path: root/docs/index.xml

<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
    <channel>
      <title>nerdypepper's μblog</title>
      <link>https://peppe.rs</link>
      <description>programming, design, software</description>
      <atom:link href="https://peppe.rs/index.xml" rel="self" type="application/rss+xml" />
      <image>
        <title>nerdypepper's μblog</title>
        <url>https://u.peppe.rs/n.png</url>
        <link>https://peppe.rs</link>
      </image>
      <language>en-us</language>
      <copyright>Creative Commons BY-NC-SA 4.0</copyright>
      <item>
<title>Curing A Case Of Git-UX</title>
<description>&lt;p&gt;Git worktrees are great, but they fall behind the venerable
&lt;code&gt;git checkout&lt;/code&gt; sometimes. I attempted to fix that with &lt;a
href="https://github.com/junegunn/fzf"&gt;fzf&lt;/a&gt; and a bit of bash.&lt;/p&gt;
&lt;p&gt;&lt;a href="https://asciinema.org/a/D297ztKRzpE4gAHbPTPmkqYps"&gt;&lt;img
src="https://asciinema.org/a/D297ztKRzpE4gAHbPTPmkqYps.svg" /&gt;&lt;/a&gt;&lt;/p&gt;
&lt;p&gt;Fear not if you haven’t heard of “worktrees”, I have included a
primer here.&lt;br /&gt;
&lt;a href="#what-makes-them-clunky"&gt;Skip the primer -&amp;gt;&lt;/a&gt;.&lt;/p&gt;
&lt;h3 id="why-worktrees"&gt;Why Worktrees?&lt;/h3&gt;
&lt;p&gt;Picture this. You are whacking away on a feature branch. Halfway
there, in fact. Your friend asks you fix something urgently. You proceed
to do one of three things:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;create a temporary branch, make a WIP commit, begin working on the
fix&lt;/li&gt;
&lt;li&gt;stash away your changes, begin working on the fix&lt;/li&gt;
&lt;li&gt;unfriend said friend for disturbing your flow&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;All of these options are … subpar. With the temporary branch, you are
forced to create a partial, non-working commit, and then reset said
commit once done with the fix. With the stash approach, you are required
to now keep a mental model of the stash, be aware of untracked files
that don’t get stashed by default, etc. Why won’t git just let you work
on two things at the same time without &lt;em&gt;thinking&lt;/em&gt; so much?&lt;/p&gt;
&lt;p&gt;That is exactly what worktrees let you do. Worktrees let you have
more than one checkout at a time, each checkout in a separate directory.
Like creating a new clone, but safer (it disallows checking out the same
branch twice) and a lot more space efficient (the new working tree is
“linked” to the “main” worktree, and a good amount of stuff is shared).
When your friend asks you to make the fix, you proceed like so:&lt;/p&gt;
&lt;ol type="1"&gt;
&lt;li&gt;Create a new working tree with:&lt;/li&gt;
&lt;/ol&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# git worktree add -b &amp;lt;branch-name&amp;gt; &amp;lt;path&amp;gt; &amp;lt;from&amp;gt;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-2"&gt;&lt;a href="#cb1-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="fu"&gt;git&lt;/span&gt; worktree add &lt;span class="at"&gt;-b&lt;/span&gt; fix-stuff /path/to/tree master&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;ol start="2" type="1"&gt;
&lt;li&gt;&lt;code&gt;cd&lt;/code&gt; into &lt;code&gt;/path/to/tree&lt;/code&gt;&lt;/li&gt;
&lt;li&gt;Fix, test, commit, push, party&lt;/li&gt;
&lt;li&gt;Go back to your work, &lt;code&gt;cd -&lt;/code&gt;&lt;/li&gt;
&lt;/ol&gt;
&lt;p&gt;Easy as cake. You didn’t have to settle for a partially working
commit, you didn’t to deal with this “stash” thing, &lt;em&gt;and&lt;/em&gt; you
didn’t have to unfriend your friend. Treating each branch as a directory
just &lt;em&gt;feels&lt;/em&gt; more intuitive, more UNIX-y.&lt;/p&gt;
&lt;p&gt;A few weeks later, you find yourself singing in praise of worktrees,
working on several things simultaneously. And at the same time, cursing
them for being a little … clunky.&lt;/p&gt;
&lt;h3 id="what-makes-them-clunky"&gt;What makes them clunky?&lt;/h3&gt;
&lt;p&gt;Worktrees are great at what they claim to do. They stay out of the
way when you need a checkout posthaste. However, as you start using them
regularly, you realize they are not as flexible as
&lt;code&gt;git checkout&lt;/code&gt; or &lt;code&gt;git switch&lt;/code&gt;.&lt;/p&gt;
&lt;h4 id="branch-hopping"&gt;Branch-hopping&lt;/h4&gt;
&lt;p&gt;You can &lt;code&gt;git checkout &amp;lt;branch&amp;gt;&lt;/code&gt; from anywhere within
a git repository. You can’t “jump” to a worktree in the same fashion.
The closest you can get, is to run &lt;code&gt;git worktree list&lt;/code&gt;, copy
the path corresponding to your branch, and &lt;code&gt;cd&lt;/code&gt; into it.&lt;/p&gt;
&lt;p&gt;Branch-hopping with the good ol’ git-checkout:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# anywhere, anytime&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;λ&lt;/span&gt; git checkout feature/is-ascii-octdigit&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Meanwhile, in worktree world:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# keeping these paths in your head is hard&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-2"&gt;&lt;a href="#cb3-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;λ&lt;/span&gt; git worktree list&lt;/span&gt;
&lt;span id="cb3-3"&gt;&lt;a href="#cb3-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;~/worktrees/rustc/master&lt;/span&gt;                 eac6c33bc63 &lt;span class="pp"&gt;[&lt;/span&gt;&lt;span class="ss"&gt;master&lt;/span&gt;&lt;span class="pp"&gt;]&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-4"&gt;&lt;a href="#cb3-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;~/worktrees/rustc/improve-std-char-docs&lt;/span&gt;  94cba88553e &lt;span class="pp"&gt;[&lt;/span&gt;&lt;span class="ss"&gt;improve&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;std&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;char&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;docs&lt;/span&gt;&lt;span class="pp"&gt;]&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-5"&gt;&lt;a href="#cb3-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;~/worktrees/rustc/is-ascii-octdigit&lt;/span&gt;      bc57be3af7a &lt;span class="pp"&gt;[&lt;/span&gt;&lt;span class="ss"&gt;feature/is&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;ascii&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;octdigit&lt;/span&gt;&lt;span class="pp"&gt;]&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-6"&gt;&lt;a href="#cb3-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;~/my/other/path/oh/god&lt;/span&gt;                   op57or3ns7n &lt;span class="pp"&gt;[&lt;/span&gt;&lt;span class="ss"&gt;fix/some&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;error&lt;/span&gt;&lt;span class="pp"&gt;]&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-7"&gt;&lt;a href="#cb3-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb3-8"&gt;&lt;a href="#cb3-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;λ&lt;/span&gt; cd ~/worktrees/rustc/is-ascii-octdigit&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h4 id="branch-previewing"&gt;Branch-previewing&lt;/h4&gt;
&lt;p&gt;You can “preview” branches with &lt;code&gt;git branch -v&lt;/code&gt;. However,
to get an idea of what “recent activity” on a worktree looks like, you
might need some juggling. You can’t glean much info about a worktree in
a jiffy.&lt;/p&gt;
&lt;p&gt;Branch-previewing with the good ol’ git-branch:&lt;/p&gt;
&lt;div class="sourceCode" id="cb4"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb4-1"&gt;&lt;a href="#cb4-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;λ&lt;/span&gt; git branch &lt;span class="at"&gt;-v&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb4-2"&gt;&lt;a href="#cb4-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;+&lt;/span&gt; feature/is-ascii-octdigit bc57be3af7a introduce {char, u8}::is_ ...&lt;/span&gt;
&lt;span id="cb4-3"&gt;&lt;a href="#cb4-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;+&lt;/span&gt; improve-std-char-docs     94cba88553e add whitespace in assert ...&lt;/span&gt;
&lt;span id="cb4-4"&gt;&lt;a href="#cb4-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;*&lt;/span&gt; master                    eac6c33bc63 Auto merge of &lt;span class="co"&gt;#100869 - n ...&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Meanwhile in worktree wonderland:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;λ git worktree list
~/worktrees/rustc/master                 eac6c33bc63 [master]
~/worktrees/rustc/improve-std-char-docs  94cba88553e [improve-std-char-docs]
~/worktrees/rustc/is-ascii-octdigit      bc57be3af7a [feature/is-ascii-octdigit]

# aha, so ../is-ascii-octdigit corresponds to `feature/is-ascii-octdigit`
λ git log feature/is-ascii-octdigit
bc57be3af7a introduce {char, u8}::is_ascii_octdigit
eac6c33bc63 Auto merge of #100869 - nnethercote:repl ...
b32223fec10 Auto merge of #100707 - dzvon:fix-typo,  ...
aa857eb953e Auto merge of #100537 - petrochenkov:pic ...

# extra work to make the branch &amp;lt;-&amp;gt; worktree correspondence&lt;/code&gt;&lt;/pre&gt;
&lt;h4 id="shell-completions"&gt;Shell completions&lt;/h4&gt;
&lt;p&gt;Lastly, you can bank on shell completions to fill in your branch
whilst using &lt;code&gt;git checkout&lt;/code&gt;. Worktrees have no such
conveniences.&lt;/p&gt;
&lt;p&gt;We can mend these minor faults with fzf.&lt;/p&gt;
&lt;h3 id="unclunkifying-worktrees"&gt;Unclunkifying worktrees&lt;/h3&gt;
&lt;p&gt;I’d suggest looking up &lt;a
href="https://github.com/junegunn/fzf"&gt;fzf&lt;/a&gt; (or &lt;a
href="https://github.com/lotabout/skim"&gt;skim&lt;/a&gt; or &lt;a
href="https://github.com/jhawthorn/fzy"&gt;fzy&lt;/a&gt;). These things make it
cake-easy to add interactivity to your shell. Onto fixing the first
minor fault, the inability to “jump” to a worktree from anywhere within
a git repository.&lt;/p&gt;
&lt;p&gt;I have a little function called &lt;code&gt;gwj&lt;/code&gt; which stands for
“git worktree jump”. The idea is to list all the worktrees, select one
with fzf, and &lt;code&gt;cd&lt;/code&gt; to it upon selection:&lt;/p&gt;
&lt;div class="sourceCode" id="cb6"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb6-1"&gt;&lt;a href="#cb6-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="fu"&gt;gwj ()&lt;/span&gt; &lt;span class="kw"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb6-2"&gt;&lt;a href="#cb6-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="bu"&gt;local&lt;/span&gt; &lt;span class="va"&gt;out&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb6-3"&gt;&lt;a href="#cb6-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="va"&gt;out&lt;/span&gt;&lt;span class="op"&gt;=&lt;/span&gt;&lt;span class="va"&gt;$(&lt;/span&gt;&lt;span class="fu"&gt;git&lt;/span&gt; worktree list &lt;span class="kw"&gt;|&lt;/span&gt; &lt;span class="ex"&gt;fzf&lt;/span&gt; &lt;span class="kw"&gt;|&lt;/span&gt; &lt;span class="fu"&gt;awk&lt;/span&gt; &lt;span class="st"&gt;&amp;#39;{print $1}&amp;#39;&lt;/span&gt;&lt;span class="va"&gt;)&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb6-4"&gt;&lt;a href="#cb6-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="bu"&gt;cd&lt;/span&gt; &lt;span class="va"&gt;$out&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb6-5"&gt;&lt;a href="#cb6-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;That is all of it really. Head into a git repository:&lt;/p&gt;
&lt;div class="sourceCode" id="cb7"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb7-1"&gt;&lt;a href="#cb7-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# here, &amp;quot;master&amp;quot; is a directory, which contains my main&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-2"&gt;&lt;a href="#cb7-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# worktree: a checkout of the master branch on rust-lang/rust &lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-3"&gt;&lt;a href="#cb7-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;λ&lt;/span&gt; cd ~/worktrees/rustc/master/library/core/src&lt;/span&gt;
&lt;span id="cb7-4"&gt;&lt;a href="#cb7-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;λ&lt;/span&gt; &lt;span class="co"&gt;# hack away&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Preferably one with a few worktrees:&lt;/p&gt;
&lt;div class="sourceCode" id="cb8"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb8-1"&gt;&lt;a href="#cb8-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;λ&lt;/span&gt; git worktree list&lt;/span&gt;
&lt;span id="cb8-2"&gt;&lt;a href="#cb8-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;~/worktrees/rustc/master&lt;/span&gt;                 eac6c33bc63 &lt;span class="pp"&gt;[&lt;/span&gt;&lt;span class="ss"&gt;master&lt;/span&gt;&lt;span class="pp"&gt;]&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb8-3"&gt;&lt;a href="#cb8-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;~/worktrees/rustc/improve-std-char-docs&lt;/span&gt;  94cba88553e &lt;span class="pp"&gt;[&lt;/span&gt;&lt;span class="ss"&gt;improve&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;std&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;char&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;docs&lt;/span&gt;&lt;span class="pp"&gt;]&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb8-4"&gt;&lt;a href="#cb8-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;~/worktrees/rustc/is-ascii-octdigit&lt;/span&gt;      bc57be3af7a &lt;span class="pp"&gt;[&lt;/span&gt;&lt;span class="ss"&gt;feature/is&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;ascii&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;octdigit&lt;/span&gt;&lt;span class="pp"&gt;]&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;And hit &lt;code&gt;gwj&lt;/code&gt; (pretend that the pipe, |, is your
cursor):&lt;/p&gt;
&lt;div class="sourceCode" id="cb9"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb9-1"&gt;&lt;a href="#cb9-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;λ&lt;/span&gt; gwj&lt;/span&gt;
&lt;span id="cb9-2"&gt;&lt;a href="#cb9-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;&amp;gt;&lt;/span&gt; &lt;span class="kw"&gt;|&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb9-3"&gt;&lt;a href="#cb9-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="ex"&gt;4/4&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb9-4"&gt;&lt;a href="#cb9-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;&amp;gt;&lt;/span&gt; ~/worktrees/rustc/master                 &lt;span class="ex"&gt;eac6c33bc63&lt;/span&gt; &lt;span class="pp"&gt;[&lt;/span&gt;&lt;span class="ss"&gt;master&lt;/span&gt;&lt;span class="pp"&gt;]&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb9-5"&gt;&lt;a href="#cb9-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="ex"&gt;~/worktrees/rustc/improve-std-char-docs&lt;/span&gt;  94cba88553e &lt;span class="pp"&gt;[&lt;/span&gt;&lt;span class="ss"&gt;improve&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;std&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;char&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;docs&lt;/span&gt;&lt;span class="pp"&gt;]&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb9-6"&gt;&lt;a href="#cb9-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="ex"&gt;~/worktrees/rustc/is-ascii-octdigit&lt;/span&gt;      bc57be3af7a &lt;span class="pp"&gt;[&lt;/span&gt;&lt;span class="ss"&gt;feature/is&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;ascii&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;octdigit&lt;/span&gt;&lt;span class="pp"&gt;]&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Approximately type in your branch of choice:&lt;/p&gt;
&lt;div class="sourceCode" id="cb10"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb10-1"&gt;&lt;a href="#cb10-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;λ&lt;/span&gt; gwj&lt;/span&gt;
&lt;span id="cb10-2"&gt;&lt;a href="#cb10-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;&amp;gt;&lt;/span&gt; docs&lt;span class="kw"&gt;|&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb10-3"&gt;&lt;a href="#cb10-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="ex"&gt;4/4&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb10-4"&gt;&lt;a href="#cb10-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;&amp;gt;&lt;/span&gt; ~/worktrees/rustc/improve-std-char-docs  &lt;span class="ex"&gt;94cba88553e&lt;/span&gt; &lt;span class="pp"&gt;[&lt;/span&gt;&lt;span class="ss"&gt;improve&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;std&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;char&lt;/span&gt;&lt;span class="pp"&gt;-&lt;/span&gt;&lt;span class="ss"&gt;docs&lt;/span&gt;&lt;span class="pp"&gt;]&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;And hit enter. You should find yourself in the selected worktree.&lt;/p&gt;
