end up in <code>docs/index.html</code>, something like this:</p>
46<div class="sourceCode" id="cb1"><pre class="sourceCode bash"><code class="sourceCode bash"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true"></a><span class="va">posts=$(</span><span class="fu">ls</span> -t ./posts<span class="va">)</span> <span class="co"># chronological order!</span></span> 46<div class="sourceCode" id="cb1"><pre class="sourceCode bash"><code class="sourceCode bash"><span id="cb1-1"><a href="#cb1-1"></a><span class="va">posts=$(</span><span class="fu">ls</span> -t ./posts<span class="va">)</span> <span class="co"># chronological order!</span></span>
47<span id="cb1-2"><a href="#cb1-2" aria-hidden="true"></a><span class="kw">for</span> <span class="ex">f</span> in <span class="va">$posts</span><span class="kw">;</span> <span class="kw">do</span></span> 47<span id="cb1-2"><a href="#cb1-2"></a><span class="kw">for</span> <span class="ex">f</span> in <span class="va">$posts</span><span class="kw">;</span> <span class="kw">do</span></span>
48<span id="cb1-3"><a href="#cb1-3" aria-hidden="true"></a> <span class="va">file=</span><span class="st">&quot;./posts/&quot;</span><span class="va">$f</span> <span class="co"># `ls` mangled our file paths</span></span> 48<span id="cb1-3"><a href="#cb1-3"></a> <span class="va">file=</span><span class="st">&quot;./posts/&quot;</span><span class="va">$f</span> <span class="co"># `ls` mangled our file paths</span></span>
49<span id="cb1-4"><a href="#cb1-4" aria-hidden="true"></a> <span class="bu">echo</span> <span class="st">&quot;generating post </span><span class="va">$file</span><span class="st">&quot;</span></span> 49<span id="cb1-4"><a href="#cb1-4"></a> <span class="bu">echo</span> <span class="st">&quot;generating post </span><span class="va">$file</span><span class="st">&quot;</span></span>
50<span id="cb1-5"><a href="#cb1-5" aria-hidden="true"></a></span> 50<span id="cb1-5"><a href="#cb1-5"></a></span>
51<span id="cb1-6"><a href="#cb1-6" aria-hidden="true"></a> <span class="va">html=$(</span><span class="ex">lowdown</span> <span class="st">&quot;</span><span class="va">$file</span><span class="st">&quot;</span><span class="va">)</span></span> 51<span id="cb1-6"><a href="#cb1-6"></a> <span class="va">html=$(</span><span class="ex">lowdown</span> <span class="st">&quot;</span><span class="va">$file</span><span class="st">&quot;</span><span class="va">)</span></span>
52<span id="cb1-7"><a href="#cb1-7" aria-hidden="true"></a> <span class="bu">echo</span> -e <span class="st">&quot;html&quot;</span> <span class="op">&gt;&gt;</span> docs/index.html</span> 52<span id="cb1-7"><a href="#cb1-7"></a> <span class="bu">echo</span> -e <span class="st">&quot;html&quot;</span> <span class="op">&gt;&gt;</span> docs/index.html</span>
53<span id="cb1-8"><a href="#cb1-8" aria-hidden="true"></a><span class="kw">done</span></span></code></pre></div> 53<span id="cb1-8"><a href="#cb1-8"></a><span class="kw">done</span></span></code></pre></div>
54<h3 id="assets">Assets</h3> 54<h3 id="assets">Assets</h3>
55<p>Most static site generators recommend dropping image assets into the site source itself. That does have it’s merits, but I prefer hosting images separately:</p> 55<p>Most static site generators recommend dropping image assets into the site source itself. That does have it’s merits, but I prefer hosting images separately:</p>
56<div class="sourceCode" id="cb2"><pre class="sourceCode bash"><code class="sourceCode bash"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true"></a><span class="co"># strip file extension</span></span> 56<div class="sourceCode" id="cb2"><pre class="sourceCode bash"><code class="sourceCode bash"><span id="cb2-1"><a href="#cb2-1"></a><span class="co"># strip file extension</span></span>
57<span id="cb2-2"><a href="#cb2-2" aria-hidden="true"></a><span class="va">ext=</span><span class="st">&quot;</span><span class="va">${1##</span>*.<span class="va">}</span><span class="st">&quot;</span></span> 57<span id="cb2-2"><a href="#cb2-2"></a><span class="va">ext=</span><span class="st">&quot;</span><span class="va">${1##</span>*.<span class="va">}</span><span class="st">&quot;</span></span>
58<span id="cb2-3"><a href="#cb2-3" aria-hidden="true"></a></span> 58<span id="cb2-3"><a href="#cb2-3"></a></span>