&lt;p&gt;Onward, to the next fault, lack of preview-bility. We can utilize
fzf’s aptly named &lt;code&gt;--preview&lt;/code&gt; flag, to, well, preview our
worktree before performing a selection:&lt;/p&gt;
&lt;div class="sourceCode" id="cb11"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb11-1"&gt;&lt;a href="#cb11-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="fu"&gt;gwj ()&lt;/span&gt; &lt;span class="kw"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-2"&gt;&lt;a href="#cb11-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="bu"&gt;local&lt;/span&gt; &lt;span class="va"&gt;out&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-3"&gt;&lt;a href="#cb11-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="va"&gt;out&lt;/span&gt;&lt;span class="op"&gt;=&lt;/span&gt;&lt;span class="va"&gt;$(&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-4"&gt;&lt;a href="#cb11-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="fu"&gt;git&lt;/span&gt; worktree list &lt;span class="kw"&gt;|&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-5"&gt;&lt;a href="#cb11-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="ex"&gt;fzf&lt;/span&gt; &lt;span class="at"&gt;--preview&lt;/span&gt;&lt;span class="op"&gt;=&lt;/span&gt;&lt;span class="st"&gt;&amp;#39;git log --oneline -n10 {2}&amp;#39;&lt;/span&gt; &lt;span class="kw"&gt;|&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-6"&gt;&lt;a href="#cb11-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="fu"&gt;awk&lt;/span&gt; &lt;span class="st"&gt;&amp;#39;{print $1}&amp;#39;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-7"&gt;&lt;a href="#cb11-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="va"&gt;)&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-8"&gt;&lt;a href="#cb11-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="bu"&gt;cd&lt;/span&gt; &lt;span class="va"&gt;$out&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-9"&gt;&lt;a href="#cb11-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Once again, hit &lt;code&gt;gwj&lt;/code&gt; inside a git repository with linked
worktrees:&lt;/p&gt;
&lt;div class="sourceCode" id="cb12"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb12-1"&gt;&lt;a href="#cb12-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;λ&lt;/span&gt; gwj&lt;/span&gt;
&lt;span id="cb12-2"&gt;&lt;a href="#cb12-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;╭─────────────────────────────────────────────────────────╮&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-3"&gt;&lt;a href="#cb12-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│&lt;/span&gt; eac6c33bc63 Auto merge of 100869 nnethercote:replace... │&lt;/span&gt;
&lt;span id="cb12-4"&gt;&lt;a href="#cb12-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│&lt;/span&gt; b32223fec10 Auto merge of 100707 dzvon:fix-typo, r=d... │&lt;/span&gt;
&lt;span id="cb12-5"&gt;&lt;a href="#cb12-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│&lt;/span&gt; aa857eb953e Auto merge of 100537 petrochenkov:picche... │&lt;/span&gt;
&lt;span id="cb12-6"&gt;&lt;a href="#cb12-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│&lt;/span&gt; 3892b7074da Auto merge of 100210 mystor:proc_macro_d... │&lt;/span&gt;
&lt;span id="cb12-7"&gt;&lt;a href="#cb12-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│&lt;/span&gt; db00199d999 Auto merge of 101249 matthiaskrgr:rollup... │&lt;/span&gt;
&lt;span id="cb12-8"&gt;&lt;a href="#cb12-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│&lt;/span&gt; 14d216d33ba Rollup merge of 101240 JohnTitor:JohnTit... │&lt;/span&gt;
&lt;span id="cb12-9"&gt;&lt;a href="#cb12-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│&lt;/span&gt; 3da66f03531 Rollup merge of 101236 thomcc:winfs-noze... │&lt;/span&gt;
&lt;span id="cb12-10"&gt;&lt;a href="#cb12-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│&lt;/span&gt; 0620f6e90af Rollup merge of 101230 davidtwco:transla... │&lt;/span&gt;
&lt;span id="cb12-11"&gt;&lt;a href="#cb12-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│&lt;/span&gt; c30c42ee299 Rollup merge of 101229 mgeisler:link-try... │&lt;/span&gt;
&lt;span id="cb12-12"&gt;&lt;a href="#cb12-12" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│&lt;/span&gt; e5356712b9e Rollup merge of 101165 ldm0:drain_to_ite... │&lt;/span&gt;
&lt;span id="cb12-13"&gt;&lt;a href="#cb12-13" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;╰─────────────────────────────────────────────────────────╯&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-14"&gt;&lt;a href="#cb12-14" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;&amp;gt;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-15"&gt;&lt;a href="#cb12-15" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="ex"&gt;4/4&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-16"&gt;&lt;a href="#cb12-16" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;&amp;gt;&lt;/span&gt; /home/np/worktrees/compiler/master                 &lt;span class="ex"&gt;eac6c...&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-17"&gt;&lt;a href="#cb12-17" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="ex"&gt;/home/np/worktrees/compiler/improve-std-char-docs&lt;/span&gt;  94cba...&lt;/span&gt;
&lt;span id="cb12-18"&gt;&lt;a href="#cb12-18" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="ex"&gt;/home/np/worktrees/compiler/is-ascii-octdigit&lt;/span&gt;      bc57b...&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;A fancy preview of the last 10 commits on the branch that the
selected worktree corresponds to. In other words, sight for sore eyes.
Our little script is already shaping up to be useful, you hit
&lt;code&gt;gwj&lt;/code&gt;, browse through your worktrees, preview each one and
automatically &lt;code&gt;cd&lt;/code&gt; to your selection. But we are not done
yet.&lt;/p&gt;
&lt;p&gt;The last fault was lack shell completions. A quick review of what a
shell completion really does:&lt;/p&gt;
&lt;div class="sourceCode" id="cb13"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb13-1"&gt;&lt;a href="#cb13-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;λ&lt;/span&gt; git checkout f&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;tab&lt;span class="op"&gt;&amp;gt;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb13-2"&gt;&lt;a href="#cb13-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;feature/is-ascii-octdigit&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb13-3"&gt;&lt;a href="#cb13-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;fix/some-error&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb13-4"&gt;&lt;a href="#cb13-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;format-doc-tests&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb13-5"&gt;&lt;a href="#cb13-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb13-6"&gt;&lt;a href="#cb13-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;λ&lt;/span&gt; git checkout feat&lt;span class="op"&gt;&amp;lt;&lt;/span&gt;tab&lt;span class="op"&gt;&amp;gt;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb13-7"&gt;&lt;a href="#cb13-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb13-8"&gt;&lt;a href="#cb13-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;λ&lt;/span&gt; git checkout feature/is-ascii-octdigit&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Each time you hit “tab”, the shell produces a few “completion
candidates”, and once you have just a single candidate left, the shell
inserts that for you directly into your edit line. Of course, this
process varies from shell to shell.&lt;/p&gt;
&lt;p&gt;fzf narrows down your options as you type into the prompt, but you
still have to:&lt;/p&gt;
&lt;ol type="1"&gt;
&lt;li&gt;Type &lt;code&gt;gwj&lt;/code&gt;&lt;/li&gt;
&lt;li&gt;Hit enter&lt;/li&gt;
&lt;li&gt;Type out a query and narrow down your search&lt;/li&gt;
&lt;li&gt;Hit enter&lt;/li&gt;
&lt;/ol&gt;
&lt;p&gt;We can speed that up a bit, have fzf narrow down the candidates on
startup, just like our shell does:&lt;/p&gt;
&lt;div class="sourceCode" id="cb14"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb14-1"&gt;&lt;a href="#cb14-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="fu"&gt;gwj ()&lt;/span&gt; &lt;span class="kw"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb14-2"&gt;&lt;a href="#cb14-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="bu"&gt;local&lt;/span&gt; &lt;span class="va"&gt;out&lt;/span&gt; &lt;span class="va"&gt;query&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb14-3"&gt;&lt;a href="#cb14-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="va"&gt;query&lt;/span&gt;&lt;span class="op"&gt;=&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;${1&lt;/span&gt;&lt;span class="op"&gt;:-&lt;/span&gt; &lt;span class="va"&gt;}&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb14-4"&gt;&lt;a href="#cb14-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="va"&gt;out&lt;/span&gt;&lt;span class="op"&gt;=&lt;/span&gt;&lt;span class="va"&gt;$(&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb14-5"&gt;&lt;a href="#cb14-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="fu"&gt;git&lt;/span&gt; worktree list &lt;span class="kw"&gt;|&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb14-6"&gt;&lt;a href="#cb14-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="ex"&gt;fzf&lt;/span&gt; &lt;span class="at"&gt;--preview&lt;/span&gt;&lt;span class="op"&gt;=&lt;/span&gt;&lt;span class="st"&gt;&amp;#39;git log --oneline -n10 {2}&amp;#39;&lt;/span&gt; &lt;span class="at"&gt;--query&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;$query&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt; &lt;span class="at"&gt;-1&lt;/span&gt; &lt;span class="kw"&gt;|&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb14-7"&gt;&lt;a href="#cb14-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="fu"&gt;awk&lt;/span&gt; &lt;span class="st"&gt;&amp;#39;{print $1}&amp;#39;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb14-8"&gt;&lt;a href="#cb14-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="va"&gt;)&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb14-9"&gt;&lt;a href="#cb14-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="bu"&gt;cd&lt;/span&gt; &lt;span class="va"&gt;$out&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb14-10"&gt;&lt;a href="#cb14-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The change is extremely tiny, blink-and-you’ll-miss-it kinda tiny. We
added a little &lt;code&gt;--query&lt;/code&gt; flag, that allows you to prefill the
prompt, and the &lt;code&gt;-1&lt;/code&gt; flag, that avoids the interactive finder
if only one match exists on startup:&lt;/p&gt;
&lt;div class="sourceCode" id="cb15"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb15-1"&gt;&lt;a href="#cb15-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# skip through the fzf prompt:&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb15-2"&gt;&lt;a href="#cb15-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;λ&lt;/span&gt; gwj master&lt;/span&gt;
&lt;span id="cb15-3"&gt;&lt;a href="#cb15-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# cd -- ~/worktrees/rustc/master&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb15-4"&gt;&lt;a href="#cb15-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb15-5"&gt;&lt;a href="#cb15-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# more than one option, we end up in the interactive finder&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb15-6"&gt;&lt;a href="#cb15-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;λ&lt;/span&gt; gwj improve&lt;/span&gt;
&lt;span id="cb15-7"&gt;&lt;a href="#cb15-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;╭─────────────────────────────────────────────────────────╮&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb15-8"&gt;&lt;a href="#cb15-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│&lt;/span&gt; eac6c33bc63 Auto merge of 100869 nnethercote:replace... │&lt;/span&gt;
&lt;span id="cb15-9"&gt;&lt;a href="#cb15-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│&lt;/span&gt; b32223fec10 Auto merge of 100707 dzvon:fix-typo, r=d... │&lt;/span&gt;
&lt;span id="cb15-10"&gt;&lt;a href="#cb15-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│&lt;/span&gt; aa857eb953e Auto merge of 100537 petrochenkov:picche... │&lt;/span&gt;
&lt;span id="cb15-11"&gt;&lt;a href="#cb15-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;╰─────────────────────────────────────────────────────────╯&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb15-12"&gt;&lt;a href="#cb15-12" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;&amp;gt;&lt;/span&gt; improve&lt;/span&gt;
&lt;span id="cb15-13"&gt;&lt;a href="#cb15-13" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="ex"&gt;2/2&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb15-14"&gt;&lt;a href="#cb15-14" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;&amp;gt;&lt;/span&gt; /home/np/worktrees/compiler/improve-const-perf     &lt;span class="ex"&gt;eac6c...&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb15-15"&gt;&lt;a href="#cb15-15" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="ex"&gt;/home/np/worktrees/compiler/improve-std-char-docs&lt;/span&gt;  94cba...&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Throw some error handling in there, hook up a similar script to
improve the UX of &lt;code&gt;git worktree remove&lt;/code&gt;, go wild. A few more
helpers I’ve got:&lt;/p&gt;
&lt;div class="sourceCode" id="cb16"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb16-1"&gt;&lt;a href="#cb16-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# gwa /path/to/branch-name&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb16-2"&gt;&lt;a href="#cb16-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# creates a new branch and &amp;quot;switches&amp;quot; to it&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb16-3"&gt;&lt;a href="#cb16-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;function&lt;/span&gt;&lt;span class="fu"&gt; gwa ()&lt;/span&gt; &lt;span class="kw"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb16-4"&gt;&lt;a href="#cb16-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="fu"&gt;git&lt;/span&gt; worktree add &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; &lt;span class="kw"&gt;&amp;amp;&amp;amp;&lt;/span&gt; &lt;span class="bu"&gt;cd&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="st"&gt;&amp;quot;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb16-5"&gt;&lt;a href="#cb16-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb16-6"&gt;&lt;a href="#cb16-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb16-7"&gt;&lt;a href="#cb16-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="bu"&gt;alias&lt;/span&gt; gwls=&lt;span class="st"&gt;&amp;quot;git worktree list&amp;quot;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;</description>
<link>https://peppe.rs/posts/curing_a_case_of_git-UX/</link>
<pubDate>Sat, 03 Sep 2022 03:18:00 +0000</pubDate>
<guid>https://peppe.rs/posts/curing_a_case_of_git-UX/</guid>
</item>
<item>
<title>Programming On 34 Keys</title>
<description>&lt;p&gt;Minimizing your keyboard layout is a slippery slope. A few months
ago, I built the &lt;a
href="https://github.com/icyphox/ferricy"&gt;Ferricy&lt;/a&gt;, a
34-key-split-ortho-ergo keyboard. The Ferricy is a fork of the &lt;a
href="https://github.com/davidphilipbarr/Sweep/tree/main/Sweep%20Bling%20MX"&gt;Ferris
Sweep MX Bling&lt;/a&gt;.&lt;/p&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/otz.jpg"
alt="The Ferricy, designed by icyphox" /&gt;
&lt;figcaption aria-hidden="true"&gt;The Ferricy, designed by &lt;a
href="https://icyphox.sh"&gt;icyphox&lt;/a&gt;&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;p&gt;My daily use consists of a bit of prose and a lot of program, my
layout has evolved accordingly.&lt;/p&gt;
&lt;h1 id="base-layer"&gt;Base Layer&lt;/h1&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/base.png" alt="Colemak with no mods" /&gt;
&lt;figcaption aria-hidden="true"&gt;Colemak with no mods&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;p&gt;The base layer contains alphabets, four symbols and four whitespace
keys:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;Alphas: Stock Colemak, with no modifications whatsoever&lt;/li&gt;
&lt;li&gt;Symbols: &lt;code&gt;. , / ;&lt;/code&gt;&lt;/li&gt;
&lt;li&gt;Whitespace: tab, space, enter, backspace (from left to right)&lt;/li&gt;
&lt;/ul&gt;
&lt;h1 id="layers"&gt;Layers&lt;/h1&gt;
&lt;p&gt;Keyboard input is complex and it is impossible to skirt around it.
You can either use a keyboard with enough keys to supply all possible
inputs (a mechanical burden), or you can use firmware to supply all
possible inputs (a cognitive burden). Layers are a cognitive burden.&lt;/p&gt;
&lt;p&gt;I use 3 layers, heavily inspired by &lt;a
href="https://github.com/manna-harbour/miryoku"&gt;Miryoku&lt;/a&gt;, but tuned
for programming. Excluding the base Colemak layer:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;&lt;code&gt;NAV&lt;/code&gt;: activated on holding &lt;code&gt;space&lt;/code&gt; (left
thumb)&lt;/li&gt;
&lt;li&gt;&lt;code&gt;NUM&lt;/code&gt;: activated on holding &lt;code&gt;tab&lt;/code&gt; (left
thumb)&lt;/li&gt;
&lt;li&gt;&lt;code&gt;SYM&lt;/code&gt;: activated on holding &lt;code&gt;enter&lt;/code&gt; (right
thumb)&lt;/li&gt;
&lt;/ul&gt;
&lt;h2 id="the-nav-layer"&gt;The &lt;code&gt;NAV&lt;/code&gt; Layer&lt;/h2&gt;
&lt;p&gt;As the name suggests, this layer is focused on navigation. Arrow keys
and the likes.&lt;/p&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/nav.png" alt="NAV, on holding space" /&gt;
&lt;figcaption aria-hidden="true"&gt;&lt;code&gt;NAV&lt;/code&gt;, on holding
&lt;code&gt;space&lt;/code&gt;&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;p&gt;Using Vim and Colemak means you lose out on HJKL navigation. However,
on activating the &lt;code&gt;NAV&lt;/code&gt; layer, the right home-row is
converted into arrow keys. In essence, by holding space, I can navigate
Vim with the home-row, or Firefox, or my PDF reader. I no longer need to
look for software that allows Vim navigation keys, because it is baked
into the firmware!&lt;/p&gt;
&lt;p&gt;My Vim motions are not limited to HJKL. In fact, my Vim motions are
rarely HJKL. I tend to use &lt;code&gt;}&lt;/code&gt; (next paragraph) and
&lt;code&gt;)&lt;/code&gt; (next sentence) more often. As a result, these have found
their way into my &lt;code&gt;NAV&lt;/code&gt; layer, over the likes of
&lt;code&gt;PgDown&lt;/code&gt; and &lt;code&gt;End&lt;/code&gt;. Having brackets at my index
and middle fingers is nice for programming too.&lt;/p&gt;
&lt;h2 id="the-sym-layer"&gt;The &lt;code&gt;SYM&lt;/code&gt; Layer&lt;/h2&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/sym.png" alt="SYM, on holding enter" /&gt;
&lt;figcaption aria-hidden="true"&gt;&lt;code&gt;SYM&lt;/code&gt;, on holding
&lt;code&gt;enter&lt;/code&gt;&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;p&gt;This layer contains all the symbols that you would find by hitting
&lt;code&gt;Shift&lt;/code&gt; and a key on the number row. Probably noteworthy to
Vim users: the symbols are arranged in the form of a mirrored numpad for
exactly one reason: to move &lt;code&gt;$&lt;/code&gt; to the left of
&lt;code&gt;^&lt;/code&gt;. It has always annoyed me that &lt;code&gt;$&lt;/code&gt; moves the
cursor to the end of the line and &lt;code&gt;^&lt;/code&gt; moves it to the
beginning, but their position on a typical number row are reversed, 4
comes before 6.&lt;/p&gt;
&lt;h2 id="the-num-layer"&gt;The &lt;code&gt;NUM&lt;/code&gt; layer&lt;/h2&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/num.png" alt="NUM, on holding tab" /&gt;
&lt;figcaption aria-hidden="true"&gt;&lt;code&gt;NUM&lt;/code&gt;, on holding
&lt;code&gt;tab&lt;/code&gt;&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;p&gt;Another deviation from Miryoku, the numpad just feels &lt;em&gt;right&lt;/em&gt;
on my &lt;em&gt;right&lt;/em&gt; hand.&lt;/p&gt;
&lt;h1 id="zmk-combos"&gt;ZMK Combos&lt;/h1&gt;
&lt;p&gt;If you have been paying close attention, you might have noticed that
&lt;code&gt;escape&lt;/code&gt; didn’t make it to any layer. &lt;code&gt;escape&lt;/code&gt; is
too crucial to put on a non-base layer, but at the same time, not as
important to deserve a place on the base layer. That is where ZMK’s
combos come in. Combos let you tap any number of keys, and combine them
to form a single key. I have combos set up for underscore, minus, escape
and caps-word (more on caps-word later):&lt;/p&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/combos.png"
alt="Combos are almost piano-like" /&gt;
&lt;figcaption aria-hidden="true"&gt;Combos are almost piano-like&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h1 id="home-row-mods"&gt;Home-row Mods&lt;/h1&gt;
&lt;p&gt;Inherited from Miryoku, I have home-row mods for activating
&lt;code&gt;Super&lt;/code&gt;, &lt;code&gt;Alt&lt;/code&gt;, &lt;code&gt;Shift&lt;/code&gt;,
&lt;code&gt;Ctrl&lt;/code&gt; and &lt;code&gt;Hyper&lt;/code&gt;
(&lt;code&gt;Ctrl + Shift + Alt + Super&lt;/code&gt;). The idea is to send
&lt;code&gt;T&lt;/code&gt; on tap and &lt;code&gt;Ctrl&lt;/code&gt; on hold. Home-row mods are
fairly popular, so I’ll not go into the details.&lt;/p&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/homerow.png"
alt="Super, Alt, Shift, Ctrl, Hyper; on the left half, and mirrored on the right half" /&gt;
&lt;figcaption aria-hidden="true"&gt;Super, Alt, Shift, Ctrl, Hyper; on the
left half, and mirrored on the right half&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;p&gt;&lt;code&gt;Hyper&lt;/code&gt; bridges the gap between firmware and software. You
can never configure key combination that, opens Firefox, for example,
through firmware alone. However, with the &lt;code&gt;Hyper&lt;/code&gt; key, and
some &lt;code&gt;sxhkd&lt;/code&gt; magic, you can emulate that. Pressing
&lt;code&gt;Hyper + F&lt;/code&gt; on a keyboard is just two keys, but the key codes
sent are &lt;code&gt;Ctrl + Shift + Alt + Super + F&lt;/code&gt;. That key
combination is not intercepted by any application as a shortcut, except
for the following &lt;code&gt;sxhkd&lt;/code&gt; stanza:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;super&lt;/span&gt; + alt + shift + ctrl + f&lt;/span&gt;
&lt;span id="cb1-2"&gt;&lt;a href="#cb1-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="ex"&gt;xdotool&lt;/span&gt; search &lt;span class="st"&gt;&amp;quot;Mozilla Firefox&amp;quot;&lt;/span&gt; windowactivate&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Alternatively, you can intercept unused &lt;code&gt;F&lt;/code&gt; keys:
&lt;code&gt;F13&lt;/code&gt; through &lt;code&gt;F24&lt;/code&gt;.&lt;/p&gt;
&lt;p&gt;Home-row mods are mirrored on each half because it would be
impossible to hit &lt;code&gt;Ctrl + T&lt;/code&gt; if not; they lie on the same
key.&lt;/p&gt;
&lt;h1 id="caps-word"&gt;Caps-word&lt;/h1&gt;
&lt;p&gt;Caps-word is a clever caps-lock, built into ZMK. Typing out constants
such as &lt;code&gt;PORT&lt;/code&gt; with home-row mods would look like this:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;hold &lt;code&gt;e&lt;/code&gt; (shift) on left hand, and tap &lt;code&gt;p&lt;/code&gt; on
right hand&lt;/li&gt;
&lt;li&gt;hold &lt;code&gt;e&lt;/code&gt; (shift) on left hand, and tap &lt;code&gt;o&lt;/code&gt; on
right hand&lt;/li&gt;
&lt;li&gt;hold &lt;code&gt;s&lt;/code&gt; (shift) on right hand, and tap &lt;code&gt;r&lt;/code&gt; on
left hand&lt;/li&gt;
&lt;li&gt;hold &lt;code&gt;s&lt;/code&gt; (shift) on right hand, and tap &lt;code&gt;t&lt;/code&gt; on
left hand&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;This hold-alternate-hold dance gets tiring quickly. With caps-word,
however:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;toggle &lt;code&gt;caps_word&lt;/code&gt;&lt;/li&gt;
&lt;li&gt;type out &lt;code&gt;p&lt;/code&gt;, &lt;code&gt;o&lt;/code&gt;, &lt;code&gt;r&lt;/code&gt;,
&lt;code&gt;t&lt;/code&gt;&lt;/li&gt;
&lt;li&gt;hit a &lt;em&gt;break&lt;/em&gt; character (space, enter will do)&lt;/li&gt;
&lt;li&gt;continue&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;Caps-word automatically disables capitalization upon encountering a
breaking character, (which are space, enter or any modifier, by default)
right in the firmware!&lt;/p&gt;
&lt;h1 id="findings"&gt;Findings&lt;/h1&gt;
&lt;p&gt;34-keys has been reasonably comfortable to use, for both prose and
program. My palms do not move across the desk at all, as I reach for
keys. I mostly write Rust and Bash, and my layout has evolved to
accomodate special characters from their grammars (angled brackets and
hyphens, specifically). If you are on a similar journey, I would suggest
focusing on accuracy and comfort over speed. Speed comes with time.&lt;/p&gt;</description>
<link>https://peppe.rs/posts/programming_on_34_keys/</link>
<pubDate>Sun, 28 Aug 2022 13:51:00 +0000</pubDate>
<guid>https://peppe.rs/posts/programming_on_34_keys/</guid>
</item>
<item>
<title>A Reference Counted Afterlife</title>
<description>&lt;p&gt;I took interest in the Egyptian rendition of the afterlife
recently.&lt;/p&gt;
&lt;h3 id="parts-of-the-soul"&gt;Parts of the Soul&lt;/h3&gt;
&lt;p&gt;Ancient Egyptians believed that the soul comprised of several
components:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;&lt;em&gt;ren&lt;/em&gt;&lt;/li&gt;
&lt;li&gt;&lt;em&gt;ka&lt;/em&gt;&lt;/li&gt;
&lt;li&gt;&lt;em&gt;ib&lt;/em&gt;&lt;/li&gt;
&lt;li&gt;&lt;em&gt;ba&lt;/em&gt;&lt;/li&gt;
&lt;li&gt;&lt;em&gt;sheut&lt;/em&gt;&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;Egyptians emphasized on preserving the different parts of the soul.