59<span id="cb2-4"><a href="#cb2-4" aria-hidden="true"></a><span class="co"># generate a random file name</span></span> 59<span id="cb2-4"><a href="#cb2-4"></a><span class="co"># generate a random file name</span></span>
60<span id="cb2-5"><a href="#cb2-5" aria-hidden="true"></a><span class="va">id=$(</span> <span class="fu">cat</span> /dev/urandom <span class="kw">|</span> <span class="fu">tr</span> -dc <span class="st">&#39;a-zA-Z0-9&#39;</span> <span class="kw">|</span> <span class="ex">fold</span> -w 2 <span class="kw">|</span> <span class="fu">head</span> -n 1 <span class="va">)</span></span> 60<span id="cb2-5"><a href="#cb2-5"></a><span class="va">id=$(</span> <span class="fu">cat</span> /dev/urandom <span class="kw">|</span> <span class="fu">tr</span> -dc <span class="st">&#39;a-zA-Z0-9&#39;</span> <span class="kw">|</span> <span class="ex">fold</span> -w 2 <span class="kw">|</span> <span class="fu">head</span> -n 1 <span class="va">)</span></span>
61<span id="cb2-6"><a href="#cb2-6" aria-hidden="true"></a><span class="va">id=</span><span class="st">&quot;</span><span class="va">$id</span><span class="st">.</span><span class="va">$ext</span><span class="st">&quot;</span></span> 61<span id="cb2-6"><a href="#cb2-6"></a><span class="va">id=</span><span class="st">&quot;</span><span class="va">$id</span><span class="st">.</span><span class="va">$ext</span><span class="st">&quot;</span></span>
62<span id="cb2-7"><a href="#cb2-7" aria-hidden="true"></a></span> 62<span id="cb2-7"><a href="#cb2-7"></a></span>
63<span id="cb2-8"><a href="#cb2-8" aria-hidden="true"></a><span class="co"># copy to my file host</span></span> 63<span id="cb2-8"><a href="#cb2-8"></a><span class="co"># copy to my file host</span></span>
64<span id="cb2-9"><a href="#cb2-9" aria-hidden="true"></a><span class="fu">scp</span> -P 443 <span class="st">&quot;</span><span class="va">$1</span><span class="st">&quot;</span> emerald:files/<span class="st">&quot;</span><span class="va">$id</span><span class="st">&quot;</span> </span> 64<span id="cb2-9"><a href="#cb2-9"></a><span class="fu">scp</span> -P 443 <span class="st">&quot;</span><span class="va">$1</span><span class="st">&quot;</span> emerald:files/<span class="st">&quot;</span><span class="va">$id</span><span class="st">&quot;</span> </span>
65<span id="cb2-10"><a href="#cb2-10" aria-hidden="true"></a><span class="bu">echo</span> <span class="st">&quot;https://u.peppe.rs/</span><span class="va">$id</span><span class="st">&quot;</span></span></code></pre></div> 65<span id="cb2-10"><a href="#cb2-10"></a><span class="bu">echo</span> <span class="st">&quot;https://u.peppe.rs/</span><span class="va">$id</span><span class="st">&quot;</span></span></code></pre></div>
66<h3 id="templating">Templating</h3> 66<h3 id="templating">Templating</h3>
67<p><a href="https://github.com/NerdyPepper/site/blob/master/generate.sh"><code>generate.sh</code></a> brings the above bits and pieces together (with some extra cruft to avoid javascript). It uses <code>sed</code> to produce nice titles from the file names (removes underscores, title-case), and <code>date(1)</code> to add the date to each post listing!</p> 67<p><a href="https://github.com/NerdyPepper/site/blob/master/generate.sh"><code>generate.sh</code></a> brings the above bits and pieces together (with some extra cruft to avoid javascript). It uses <code>sed</code> to produce nice titles from the file names (removes underscores, title-case), and <code>date(1)</code> to add the date to each post listing!</p>
68 68
diff --git a/generate.sh b/generate.sh
index 86a5a40..0495d42 100755
--- a/generate.sh
+++ b/generate.sh
@@ -1,5 +1,5 @@
1#! /usr/bin/env bash 1#! /usr/bin/env nix-shell
2 2#! nix-shell -i bash -p eva pandoc esh
3 3
4title_wrapper() { 4title_wrapper() {
5 # remove extension 5 # remove extension
@@ -110,7 +110,7 @@ for f in $posts; do
110 110
111 id="${id%.*}" 111 id="${id%.*}"
112 mkdir -p "docs/posts/$id" 112 mkdir -p "docs/posts/$id"
113 esh -s /bin/bash \ 113 esh \
114 -o "docs/posts/$id/index.html" \ 114 -o "docs/posts/$id/index.html" \
115 "./post.esh" \ 115 "./post.esh" \
116 file="$file" \ 116 file="$file" \
@@ -123,7 +123,7 @@ done
123 123
124# generate rss feeds 124# generate rss feeds
125echo "generating RSS feeds ..." 125echo "generating RSS feeds ..."