Mummification for example, served to preserve the physical part of the
soul. The other components have their respective preservation
strategies.&lt;/p&gt;
&lt;p&gt;Of all of these bits, I find &lt;em&gt;ren&lt;/em&gt;, which simply means
&lt;em&gt;name&lt;/em&gt;, to be the most interesting. &lt;em&gt;Ba&lt;/em&gt;, the human-headed
chicken that represents &lt;em&gt;personality&lt;/em&gt;, is a close favourite.&lt;/p&gt;
&lt;p&gt;&lt;em&gt;Ren&lt;/em&gt; is the name given to a person at birth. Egyptians
believed that this portion of the soul would continue to live on for as
long as it was spoken. If you were someone worthy of continued
existence, your name would be inscribed all over the place. If you were
the type to snatch away bread from children, your name would be
condemned from memory, forgotten.&lt;/p&gt;
&lt;h3 id="garbage-collection"&gt;Garbage-collection&lt;/h3&gt;
&lt;p&gt;The concept of &lt;em&gt;ren&lt;/em&gt; seems to be perfectly analogous to
reference counted garbage-collection.&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;A name (&lt;em&gt;ren&lt;/em&gt;) is assigned to an object (person) on
initialization (at birth)&lt;/li&gt;
&lt;li&gt;Names are used to refer to objects&lt;/li&gt;
&lt;li&gt;Objects go out of existence when there are no more references to
them&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;The concept of &lt;em&gt;ren&lt;/em&gt; seems to model human-memory. The
similarity with garbage-collection is now easily explained, because
garbage-collection models a program’s memory.&lt;/p&gt;
&lt;p&gt;Perhaps some cheeky Egyptian has attained immortality by creating a
&lt;em&gt;ren&lt;/em&gt;-cycle.&lt;/p&gt;</description>
<link>https://peppe.rs/posts/a_reference_counted_afterlife/</link>
<pubDate>Tue, 02 Aug 2022 16:47:00 +0000</pubDate>
<guid>https://peppe.rs/posts/a_reference_counted_afterlife/</guid>
</item>
<item>
<title>Lotus58</title>
<description>&lt;p&gt;Earlier this month, I decided that I would laugh at Indian customs in
the face by building a split-ergo mechanical keyboard from scratch
rather than purchasing a Moonlander.&lt;/p&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/i8k.jpg" alt="The finished product" /&gt;
&lt;figcaption aria-hidden="true"&gt;The finished product&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h2 id="sourcing-the-parts"&gt;Sourcing the parts&lt;/h2&gt;
&lt;p&gt;If you, like me, live in India, you might find this section useful.
My approach to finding parts:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;Check reputed, local online stores&lt;/li&gt;
&lt;li&gt;Check physical hardware stores&lt;/li&gt;
&lt;li&gt;Import the part&lt;/li&gt;
&lt;/ul&gt;
&lt;h3 id="pcbs"&gt;PCBs&lt;/h3&gt;
&lt;p&gt;This was by far the hardest component to procure. Fabrication
services have certain &lt;em&gt;capabilities&lt;/em&gt;. Capabilities are the
limitations of a fabrication service. For example, a service may be
capable of drilling holes no smaller than 0.3mm in diameter. Most sites
have a verification process to check if their capabilities meet your
design’s requirements. I tried a few local PCB fabrication services:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;Lion PCB: Capabilities did not meet my requirements&lt;/li&gt;
&lt;li&gt;PCBPower: Capabilities did not meet my requirements&lt;/li&gt;
&lt;li&gt;Circuitwala: Capabilities did not meet my requirements&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;I settled for JLCPCB, a Chinese service. PCBs themselves were 16 USD,
shipping was another 35 USD, and customs was another 3.5K INR
(ouch).&lt;/p&gt;
&lt;h3 id="case-material"&gt;Case material&lt;/h3&gt;
&lt;p&gt;I don’t really have a case for the Lotus58, it is more of a “plastic
sandwich”. I purchased acrylic plates from Robu. Cheap, fast, solid, and
customizable. I cannot recommend Robu enough. A full set of plates (2
top plates and 2 bottom plates) cost me about 500 INR. I also bought a
pair of laptop height raisers on Amazon to create a budget tenting
setup.&lt;/p&gt;
&lt;h3 id="electronics"&gt;Electronics&lt;/h3&gt;
&lt;p&gt;You’ll need a few rather specific electronic components such as
hotswap sockets and TRRS mounts, the rest are commonly available:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;Hotswap sockets: StacksKB&lt;/li&gt;
&lt;li&gt;TRRS mounts (PJ 320A): StacksKB&lt;/li&gt;
&lt;li&gt;Diodes (1N4841): StacksKB&lt;/li&gt;
&lt;li&gt;M2 screws: StacksKB&lt;/li&gt;
&lt;li&gt;M2 spacers: ThinkRobotics&lt;/li&gt;
&lt;li&gt;Arduino Pro Micro: Robu&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;I skimped out on optional components such as OLEDs and rotary
encoders.&lt;/p&gt;
&lt;h3 id="switches-and-keycaps"&gt;Switches and Keycaps&lt;/h3&gt;
&lt;p&gt;Arguably the most fun part of the build:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;Gateron Oil King switches: Rectangles&lt;/li&gt;
&lt;li&gt;DSA blanks: Meckeys&lt;/li&gt;
&lt;/ul&gt;
&lt;h2 id="building-the-keyboard"&gt;Building the keyboard&lt;/h2&gt;
&lt;p&gt;The the build is extremely straightforward. Through hole components
are easy to solder. Be wary of component placement and orientation.
Check thrice, solder once. Few debugging tips:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;if a single key does not actuate, check the hotswap for poor
soldering (reflow the joint), and the switch pins for deformation during
installation&lt;/li&gt;
&lt;li&gt;if an entire column or row activates on a single key-press, a
connection has been shorted&lt;/li&gt;
&lt;li&gt;if only some of the keys on a given row actuate, a diode has been
soldered on the wrong way&lt;/li&gt;
&lt;/ul&gt;
&lt;h2 id="the-typing-experience"&gt;The typing experience&lt;/h2&gt;
&lt;p&gt;I decidede to give QWERTY the boot and learn Colemak along with the
new keyboard. The first few weeks were terrible because I could neither
type QWERTY nor Colemak, but I got the hang of it pretty quickly. Typing
websites do help, but it is best to simply use it in your daily
workflow. No site can help you get accustomed to the various things you
use your keyboard for such as switching windows or navigating
vim/tmux.&lt;/p&gt;
&lt;h3 id="colemak"&gt;Colemak&lt;/h3&gt;
&lt;p&gt;Alt layouts such as Colemak are definitely worth it. I find that
Colemak reduces finger movement a lot, a good portion of the keys on the
left hand are the same as QWERTY, it is fairly easy to pick up as
well.&lt;/p&gt;
&lt;h3 id="vim"&gt;Vim&lt;/h3&gt;
&lt;p&gt;Using an alt layout means most programs with keyboard shortcuts are
not going to work as expected, &lt;code&gt;HJKL&lt;/code&gt; on vim for movements
being one of them. I took the short route out by creating a new layer
with arrow keys on the home row:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;default homerow:
H N E I

&amp;quot;nav&amp;quot; layer:
&amp;lt; v ^ &amp;gt;&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;The remaining commands in vim are largely mnemonics. Navigating with
home-row arrow keys also means that I can use “HJKL” globally, to scroll
a website, for example.&lt;/p&gt;
&lt;h3 id="cutting-down-to-34-keys"&gt;Cutting down to 34 keys&lt;/h3&gt;
&lt;p&gt;A couple months into my ergo journey, I realized that I could get
away by moving my fingers even lesser. I moved modifiers such as
&lt;code&gt;Super&lt;/code&gt;, &lt;code&gt;Ctrl&lt;/code&gt;, &lt;code&gt;Alt&lt;/code&gt; and
&lt;code&gt;Shift&lt;/code&gt; to the home-row as QMK Mod Taps. The rest of the keys
are cleverly placed in layers, not too much unlike the Miryoku layout.
Even for someone that writes Rust (a symbol-heavy grammar), I find
34-keys to be sufficient.&lt;/p&gt;
&lt;h2 id="conclusion"&gt;Conclusion&lt;/h2&gt;
&lt;p&gt;I have been bitten by the ergomech bug.&lt;/p&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/XM3.jpg" alt="The Lotus58 in action" /&gt;
&lt;figcaption aria-hidden="true"&gt;The Lotus58 in action&lt;/figcaption&gt;
&lt;/figure&gt;</description>
<link>https://peppe.rs/posts/lotus58/</link>
<pubDate>Mon, 13 Jun 2022 13:55:00 +0000</pubDate>
<guid>https://peppe.rs/posts/lotus58/</guid>
</item>
<item>
<title>Lightweight Linting</title>
<description>&lt;p&gt;&lt;a
href="https://tree-sitter.github.io/tree-sitter/using-parsers#pattern-matching-with-queries"&gt;Tree-sitter&lt;/a&gt;
queries allow you to search for patterns in syntax trees, much like a
regex would, in text. Combine that with some Rust glue to write simple,
custom linters.&lt;/p&gt;
&lt;h3 id="tree-sitter-syntax-trees"&gt;Tree-sitter syntax trees&lt;/h3&gt;
&lt;p&gt;Here is a quick crash course on syntax trees generated by
tree-sitter. Syntax trees produced by tree-sitter are represented by
S-expressions. The generated S-expression for the following Rust
code,&lt;/p&gt;
&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" tabindex="-1"&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;
&lt;span id="cb1-2"&gt;&lt;a href="#cb1-2" aria-hidden="true" tabindex="-1"&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;2&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-3"&gt;&lt;a href="#cb1-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;would be:&lt;/p&gt;
&lt;div class="sourceCode" id="cb2"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb2-1"&gt;&lt;a href="#cb2-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;(source_file&lt;/span&gt;
&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; (function_item&lt;/span&gt;
&lt;span id="cb2-3"&gt;&lt;a href="#cb2-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  name: (identifier)&lt;/span&gt;
&lt;span id="cb2-4"&gt;&lt;a href="#cb2-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  parameters: (parameters)&lt;/span&gt;
&lt;span id="cb2-5"&gt;&lt;a href="#cb2-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  body: &lt;/span&gt;
&lt;span id="cb2-6"&gt;&lt;a href="#cb2-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  (block&lt;/span&gt;
&lt;span id="cb2-7"&gt;&lt;a href="#cb2-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;   (let_declaration &lt;/span&gt;
&lt;span id="cb2-8"&gt;&lt;a href="#cb2-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    pattern: (identifier)&lt;/span&gt;
&lt;span id="cb2-9"&gt;&lt;a href="#cb2-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    value: (integer_literal)))))&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Syntax trees generated by tree-sitter have a couple of other cool
properties: they are &lt;em&gt;lossless&lt;/em&gt; syntax trees. Given a lossless
syntax tree, you can regenerate the original source code in its
entirety. Consider the following addition to our example:&lt;/p&gt;
&lt;div class="sourceCode" id="cb3"&gt;&lt;pre
class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb3-1"&gt;&lt;a href="#cb3-1" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb3-2"&gt;&lt;a href="#cb3-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt;    &lt;span class="co"&gt;// a comment goes here&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-3"&gt;&lt;a href="#cb3-3" aria-hidden="true" tabindex="-1"&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;2&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-4"&gt;&lt;a href="#cb3-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The tree-sitter syntax tree preserves the comment, while the typical
abstract syntax tree wouldn’t:&lt;/p&gt;
&lt;div class="sourceCode" id="cb4"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb4-1"&gt;&lt;a href="#cb4-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; (source_file&lt;/span&gt;
&lt;span id="cb4-2"&gt;&lt;a href="#cb4-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  (function_item&lt;/span&gt;
&lt;span id="cb4-3"&gt;&lt;a href="#cb4-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;   name: (identifier)&lt;/span&gt;
&lt;span id="cb4-4"&gt;&lt;a href="#cb4-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;   parameters: (parameters)&lt;/span&gt;
&lt;span id="cb4-5"&gt;&lt;a href="#cb4-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;   body:&lt;/span&gt;
&lt;span id="cb4-6"&gt;&lt;a href="#cb4-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;   (block&lt;/span&gt;
&lt;span id="cb4-7"&gt;&lt;a href="#cb4-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt;   (line_comment)&lt;/span&gt;
&lt;span id="cb4-8"&gt;&lt;a href="#cb4-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    (let_declaration&lt;/span&gt;
&lt;span id="cb4-9"&gt;&lt;a href="#cb4-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;     pattern: (identifier)&lt;/span&gt;
&lt;span id="cb4-10"&gt;&lt;a href="#cb4-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;     value: (integer_literal)))))&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h3 id="tree-sitter-queries"&gt;Tree-sitter queries&lt;/h3&gt;
&lt;p&gt;Tree-sitter provides a DSL to match over CSTs. These queries resemble
our S-expression syntax trees, here is a query to match all line
comments in a Rust CST:&lt;/p&gt;
&lt;div class="sourceCode" id="cb5"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb5-1"&gt;&lt;a href="#cb5-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;(line_comment)&lt;/span&gt;
&lt;span id="cb5-2"&gt;&lt;a href="#cb5-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb5-3"&gt;&lt;a href="#cb5-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; matches the following rust code&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb5-4"&gt;&lt;a href="#cb5-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; // a comment goes here&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Neat, eh? But don’t take my word for it, give it a go on the &lt;a
href="https://tree-sitter.github.io/tree-sitter/playground"&gt;tree-sitter
playground&lt;/a&gt;. Type in a query like so:&lt;/p&gt;
&lt;div class="sourceCode" id="cb6"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb6-1"&gt;&lt;a href="#cb6-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; the web playground requires you to specify a &amp;quot;capture&amp;quot;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb6-2"&gt;&lt;a href="#cb6-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; you will notice the capture and the nodes it captured&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb6-3"&gt;&lt;a href="#cb6-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; turn blue&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb6-4"&gt;&lt;a href="#cb6-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;(line_comment) @capture&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Here’s another to match &lt;code&gt;let&lt;/code&gt; expressions that bind an
integer to an identifier:&lt;/p&gt;
&lt;div class="sourceCode" id="cb7"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb7-1"&gt;&lt;a href="#cb7-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;(let_declaration&lt;/span&gt;
&lt;span id="cb7-2"&gt;&lt;a href="#cb7-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; pattern: (identifier)&lt;/span&gt;
&lt;span id="cb7-3"&gt;&lt;a href="#cb7-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; value: (integer_literal))&lt;/span&gt;
&lt;span id="cb7-4"&gt;&lt;a href="#cb7-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; &lt;/span&gt;
&lt;span id="cb7-5"&gt;&lt;a href="#cb7-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; matches:&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-6"&gt;&lt;a href="#cb7-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; let foo = 2;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;We can &lt;em&gt;capture&lt;/em&gt; nodes into variables:&lt;/p&gt;
&lt;div class="sourceCode" id="cb8"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb8-1"&gt;&lt;a href="#cb8-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;(let_declaration &lt;/span&gt;
&lt;span id="cb8-2"&gt;&lt;a href="#cb8-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; pattern: (identifier) @my-capture&lt;/span&gt;
&lt;span id="cb8-3"&gt;&lt;a href="#cb8-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; value: (integer_literal))&lt;/span&gt;
&lt;span id="cb8-4"&gt;&lt;a href="#cb8-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; &lt;/span&gt;
&lt;span id="cb8-5"&gt;&lt;a href="#cb8-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; matches:&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb8-6"&gt;&lt;a href="#cb8-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; let foo = 2;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb8-7"&gt;&lt;a href="#cb8-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb8-8"&gt;&lt;a href="#cb8-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; captures:&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb8-9"&gt;&lt;a href="#cb8-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; foo&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;And apply certain &lt;em&gt;predicates&lt;/em&gt; to captures:&lt;/p&gt;
&lt;div class="sourceCode" id="cb9"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb9-1"&gt;&lt;a href="#cb9-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;((let_declaration&lt;/span&gt;
&lt;span id="cb9-2"&gt;&lt;a href="#cb9-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  pattern: (identifier) @my-capture&lt;/span&gt;
&lt;span id="cb9-3"&gt;&lt;a href="#cb9-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  value: (integer_literal))&lt;/span&gt;
&lt;span id="cb9-4"&gt;&lt;a href="#cb9-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; (&lt;span class="sc"&gt;#e&lt;/span&gt;q? @my-capture &lt;span class="st"&gt;&amp;quot;foo&amp;quot;&lt;/span&gt;))&lt;/span&gt;
&lt;span id="cb9-5"&gt;&lt;a href="#cb9-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; &lt;/span&gt;
&lt;span id="cb9-6"&gt;&lt;a href="#cb9-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; matches:&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb9-7"&gt;&lt;a href="#cb9-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; let foo = 2;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb9-8"&gt;&lt;a href="#cb9-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb9-9"&gt;&lt;a href="#cb9-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; and not:&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb9-10"&gt;&lt;a href="#cb9-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; let bar = 2;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The &lt;code&gt;#match?&lt;/code&gt; predicate checks if a capture matches a
regex:&lt;/p&gt;
&lt;div class="sourceCode" id="cb10"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb10-1"&gt;&lt;a href="#cb10-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;((let_declaration&lt;/span&gt;
&lt;span id="cb10-2"&gt;&lt;a href="#cb10-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  pattern: (identifier) @my-capture&lt;/span&gt;
&lt;span id="cb10-3"&gt;&lt;a href="#cb10-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  value: (integer_literal))&lt;/span&gt;
&lt;span id="cb10-4"&gt;&lt;a href="#cb10-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; (#match? @my-capture &lt;span class="st"&gt;&amp;quot;foo|bar&amp;quot;&lt;/span&gt;))&lt;/span&gt;
&lt;span id="cb10-5"&gt;&lt;a href="#cb10-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; &lt;/span&gt;
&lt;span id="cb10-6"&gt;&lt;a href="#cb10-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; matches both `foo` and `bar`:&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb10-7"&gt;&lt;a href="#cb10-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; let foo = 2;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb10-8"&gt;&lt;a href="#cb10-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; let bar = 2;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Exhibit indifference, as a stoic programmer would, with the
&lt;em&gt;wildcard&lt;/em&gt; pattern:&lt;/p&gt;
&lt;div class="sourceCode" id="cb11"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb11-1"&gt;&lt;a href="#cb11-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;(let_declaration&lt;/span&gt;
&lt;span id="cb11-2"&gt;&lt;a href="#cb11-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; pattern: (identifier)&lt;/span&gt;
&lt;span id="cb11-3"&gt;&lt;a href="#cb11-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; value: (&lt;span class="op"&gt;_&lt;/span&gt;))&lt;/span&gt;
&lt;span id="cb11-4"&gt;&lt;a href="#cb11-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; &lt;/span&gt;
&lt;span id="cb11-5"&gt;&lt;a href="#cb11-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; matches:&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-6"&gt;&lt;a href="#cb11-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; let foo = &amp;quot;foo&amp;quot;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-7"&gt;&lt;a href="#cb11-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; let foo = 42;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-8"&gt;&lt;a href="#cb11-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;; let foo = bar;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;&lt;a
href="https://tree-sitter.github.io/tree-sitter/using-parsers#pattern-matching-with-queries"&gt;The
documentation&lt;/a&gt; does the tree-sitter query DSL more justice, but we
now know enough to write our first lint.&lt;/p&gt;
&lt;h3 id="write-you-a-tree-sitter-lint"&gt;Write you a tree-sitter lint&lt;/h3&gt;
&lt;p&gt;Strings in &lt;code&gt;std::env&lt;/code&gt; functions are error prone:&lt;/p&gt;
&lt;div class="sourceCode" id="cb12"&gt;&lt;pre
class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb12-1"&gt;&lt;a href="#cb12-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="pp"&gt;std::env::&lt;/span&gt;remove_var(&lt;span class="st"&gt;&amp;quot;RUST_BACKTACE&amp;quot;&lt;/span&gt;)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-2"&gt;&lt;a href="#cb12-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;                            &lt;span class="co"&gt;// ^^^^ &amp;quot;TACE&amp;quot; instead of &amp;quot;TRACE&amp;quot;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;I prefer this instead:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// somewhere in a module that is well spellchecked&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb13-2"&gt;&lt;a href="#cb13-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;static&lt;/span&gt; BACKTRACE&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="op"&gt;&amp;amp;&lt;/span&gt;&lt;span class="dt"&gt;str&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;RUST_BACKTRACE&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb13-3"&gt;&lt;a href="#cb13-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb13-4"&gt;&lt;a href="#cb13-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// rest of the codebase&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb13-5"&gt;&lt;a href="#cb13-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="pp"&gt;std::env::&lt;/span&gt;remove_var(BACKTRACE)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Let’s write a lint to find &lt;code&gt;std::env&lt;/code&gt; functions that use
strings. Put aside the effectiveness of this lint for the moment, and
take a stab at writing a tree-sitter query. For reference, a function
call like so:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;remove_var(&lt;span class="st"&gt;&amp;quot;RUST_BACKTRACE&amp;quot;&lt;/span&gt;)&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Produces the following S-expression:&lt;/p&gt;
&lt;div class="sourceCode" id="cb15"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb15-1"&gt;&lt;a href="#cb15-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;(call_expression&lt;/span&gt;
&lt;span id="cb15-2"&gt;&lt;a href="#cb15-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  function: (identifier)&lt;/span&gt;
&lt;span id="cb15-3"&gt;&lt;a href="#cb15-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  arguments: (arguments (string_literal)))&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;We are definitely looking for a &lt;code&gt;call_expression&lt;/code&gt;:&lt;/p&gt;
&lt;div class="sourceCode" id="cb16"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb16-1"&gt;&lt;a href="#cb16-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;(call_expression) @raise&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Whose function name matches &lt;code&gt;std::env::var&lt;/code&gt; or
&lt;code&gt;std::env::remove_var&lt;/code&gt; at the very least (I know, I know,
this isn’t the most optimal regex):&lt;/p&gt;
&lt;div class="sourceCode" id="cb17"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb17-1"&gt;&lt;a href="#cb17-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;((call_expression&lt;/span&gt;
&lt;span id="cb17-2"&gt;&lt;a href="#cb17-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  function: (&lt;span class="op"&gt;_&lt;/span&gt;) @fn-name) @raise&lt;/span&gt;
&lt;span id="cb17-3"&gt;&lt;a href="#cb17-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; (#match? @fn-name &lt;span class="st"&gt;&amp;quot;std::env::(var|remove_var)&amp;quot;&lt;/span&gt;))&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Let’s turn that &lt;code&gt;std::&lt;/code&gt; prefix optional:&lt;/p&gt;
&lt;div class="sourceCode" id="cb18"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb18-1"&gt;&lt;a href="#cb18-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;((call_expression&lt;/span&gt;
&lt;span id="cb18-2"&gt;&lt;a href="#cb18-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  function: (&lt;span class="op"&gt;_&lt;/span&gt;) @fn-name) @raise&lt;/span&gt;
&lt;span id="cb18-3"&gt;&lt;a href="#cb18-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; (#match? @fn-name &lt;span class="st"&gt;&amp;quot;(std::|)env::(var|remove_var)&amp;quot;&lt;/span&gt;))&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;And ensure that &lt;code&gt;arguments&lt;/code&gt; is a string:&lt;/p&gt;
&lt;div class="sourceCode" id="cb19"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb19-1"&gt;&lt;a href="#cb19-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;((call_expression&lt;/span&gt;
&lt;span id="cb19-2"&gt;&lt;a href="#cb19-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  function: (&lt;span class="op"&gt;_&lt;/span&gt;) @fn-name&lt;/span&gt;
&lt;span id="cb19-3"&gt;&lt;a href="#cb19-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  arguments: (arguments (string_literal)))&lt;/span&gt;
&lt;span id="cb19-4"&gt;&lt;a href="#cb19-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; (#match? @fn-name &lt;span class="st"&gt;&amp;quot;(std::|)env::(var|remove_var)&amp;quot;&lt;/span&gt;))&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h3 id="running-our-linter"&gt;Running our linter&lt;/h3&gt;
&lt;p&gt;We could always plug our query into the web playground, but let’s go
a step further:&lt;/p&gt;
&lt;div class="sourceCode" id="cb20"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb20-1"&gt;&lt;a href="#cb20-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;cargo&lt;/span&gt; new &lt;span class="at"&gt;--bin&lt;/span&gt; toy-lint&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Add &lt;code&gt;tree-sitter&lt;/code&gt; and &lt;code&gt;tree-sitter-rust&lt;/code&gt; to
your dependencies:&lt;/p&gt;
&lt;div class="sourceCode" id="cb21"&gt;&lt;pre
class="sourceCode toml"&gt;&lt;code class="sourceCode toml"&gt;&lt;span id="cb21-1"&gt;&lt;a href="#cb21-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# within Cargo.toml&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb21-2"&gt;&lt;a href="#cb21-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;[&lt;/span&gt;&lt;span class="dt"&gt;dependencies&lt;/span&gt;&lt;span class="kw"&gt;]&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb21-3"&gt;&lt;a href="#cb21-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="dt"&gt;tree-sitter&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;0.20&amp;quot;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb21-4"&gt;&lt;a href="#cb21-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb21-5"&gt;&lt;a href="#cb21-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;[&lt;/span&gt;&lt;span class="dt"&gt;dependencies&lt;/span&gt;&lt;span class="kw"&gt;.&lt;/span&gt;&lt;span class="dt"&gt;tree-sitter-rust&lt;/span&gt;&lt;span class="kw"&gt;]&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb21-6"&gt;&lt;a href="#cb21-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="dt"&gt;git&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;https://github.com/tree-sitter/tree-sitter-rust&amp;quot;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Let’s load in some Rust code to work with. As &lt;a
href="https://en.wikipedia.org/wiki/Self-reference"&gt;an ode to Gödel&lt;/a&gt;
(G&lt;code&gt;ode&lt;/code&gt;l?), why not load in our linter itself:&lt;/p&gt;
&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" tabindex="-1"&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;
&lt;span id="cb22-2"&gt;&lt;a href="#cb22-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="kw"&gt;let&lt;/span&gt; src &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="pp"&gt;include_str!&lt;/span&gt;(&lt;span class="st"&gt;&amp;quot;main.rs&amp;quot;&lt;/span&gt;)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb22-3"&gt;&lt;a href="#cb22-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Most tree-sitter APIs require a reference to a &lt;code&gt;Language&lt;/code&gt;
struct, we will be working with Rust if you haven’t already guessed:&lt;/p&gt;
&lt;div class="sourceCode" id="cb23"&gt;&lt;pre
class="sourceCode rust"&gt;&lt;code class="sourceCode rust"&gt;&lt;span id="cb23-1"&gt;&lt;a href="#cb23-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;tree_sitter::&lt;/span&gt;Language&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb23-2"&gt;&lt;a href="#cb23-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb23-3"&gt;&lt;a href="#cb23-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; rust_lang&lt;span class="op"&gt;:&lt;/span&gt; Language &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="pp"&gt;tree_sitter_rust::&lt;/span&gt;language()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Enough scaffolding, let’s parse some Rust:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;tree_sitter::&lt;/span&gt;Parser&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb24-2"&gt;&lt;a href="#cb24-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb24-3"&gt;&lt;a href="#cb24-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; &lt;span class="kw"&gt;mut&lt;/span&gt; parser &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="pp"&gt;Parser::&lt;/span&gt;new()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb24-4"&gt;&lt;a href="#cb24-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;parser&lt;span class="op"&gt;.&lt;/span&gt;set_language(rust_lang)&lt;span class="op"&gt;.&lt;/span&gt;unwrap()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb24-5"&gt;&lt;a href="#cb24-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb24-6"&gt;&lt;a href="#cb24-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; parse_tree &lt;span class="op"&gt;=&lt;/span&gt; parser&lt;span class="op"&gt;.&lt;/span&gt;parse(&lt;span class="op"&gt;&amp;amp;&lt;/span&gt;src&lt;span class="op"&gt;,&lt;/span&gt; &lt;span class="cn"&gt;None&lt;/span&gt;)&lt;span class="op"&gt;.&lt;/span&gt;unwrap()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The second argument to &lt;code&gt;Parser::parse&lt;/code&gt; may be of interest.