126esh -s /bin/bash \ 126esh \
127 -o "./docs/index.xml" \ 127 -o "./docs/index.xml" \
128 "rss.esh" 128 "rss.esh"
129 129
diff --git a/posts/nixOS.md b/posts/nixOS.md
new file mode 100644
index 0000000..7e91f93
--- /dev/null
+++ b/posts/nixOS.md
@@ -0,0 +1,94 @@
1I have been eyeing operating systems with functional package
2managers for a while now, aka, NixOS or Guix. Reproducible
3builds, declarative and rollback-able system configuration,
4system consistency, all sound pretty cool. I have been using
5NixOS for about a month now.
6
7### Installation
8
9I went with their minimal installation ISO. The installation
10was pretty smooth from start to end, no hitches there. The
11entire [manual](https://nixos.org/manual/nixos/stable/) is
12available offline, and is accessible during the
13installation. Very handy.
14
15### Setup
16
17The entire system is configured via
18`/etc/nixos/configuration.nix`. Wifi, `libinput` gestures,
19audio, locale settings, there are options for literally
20everything. You can declaratively write down the packages
21you want installed too. With fresh installs of most distros,
22I usually fumble with getting things like screen backlight
23and media keys to work. If I do manage to fix it, I can't
24carry it forward to future installations trivially. Getting
25all my hardware to work on NixOS is as easy as:
26
27```
28{
29 server.xserver.libinput.enable = true; # touchpad
30 programs.light.enable = true; # backlight
31 hardware.pulseaudio.enable = true; # audio
32 networking.wireless.enable = true; # wifi
33}
34```
35
36### Developing with Nix
37
38Nix makes it easy to enter environments that aren't affected
39by your system configuration using `nix-shell`.
40
41Builds may be generated by specifying a `default.nix` file,
42and running `nix-build`. Conventional package managers
43require you to specify a dependency list, but there is no
44guarantee that this list is complete. The package will build
45on your machine even if you forget a dependency. However,
46with Nix, packages are installed to `/nix/store`, and not
47global paths such as `/usr/bin/...`, if your project builds,
48it means you have included every last one.
49
50Issues on most my projects have been "unable to build
51because `libxcb` is missing", or "this version of `openssl`
52is too old". Tools like `cargo` and `pip` are poor package
53managers. While they *can* guarantee that Rust or Python
54dependencies are met, they make assumptions about the
55target system.
56
57For example, [this
58website](https://github.com/nerdypepper/site) is now built
59using Nix, anyone using Nix may simply, clone the repository
60and run `./generate.sh`, and it would *just work*, while
61keeping your global namespace clean™:
62
63```bash
64#! /usr/bin/env nix-shell
65#! nix-shell -i bash -p eva pandoc esh
66
67# some bash magic ;)
68```
69
70Dependencies are included with the `-p` flag, the shell
71script is executed with an interpreter, specified with the
72`-i` flag.
73
74### Impressions
75
76NixOS is by no means, simple. As a newcomer, using Nix was
77not easy, heck, I had to learn a purely functional, lazy
78language to just build programs. There is a lot to be
79desired on the tooling front as well. A well fleshed out LSP
80plugin would be nice ([rnix-lsp looks
81promising](https://github.com/nix-community/rnix-lsp)).
82
83Being able to rollback changes at a system level is cool.
84Package broke something? Just `nixos-rebuild switch
85--rollback`! Deleted `nix` by mistake? Find the binary in
86`/nix/store` and rollback! You aren't punished for not
87thinking twice.
88
89I don't see myself switching to anything else in the near
90future, NixOS does a lot of things right. If I ever need to
91reinstall NixOS, I can generate an [image of my current
92system](https://github.com/nix-community/nixos-generators).
93
94[![](https://u.peppe.rs/6m.png)](https://u.peppe.rs/6m.png)