Tree-sitter has this cool feature that allows for quick reparsing of
existing parse trees if they contain edits. If you do happen to want to
reparse a source file, you can pass in the old tree:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// if you wish to reparse instead of parse&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb25-2"&gt;&lt;a href="#cb25-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;old_tree&lt;span class="op"&gt;.&lt;/span&gt;edit(&lt;span class="co"&gt;/* redacted */&lt;/span&gt;)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb25-3"&gt;&lt;a href="#cb25-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb25-4"&gt;&lt;a href="#cb25-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// generate shiny new reparsed tree&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb25-5"&gt;&lt;a href="#cb25-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; new_tree &lt;span class="op"&gt;=&lt;/span&gt; parser&lt;span class="op"&gt;.&lt;/span&gt;parse(&lt;span class="op"&gt;&amp;amp;&lt;/span&gt;src&lt;span class="op"&gt;,&lt;/span&gt; &lt;span class="cn"&gt;Some&lt;/span&gt;(old_tree))&lt;span class="op"&gt;.&lt;/span&gt;unwrap()&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Anyhow (&lt;a href="http://github.com/dtolnay/anyhow"&gt;hah!&lt;/a&gt;), now
that we have a parse tree, we can inspect it:&lt;/p&gt;
&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" tabindex="-1"&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; parse_tree&lt;span class="op"&gt;.&lt;/span&gt;root_node()&lt;span class="op"&gt;.&lt;/span&gt;to_sexp())&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Or better yet, run a query on it:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;tree_sitter::&lt;/span&gt;Query&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb27-2"&gt;&lt;a href="#cb27-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb27-3"&gt;&lt;a href="#cb27-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; query &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="pp"&gt;Query::&lt;/span&gt;new(&lt;/span&gt;
&lt;span id="cb27-4"&gt;&lt;a href="#cb27-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    rust_lang&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb27-5"&gt;&lt;a href="#cb27-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="st"&gt;r#&amp;quot;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb27-6"&gt;&lt;a href="#cb27-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="st"&gt;    ((call_expression&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb27-7"&gt;&lt;a href="#cb27-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="st"&gt;      function: (_) @fn-name&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb27-8"&gt;&lt;a href="#cb27-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="st"&gt;      arguments: (arguments (string_literal))) @raise&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb27-9"&gt;&lt;a href="#cb27-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="st"&gt;     (#match? @fn-name &amp;quot;(std::|)env::(var|remove_var)&amp;quot;))&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb27-10"&gt;&lt;a href="#cb27-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="st"&gt;    &amp;quot;#&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb27-11"&gt;&lt;a href="#cb27-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;)&lt;/span&gt;
&lt;span id="cb27-12"&gt;&lt;a href="#cb27-12" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;.&lt;/span&gt;unwrap()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;A &lt;code&gt;QueryCursor&lt;/code&gt; is tree-sitter’s way of maintaining state
as we iterate through the matches or captures produced by running a
query on the parse tree. Observe:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;use&lt;/span&gt; &lt;span class="pp"&gt;tree_sitter::&lt;/span&gt;QueryCursor&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb28-2"&gt;&lt;a href="#cb28-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb28-3"&gt;&lt;a href="#cb28-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; &lt;span class="kw"&gt;mut&lt;/span&gt; query_cursor &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="pp"&gt;QueryCursor::&lt;/span&gt;new()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb28-4"&gt;&lt;a href="#cb28-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; all_matches &lt;span class="op"&gt;=&lt;/span&gt; query_cursor&lt;span class="op"&gt;.&lt;/span&gt;matches(&lt;/span&gt;
&lt;span id="cb28-5"&gt;&lt;a href="#cb28-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="op"&gt;&amp;amp;&lt;/span&gt;query&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb28-6"&gt;&lt;a href="#cb28-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    parse_tree&lt;span class="op"&gt;.&lt;/span&gt;root_node()&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb28-7"&gt;&lt;a href="#cb28-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    src&lt;span class="op"&gt;.&lt;/span&gt;as_bytes()&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb28-8"&gt;&lt;a href="#cb28-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;We begin by passing our query to the cursor, followed by the “root
node”, which is another way of saying, “start from the top”, and lastly,
the source itself. If you have already taken a look at the C API, you
will notice that the last argument, the source (known as the
&lt;code&gt;TextProvider&lt;/code&gt;), is not required. The Rust bindings seem to
require this argument to provide predicate functionality such as
&lt;code&gt;#match?&lt;/code&gt; and &lt;code&gt;#eq?&lt;/code&gt;.&lt;/p&gt;
&lt;p&gt;Do something with the matches:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// get the index of the capture named &amp;quot;raise&amp;quot;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-2"&gt;&lt;a href="#cb29-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; raise_idx &lt;span class="op"&gt;=&lt;/span&gt; query&lt;span class="op"&gt;.&lt;/span&gt;capture_index_for_name(&lt;span class="st"&gt;&amp;quot;raise&amp;quot;&lt;/span&gt;)&lt;span class="op"&gt;.&lt;/span&gt;unwrap()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-3"&gt;&lt;a href="#cb29-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb29-4"&gt;&lt;a href="#cb29-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="cf"&gt;for&lt;/span&gt; each_match &lt;span class="kw"&gt;in&lt;/span&gt; all_matches &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-5"&gt;&lt;a href="#cb29-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="co"&gt;// iterate over all captures called &amp;quot;raise&amp;quot;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-6"&gt;&lt;a href="#cb29-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="co"&gt;// ignore captures such as &amp;quot;fn-name&amp;quot;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-7"&gt;&lt;a href="#cb29-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="cf"&gt;for&lt;/span&gt; capture &lt;span class="kw"&gt;in&lt;/span&gt; each_match&lt;/span&gt;
&lt;span id="cb29-8"&gt;&lt;a href="#cb29-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        &lt;span class="op"&gt;.&lt;/span&gt;captures&lt;/span&gt;
&lt;span id="cb29-9"&gt;&lt;a href="#cb29-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        &lt;span class="op"&gt;.&lt;/span&gt;iter()&lt;/span&gt;
&lt;span id="cb29-10"&gt;&lt;a href="#cb29-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        &lt;span class="op"&gt;.&lt;/span&gt;filter(&lt;span class="op"&gt;|&lt;/span&gt;c&lt;span class="op"&gt;|&lt;/span&gt; c&lt;span class="op"&gt;.&lt;/span&gt;idx &lt;span class="op"&gt;==&lt;/span&gt; raise_idx)&lt;/span&gt;
&lt;span id="cb29-11"&gt;&lt;a href="#cb29-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-12"&gt;&lt;a href="#cb29-12" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        &lt;span class="kw"&gt;let&lt;/span&gt; range &lt;span class="op"&gt;=&lt;/span&gt; capture&lt;span class="op"&gt;.&lt;/span&gt;node&lt;span class="op"&gt;.&lt;/span&gt;range()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-13"&gt;&lt;a href="#cb29-13" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        &lt;span class="kw"&gt;let&lt;/span&gt; text &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;&amp;amp;&lt;/span&gt;src[range&lt;span class="op"&gt;.&lt;/span&gt;start_byte&lt;span class="op"&gt;..&lt;/span&gt;range&lt;span class="op"&gt;.&lt;/span&gt;end_byte]&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-14"&gt;&lt;a href="#cb29-14" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        &lt;span class="kw"&gt;let&lt;/span&gt; line &lt;span class="op"&gt;=&lt;/span&gt; range&lt;span class="op"&gt;.&lt;/span&gt;start_point&lt;span class="op"&gt;.&lt;/span&gt;row&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-15"&gt;&lt;a href="#cb29-15" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        &lt;span class="kw"&gt;let&lt;/span&gt; col &lt;span class="op"&gt;=&lt;/span&gt; range&lt;span class="op"&gt;.&lt;/span&gt;start_point&lt;span class="op"&gt;.&lt;/span&gt;column&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-16"&gt;&lt;a href="#cb29-16" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        &lt;span class="pp"&gt;println!&lt;/span&gt;(&lt;/span&gt;
&lt;span id="cb29-17"&gt;&lt;a href="#cb29-17" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;            &lt;span class="st"&gt;&amp;quot;[Line: {}, Col: {}] Offending source code: `{}`&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-18"&gt;&lt;a href="#cb29-18" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;            line&lt;span class="op"&gt;,&lt;/span&gt; col&lt;span class="op"&gt;,&lt;/span&gt; text&lt;/span&gt;
&lt;span id="cb29-19"&gt;&lt;a href="#cb29-19" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        )&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-20"&gt;&lt;a href="#cb29-20" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-21"&gt;&lt;a href="#cb29-21" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Lastly, add the following line to your source code, to get the linter
to catch something:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="pp"&gt;env::&lt;/span&gt;remove_var(&lt;span class="st"&gt;&amp;quot;RUST_BACKTRACE&amp;quot;&lt;/span&gt;)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;And &lt;code&gt;cargo run&lt;/code&gt;:&lt;/p&gt;
&lt;pre class="shell"&gt;&lt;code&gt;λ cargo run
   Compiling toy-lint v0.1.0 (/redacted/path/to/toy-lint)
    Finished dev [unoptimized + debuginfo] target(s) in 0.74s
     Running `target/debug/toy-lint`
[Line: 40, Col: 4] Offending source code: `env::remove_var(&amp;quot;RUST_BACKTRACE&amp;quot;)`&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Thank you tree-sitter!&lt;/p&gt;
&lt;h3 id="bonus"&gt;Bonus&lt;/h3&gt;
&lt;p&gt;Keen readers will notice that I avoided
&lt;code&gt;std::env::set_var&lt;/code&gt;. Because &lt;code&gt;set_var&lt;/code&gt; is called
with two arguments, a “key” and a “value”, unlike &lt;code&gt;env::var&lt;/code&gt;
and &lt;code&gt;env::remove_var&lt;/code&gt;. As a result, it requires more
juggling:&lt;/p&gt;
&lt;div class="sourceCode" id="cb32"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb32-1"&gt;&lt;a href="#cb32-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;((call_expression&lt;/span&gt;
&lt;span id="cb32-2"&gt;&lt;a href="#cb32-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  function: (&lt;span class="op"&gt;_&lt;/span&gt;) @fn-name&lt;/span&gt;
&lt;span id="cb32-3"&gt;&lt;a href="#cb32-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  arguments: (arguments &lt;span class="op"&gt;.&lt;/span&gt; (string_literal)&lt;span class="op"&gt;?&lt;/span&gt; &lt;span class="op"&gt;.&lt;/span&gt; (string_literal) &lt;span class="op"&gt;.&lt;/span&gt;)) @raise&lt;/span&gt;
&lt;span id="cb32-4"&gt;&lt;a href="#cb32-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; (#match? @fn-name &lt;span class="st"&gt;&amp;quot;(std::|)env::(var|remove_var|set_var)&amp;quot;&lt;/span&gt;))&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The interesting part of this query is the humble &lt;code&gt;.&lt;/code&gt;, the
&lt;em&gt;anchor&lt;/em&gt; operator. Anchors help constrain child nodes in certain
ways. In this case, it ensures that we match exactly two
&lt;code&gt;string_literal&lt;/code&gt;s who are siblings or exactly one
&lt;code&gt;string_literal&lt;/code&gt; with no siblings. Unfortunately, this query
also matches the following invalid Rust code:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// remove_var accepts only 1 arg!&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb33-2"&gt;&lt;a href="#cb33-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="pp"&gt;std::env::&lt;/span&gt;remove_var(&lt;span class="st"&gt;&amp;quot;RUST_BACKTRACE&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;1&amp;quot;&lt;/span&gt;)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h3 id="notes"&gt;Notes&lt;/h3&gt;
&lt;p&gt;All-in-all, the query DSL does a great job in lowering the bar to
writing language tools. The knowledge gained from mastering the query
DSL can be applied to other languages that have tree-sitter grammars
too. This query detects &lt;code&gt;to_json&lt;/code&gt; methods that do not accept
additional arguments, in Ruby:&lt;/p&gt;
&lt;div class="sourceCode" id="cb34"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb34-1"&gt;&lt;a href="#cb34-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;((method&lt;/span&gt;
&lt;span id="cb34-2"&gt;&lt;a href="#cb34-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  name: (identifier) @fn&lt;/span&gt;
&lt;span id="cb34-3"&gt;&lt;a href="#cb34-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  !parameters)&lt;/span&gt;
&lt;span id="cb34-4"&gt;&lt;a href="#cb34-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; (&lt;span class="sc"&gt;#i&lt;/span&gt;s? @fn &lt;span class="st"&gt;&amp;quot;to_json&amp;quot;&lt;/span&gt;))&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;</description>
<link>https://peppe.rs/posts/lightweight_linting/</link>
<pubDate>Wed, 26 Jan 2022 12:52:00 +0000</pubDate>
<guid>https://peppe.rs/posts/lightweight_linting/</guid>
</item>
<item>
<title>Novice Nix: Flake Templates</title>
<description>&lt;p&gt;Flakes are very handy to setup entirely pure, project-specific
dependencies (not just dependencies, but build steps, shell environments
and more) in a declarative way. Writing Flake expressions can get
repetitive though, oftentimes, you’d much rather start off with a
skeleton. Luckily, &lt;code&gt;nix&lt;/code&gt; already supports templates!&lt;/p&gt;
&lt;p&gt;You might already be familiar with &lt;code&gt;nix flake init&lt;/code&gt;, that
drops a “default” flake expression into your current working directory.
If you head over to the manpage:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;nix&lt;/span&gt; flake init &lt;span class="at"&gt;--help&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;You will read that &lt;code&gt;nix flake init&lt;/code&gt; creates a flake using
the “default template”. Additionally, you can create a flake from a
specific template by passing the &lt;code&gt;-t&lt;/code&gt; flag. Where does this
default originate from?&lt;/p&gt;
&lt;h2 id="flake-registries"&gt;Flake Registries&lt;/h2&gt;
&lt;p&gt;Quick detour into registries! Registries are a way to alias popular
flakes using identifiers:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# list a few predefined registries&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix registry list&lt;/span&gt;
&lt;span id="cb2-3"&gt;&lt;a href="#cb2-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="bu"&gt;.&lt;/span&gt; . . &lt;/span&gt;
&lt;span id="cb2-4"&gt;&lt;a href="#cb2-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;global&lt;/span&gt; flake:nixpkgs github:NixOS/nixpkgs&lt;/span&gt;
&lt;span id="cb2-5"&gt;&lt;a href="#cb2-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;global&lt;/span&gt; flake:patchelf github:NixOS/patchelf&lt;/span&gt;
&lt;span id="cb2-6"&gt;&lt;a href="#cb2-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;global&lt;/span&gt; flake:nix-serve github:edolstra/nix-serve&lt;/span&gt;
&lt;span id="cb2-7"&gt;&lt;a href="#cb2-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;global&lt;/span&gt; flake:templates github:NixOS/templates&lt;/span&gt;
&lt;span id="cb2-8"&gt;&lt;a href="#cb2-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;global&lt;/span&gt; flake:nickel github:tweag/nickel&lt;/span&gt;
&lt;span id="cb2-9"&gt;&lt;a href="#cb2-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="bu"&gt;.&lt;/span&gt; . .&lt;/span&gt;
&lt;span id="cb2-10"&gt;&lt;a href="#cb2-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb2-11"&gt;&lt;a href="#cb2-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# you can do &lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-12"&gt;&lt;a href="#cb2-12" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix flake show nickel&lt;/span&gt;
&lt;span id="cb2-13"&gt;&lt;a href="#cb2-13" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb2-14"&gt;&lt;a href="#cb2-14" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# instead of &lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-15"&gt;&lt;a href="#cb2-15" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix flake show github:tweag/nickel&lt;/span&gt;
&lt;span id="cb2-16"&gt;&lt;a href="#cb2-16" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb2-17"&gt;&lt;a href="#cb2-17" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# which is short for&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-18"&gt;&lt;a href="#cb2-18" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix flake show git+https://github.com/tweag/nickel&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;You might notice a registry called &lt;code&gt;templates&lt;/code&gt; aliased to
&lt;code&gt;github:NixOS/templates&lt;/code&gt;. Take a peek with
&lt;code&gt;nix flake show&lt;/code&gt;:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix flake show templates&lt;/span&gt;
&lt;span id="cb3-2"&gt;&lt;a href="#cb3-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;github:NixOS/templates/79f48a7b822f35c068c5e235da2e9fbd154cecee&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-3"&gt;&lt;a href="#cb3-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;├───defaultTemplate:&lt;/span&gt; template: A very basic flake&lt;/span&gt;
&lt;span id="cb3-4"&gt;&lt;a href="#cb3-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;└───templates&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-5"&gt;&lt;a href="#cb3-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="ex"&gt;├───bash-hello:&lt;/span&gt; template: An over-engineered Hello World in bash&lt;/span&gt;
&lt;span id="cb3-6"&gt;&lt;a href="#cb3-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="ex"&gt;├───c-hello:&lt;/span&gt; template: An over-engineered Hello World in C&lt;/span&gt;
&lt;span id="cb3-7"&gt;&lt;a href="#cb3-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="ex"&gt;├───rust-web-server:&lt;/span&gt; template: A Rust web server including a NixOS module&lt;/span&gt;
&lt;span id="cb3-8"&gt;&lt;a href="#cb3-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="ex"&gt;├───simpleContainer:&lt;/span&gt; template: A NixOS container running apache-httpd&lt;/span&gt;
&lt;span id="cb3-9"&gt;&lt;a href="#cb3-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="ex"&gt;└───trivial:&lt;/span&gt; template: A very basic flake&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Aha! There is a flake output called &lt;code&gt;defaultTemplate&lt;/code&gt;.
This is the template being sourced when you run
&lt;code&gt;nix flake init&lt;/code&gt;. Astute readers may conclude the
following:&lt;/p&gt;
&lt;div class="sourceCode" id="cb4"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb4-1"&gt;&lt;a href="#cb4-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix flake init&lt;/span&gt;
&lt;span id="cb4-2"&gt;&lt;a href="#cb4-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb4-3"&gt;&lt;a href="#cb4-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# is equivalent to&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb4-4"&gt;&lt;a href="#cb4-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix flake init &lt;span class="at"&gt;-t&lt;/span&gt; templates#defaultTemplate&lt;/span&gt;
&lt;span id="cb4-5"&gt;&lt;a href="#cb4-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb4-6"&gt;&lt;a href="#cb4-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# is equivalent to&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb4-7"&gt;&lt;a href="#cb4-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix flake init &lt;span class="at"&gt;-t&lt;/span&gt; github:NixOS/templates#defaultTemplate&lt;/span&gt;
&lt;span id="cb4-8"&gt;&lt;a href="#cb4-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb4-9"&gt;&lt;a href="#cb4-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# which is short for&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb4-10"&gt;&lt;a href="#cb4-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix flake init &lt;span class="at"&gt;-t&lt;/span&gt; git+https://github.com/NixOS/templates#defaultTemplate&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Similarly, the other templates can be accessed via:&lt;/p&gt;
&lt;div class="sourceCode" id="cb5"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb5-1"&gt;&lt;a href="#cb5-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix flake init &lt;span class="at"&gt;-t&lt;/span&gt; templates#c-hello&lt;/span&gt;
&lt;span id="cb5-2"&gt;&lt;a href="#cb5-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix flake init &lt;span class="at"&gt;-t&lt;/span&gt; templates#simpleContainer&lt;/span&gt;
&lt;span id="cb5-3"&gt;&lt;a href="#cb5-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# I think you get the drift ...&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h2 id="rolling-your-own-templates"&gt;Rolling your own templates&lt;/h2&gt;
&lt;p&gt;Alright, so all we need to do is:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;create a flake with a &lt;code&gt;templates&lt;/code&gt; output&lt;/li&gt;
&lt;li&gt;populate our template directories with content&lt;/li&gt;
&lt;li&gt;(&lt;strong&gt;optionally&lt;/strong&gt;) alias our custom templates flake to an
identifier using registries, for easier access&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;Start off by creating a directory to store your templates in (we will
be converting this to a registry later):&lt;/p&gt;
&lt;div class="sourceCode" id="cb6"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb6-1"&gt;&lt;a href="#cb6-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; mkdir ~/mytemplates&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;A flake that exposes a “template” as its output looks something like
this:&lt;/p&gt;
&lt;div class="sourceCode" id="cb7"&gt;&lt;pre
class="sourceCode nix"&gt;&lt;code class="sourceCode nix"&gt;&lt;span id="cb7-1"&gt;&lt;a href="#cb7-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# inside ~/mytemplates/flake.nix&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-2"&gt;&lt;a href="#cb7-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb7-3"&gt;&lt;a href="#cb7-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-4"&gt;&lt;a href="#cb7-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="va"&gt;description&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;Pepper&amp;#39;s flake templates&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-5"&gt;&lt;a href="#cb7-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb7-6"&gt;&lt;a href="#cb7-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="va"&gt;outputs&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt; &lt;span class="va"&gt;self&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 class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-7"&gt;&lt;a href="#cb7-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="va"&gt;templates&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-8"&gt;&lt;a href="#cb7-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;      &lt;span class="va"&gt;latex-report&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-9"&gt;&lt;a href="#cb7-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        &lt;span class="va"&gt;path&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="ss"&gt;./latex-report-template&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-10"&gt;&lt;a href="#cb7-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        &lt;span class="va"&gt;description&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;A latex whitepaper project&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-11"&gt;&lt;a href="#cb7-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;      &lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-12"&gt;&lt;a href="#cb7-12" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;      &lt;span class="va"&gt;rust-hello&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-13"&gt;&lt;a href="#cb7-13" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        &lt;span class="va"&gt;path&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="ss"&gt;./rust-hello-template&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-14"&gt;&lt;a href="#cb7-14" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        &lt;span class="va"&gt;description&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;Simple Hello World in Rust&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-15"&gt;&lt;a href="#cb7-15" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;      &lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-16"&gt;&lt;a href="#cb7-16" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-17"&gt;&lt;a href="#cb7-17" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-18"&gt;&lt;a href="#cb7-18" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The &lt;code&gt;path&lt;/code&gt; attribute to each template is what gets copied
over when you initialize a flake. Running
&lt;code&gt;nix flake init -t .#latex-report&lt;/code&gt; will initialize the
current directory with the contents of
&lt;code&gt;./latex-report-template&lt;/code&gt; (we are yet to populate these
directories).&lt;/p&gt;
&lt;p&gt;The output of &lt;code&gt;nix flake show&lt;/code&gt; should be something
like:&lt;/p&gt;
&lt;div class="sourceCode" id="cb8"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb8-1"&gt;&lt;a href="#cb8-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix flake show&lt;/span&gt;
&lt;span id="cb8-2"&gt;&lt;a href="#cb8-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;path:/home/np/code/nix-stuff/template-tests?narHash=sha256-{...}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb8-3"&gt;&lt;a href="#cb8-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;└───templates&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb8-4"&gt;&lt;a href="#cb8-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="ex"&gt;├───latex-report:&lt;/span&gt; template: A latex whitepaper project&lt;/span&gt;
&lt;span id="cb8-5"&gt;&lt;a href="#cb8-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="ex"&gt;└───rust-hello:&lt;/span&gt; template: Simple Hello World in Rust&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Populate your template directories with content, here are my template
directories for example:&lt;/p&gt;
&lt;div class="sourceCode" id="cb9"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb9-1"&gt;&lt;a href="#cb9-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; tree mytemplates&lt;/span&gt;
&lt;span id="cb9-2"&gt;&lt;a href="#cb9-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;mytemplates/&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb9-3"&gt;&lt;a href="#cb9-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;├──&lt;/span&gt; flake.nix&lt;/span&gt;
&lt;span id="cb9-4"&gt;&lt;a href="#cb9-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;├──&lt;/span&gt; latex-report-template&lt;/span&gt;
&lt;span id="cb9-5"&gt;&lt;a href="#cb9-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│  &lt;/span&gt; ├── flake.nix&lt;/span&gt;
&lt;span id="cb9-6"&gt;&lt;a href="#cb9-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│  &lt;/span&gt; ├── makefile&lt;/span&gt;
&lt;span id="cb9-7"&gt;&lt;a href="#cb9-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│  &lt;/span&gt; └── src&lt;/span&gt;
&lt;span id="cb9-8"&gt;&lt;a href="#cb9-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│  &lt;/span&gt;     ├── meta.sty&lt;/span&gt;
&lt;span id="cb9-9"&gt;&lt;a href="#cb9-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;│  &lt;/span&gt;     └── report.tex&lt;/span&gt;
&lt;span id="cb9-10"&gt;&lt;a href="#cb9-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;└──&lt;/span&gt; rust-hello-template&lt;/span&gt;
&lt;span id="cb9-11"&gt;&lt;a href="#cb9-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="ex"&gt;├──&lt;/span&gt; Cargo.toml&lt;/span&gt;
&lt;span id="cb9-12"&gt;&lt;a href="#cb9-12" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="ex"&gt;├──&lt;/span&gt; flake.nix&lt;/span&gt;
&lt;span id="cb9-13"&gt;&lt;a href="#cb9-13" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="ex"&gt;└──&lt;/span&gt; src&lt;/span&gt;
&lt;span id="cb9-14"&gt;&lt;a href="#cb9-14" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        &lt;span class="ex"&gt;└──&lt;/span&gt; main.rs&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;And that’s it! Start using your templates with:&lt;/p&gt;
&lt;div class="sourceCode" id="cb10"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb10-1"&gt;&lt;a href="#cb10-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix flake init &lt;span class="at"&gt;-t&lt;/span&gt; ~/mytemplates#rust-hello&lt;/span&gt;
&lt;span id="cb10-2"&gt;&lt;a href="#cb10-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; tree .&lt;/span&gt;
&lt;span id="cb10-3"&gt;&lt;a href="#cb10-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="bu"&gt;.&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb10-4"&gt;&lt;a href="#cb10-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;├──&lt;/span&gt; Cargo.toml&lt;/span&gt;
&lt;span id="cb10-5"&gt;&lt;a href="#cb10-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;├──&lt;/span&gt; flake.nix&lt;/span&gt;
&lt;span id="cb10-6"&gt;&lt;a href="#cb10-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;└──&lt;/span&gt; src&lt;/span&gt;
&lt;span id="cb10-7"&gt;&lt;a href="#cb10-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="ex"&gt;└──&lt;/span&gt; main.rs&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;To avoid writing &lt;code&gt;~/mytemplates&lt;/code&gt; each time, simply alias
it to a registry:&lt;/p&gt;
&lt;div class="sourceCode" id="cb11"&gt;&lt;pre
class="sourceCode bash"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb11-1"&gt;&lt;a href="#cb11-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# alias it to `biscuits`&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-2"&gt;&lt;a href="#cb11-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix registry add biscuits ~/mytemplates&lt;/span&gt;
&lt;span id="cb11-3"&gt;&lt;a href="#cb11-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb11-4"&gt;&lt;a href="#cb11-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# you will see it listed under `user` registries&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-5"&gt;&lt;a href="#cb11-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix registry list&lt;/span&gt;
&lt;span id="cb11-6"&gt;&lt;a href="#cb11-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="bu"&gt;.&lt;/span&gt; . .&lt;/span&gt;
&lt;span id="cb11-7"&gt;&lt;a href="#cb11-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;user&lt;/span&gt;   flake:biscuits path:/home/np/template-tests&lt;/span&gt;
&lt;span id="cb11-8"&gt;&lt;a href="#cb11-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="bu"&gt;.&lt;/span&gt; . .&lt;/span&gt;
&lt;span id="cb11-9"&gt;&lt;a href="#cb11-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb11-10"&gt;&lt;a href="#cb11-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="ex"&gt;$&lt;/span&gt; nix flake init &lt;span class="at"&gt;-t&lt;/span&gt; biscuits#latex-report&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h2 id="extending-the-official-templates"&gt;Extending the official
templates&lt;/h2&gt;
&lt;p&gt;I personally, would like the &lt;code&gt;biscuits&lt;/code&gt; registry to
include not just my homemade templates, but also the templates from
&lt;code&gt;NixOS/templates&lt;/code&gt; (and maybe a couple of other repositories
in the wild):&lt;/p&gt;
&lt;div class="sourceCode" id="cb12"&gt;&lt;pre
class="sourceCode nix"&gt;&lt;code class="sourceCode nix"&gt;&lt;span id="cb12-1"&gt;&lt;a href="#cb12-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-2"&gt;&lt;a href="#cb12-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;   &lt;span class="va"&gt;description&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;Pepper&amp;#39;s flake templates&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-3"&gt;&lt;a href="#cb12-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; &lt;/span&gt;
&lt;span id="cb12-4"&gt;&lt;a href="#cb12-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;+  &lt;span class="va"&gt;inputs&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-5"&gt;&lt;a href="#cb12-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;+    &lt;span class="va"&gt;official-templates&lt;/span&gt;.&lt;span class="va"&gt;url&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="va"&gt;github&lt;/span&gt;&lt;span class="op"&gt;:&lt;/span&gt;&lt;span class="ss"&gt;NixOS/templates&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-6"&gt;&lt;a href="#cb12-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;+    &lt;span class="va"&gt;other-templates&lt;/span&gt;.&lt;span class="va"&gt;url&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="va"&gt;github&lt;/span&gt;&lt;span class="op"&gt;:&lt;/span&gt;&lt;span class="ss"&gt;some-other/templates&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-7"&gt;&lt;a href="#cb12-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;+  &lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-8"&gt;&lt;a href="#cb12-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; &lt;/span&gt;
&lt;span id="cb12-9"&gt;&lt;a href="#cb12-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;   &lt;span class="va"&gt;outputs&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt; &lt;span class="va"&gt;self&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; &lt;span class="va"&gt;official-templates&lt;/span&gt;&lt;span class="op"&gt;,&lt;/span&gt; &lt;span class="va"&gt;other-templates&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;span id="cb12-10"&gt;&lt;a href="#cb12-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; &lt;/span&gt;
&lt;span id="cb12-11"&gt;&lt;a href="#cb12-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;     &lt;span class="va"&gt;templates&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-12"&gt;&lt;a href="#cb12-12" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;       &lt;span class="va"&gt;latex-report&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-13"&gt;&lt;a href="#cb12-13" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;         &lt;span class="va"&gt;path&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="ss"&gt;./latex-report-template&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-14"&gt;&lt;a href="#cb12-14" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;         &lt;span class="va"&gt;description&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;A latex whitepaper project&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-15"&gt;&lt;a href="#cb12-15" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;       &lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-16"&gt;&lt;a href="#cb12-16" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;       &lt;span class="va"&gt;rust-hello&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-17"&gt;&lt;a href="#cb12-17" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;         &lt;span class="va"&gt;path&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="ss"&gt;./rust-hello-template&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-18"&gt;&lt;a href="#cb12-18" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;         &lt;span class="va"&gt;description&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;Simple Hello World in Rust, with overloaded Rust toolchain&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-19"&gt;&lt;a href="#cb12-19" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;       &lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-20"&gt;&lt;a href="#cb12-20" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;     &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-21"&gt;&lt;a href="#cb12-21" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt;    &lt;span class="op"&gt;//&lt;/span&gt; official&lt;span class="op"&gt;-&lt;/span&gt;templates.templates&lt;/span&gt;
&lt;span id="cb12-22"&gt;&lt;a href="#cb12-22" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt;    &lt;span class="op"&gt;//&lt;/span&gt; other&lt;span class="op"&gt;-&lt;/span&gt;templates.templates&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-23"&gt;&lt;a href="#cb12-23" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; &lt;/span&gt;
&lt;span id="cb12-24"&gt;&lt;a href="#cb12-24" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;   &lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb12-25"&gt;&lt;a href="#cb12-25" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Running &lt;code&gt;nix flake show biscuits&lt;/code&gt; will now list templates
from the &lt;code&gt;biscuits&lt;/code&gt; registry as well as the ones from
&lt;code&gt;NixOS/templates&lt;/code&gt;. Ensure that the names don’t collide
though.&lt;/p&gt;</description>
<link>https://peppe.rs/posts/novice_nix:_flake_templates/</link>
<pubDate>Tue, 05 Oct 2021 16:49:00 +0000</pubDate>
<guid>https://peppe.rs/posts/novice_nix:_flake_templates/</guid>
</item>
<item>
<title>SDL2 Devlog</title>
<description>&lt;p&gt;I have been working on an editor for the &lt;a
href="https://git.peppe.rs/graphics/obi/about"&gt;One Bit Image&lt;/a&gt; file
format in Rust and SDL2. This entry in my blog follows my progress on
the editor. The days are listed in reverse chronological order, begin
from the bottom, if this is your first time on this page.&lt;/p&gt;
&lt;h3 id="day-20"&gt;Day 20&lt;/h3&gt;
&lt;p&gt;More &lt;code&gt;lisp&lt;/code&gt; stuff! I added a new brush, for rectangular
selections. While selection doesn’t do much on its own, the selected
area can be passed onto a &lt;code&gt;lisp&lt;/code&gt; procedure, for example, a
procedure to draw horizontal black and white lines:&lt;/p&gt;
&lt;figure&gt;
&lt;video src="https://u.peppe.rs/frU.mp4" controls=""&gt;&lt;a
href="https://u.peppe.rs/frU.mp4"&gt;Day 20&lt;/a&gt;&lt;/video&gt;
&lt;figcaption aria-hidden="true"&gt;Day 20&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-19"&gt;Day 19&lt;/h3&gt;
&lt;p&gt;Attempted &lt;a href="https://peppe.rs/art/conduit.png"&gt;some isometric
art&lt;/a&gt; within the editor. The angles displayed alongside the line brush
are handly, however, having only a rectangular grid did not help. I
implemented an isometric grid today. Isometric grids in pixel art differ
in that the tangent of the isometric angle is exactly 0.5! For every
pixel down, you go exactly two pixels sideways. The math works out
really well in the drawing procedures too, dealing with floating points
is a pain.&lt;/p&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/1Kb.png" alt="Day 19" /&gt;
&lt;figcaption aria-hidden="true"&gt;Day 19&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-18"&gt;Day 18&lt;/h3&gt;
&lt;p&gt;I added basic support for guides, they can be added and activated
from the &lt;code&gt;lisp&lt;/code&gt; REPL. Another long standing improvement I
wanted to make was reworking the pixmap drawing procedure. The old
procedure draws a square for each pixel in the pixmap, coloured
according to its value in the pixmap. Naturally, this means, for an
&lt;strong&gt;NxN&lt;/strong&gt; pixmap, there are &lt;strong&gt;N²&lt;/strong&gt; calls to SDL!
I reworked this procedure to compress each line of the pixmap using RLE
(run length encoding), and call out to SDL for each run in the line.
This drastically improved drawing speeds on larger grids. The following
is a comparison between the two procedures, the leftmost picture is the
rendered image, the middle picture is the optimized drawing procedure
(draws each run instead of pixel), and the right most picture is the
primitive drawing procedure (draws each pixel):&lt;/p&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/U4B.png" alt="Day 18" /&gt;
&lt;figcaption aria-hidden="true"&gt;Day 18&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-17"&gt;Day 17&lt;/h3&gt;
&lt;p&gt;I decided to give the text-only statusline a touch up, by adding a
active color and dither level preview. Aligning the “widget” to the
right of statusline involved a lot more than I thought, so I created a
ghetto CSS-like rectangle placement system to position containers inside
containers:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// roughly something like this&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-2"&gt;&lt;a href="#cb1-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; statusline &lt;span class="op"&gt;=&lt;/span&gt; &lt;/span&gt;
&lt;span id="cb1-3"&gt;&lt;a href="#cb1-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="pp"&gt;Container::&lt;/span&gt;new(&lt;span class="pp"&gt;Offset::&lt;/span&gt;Left(&lt;span class="dv"&gt;0&lt;/span&gt;)&lt;span class="op"&gt;,&lt;/span&gt; &lt;span class="pp"&gt;Offset::&lt;/span&gt;Bottom(&lt;span class="dv"&gt;40&lt;/span&gt;))&lt;/span&gt;
&lt;span id="cb1-4"&gt;&lt;a href="#cb1-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="op"&gt;.&lt;/span&gt;width(&lt;span class="pp"&gt;Size::&lt;/span&gt;Max)&lt;/span&gt;
&lt;span id="cb1-5"&gt;&lt;a href="#cb1-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="op"&gt;.&lt;/span&gt;height(&lt;span class="pp"&gt;Size::&lt;/span&gt;Absolute(&lt;span class="dv"&gt;20&lt;/span&gt;))&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-6"&gt;&lt;a href="#cb1-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;/span&gt;
&lt;span id="cb1-7"&gt;&lt;a href="#cb1-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; &lt;span class="kw"&gt;mut&lt;/span&gt; primary &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="pp"&gt;Container::&lt;/span&gt;uninit()&lt;/span&gt;
&lt;span id="cb1-8"&gt;&lt;a href="#cb1-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="op"&gt;.&lt;/span&gt;width(&lt;span class="pp"&gt;Size::&lt;/span&gt;Absolute(&lt;span class="dv"&gt;16&lt;/span&gt;))&lt;/span&gt;
&lt;span id="cb1-9"&gt;&lt;a href="#cb1-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="op"&gt;.&lt;/span&gt;height(&lt;span class="pp"&gt;Size::&lt;/span&gt;Absolute(&lt;span class="dv"&gt;16&lt;/span&gt;))&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-10"&gt;&lt;a href="#cb1-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;/span&gt;
&lt;span id="cb1-11"&gt;&lt;a href="#cb1-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;container&lt;span class="op"&gt;.&lt;/span&gt;place(&lt;/span&gt;
&lt;span id="cb1-12"&gt;&lt;a href="#cb1-12" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="op"&gt;&amp;amp;&lt;/span&gt;&lt;span class="kw"&gt;mut&lt;/span&gt; padding_box&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-13"&gt;&lt;a href="#cb1-13" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="pp"&gt;HorAlign::&lt;/span&gt;Right&lt;span class="op"&gt;,&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-14"&gt;&lt;a href="#cb1-14" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="pp"&gt;VertAlign::&lt;/span&gt;Center&lt;/span&gt;
&lt;span id="cb1-15"&gt;&lt;a href="#cb1-15" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The result (brush preview on the bottom right):&lt;/p&gt;
&lt;figure&gt;
&lt;video src="https://u.peppe.rs/OtU.mp4" controls=""&gt;&lt;a
href="https://u.peppe.rs/OtU.mp4"&gt;Day 17&lt;/a&gt;&lt;/video&gt;
&lt;figcaption aria-hidden="true"&gt;Day 17&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-16"&gt;Day 16&lt;/h3&gt;
&lt;p&gt;The embedded lisp is coming along nicely, users can load a custom
&lt;code&gt;rc.lisp&lt;/code&gt;, which is evaluated on startup. To disable to grid
on start, for example:&lt;/p&gt;
&lt;div class="sourceCode" id="cb2"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb2-1"&gt;&lt;a href="#cb2-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;;;; rc.lisp&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;(toggle-grid)&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Some aliases to switch between brushes:&lt;/p&gt;
&lt;div class="sourceCode" id="cb3"&gt;&lt;pre
class="sourceCode scheme"&gt;&lt;code class="sourceCode scheme"&gt;&lt;span id="cb3-1"&gt;&lt;a href="#cb3-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;;;; rc.lisp&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-2"&gt;&lt;a href="#cb3-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;(&lt;span class="ex"&gt;define&lt;/span&gt;&lt;span class="fu"&gt; &lt;/span&gt;(brush kind)&lt;/span&gt;
&lt;span id="cb3-3"&gt;&lt;a href="#cb3-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  (&lt;span class="kw"&gt;cond&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-4"&gt;&lt;a href="#cb3-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    ((&lt;span class="kw"&gt;eq?&lt;/span&gt; kind &amp;#39;f) (brush-fill))&lt;/span&gt;
&lt;span id="cb3-5"&gt;&lt;a href="#cb3-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    ((&lt;span class="kw"&gt;eq?&lt;/span&gt; kind &amp;#39;c) (brush-circle))&lt;/span&gt;
&lt;span id="cb3-6"&gt;&lt;a href="#cb3-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    ((&lt;span class="kw"&gt;eq?&lt;/span&gt; kind &amp;#39;l) (brush-line))&lt;/span&gt;
&lt;span id="cb3-7"&gt;&lt;a href="#cb3-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    ((&lt;span class="kw"&gt;eq?&lt;/span&gt; kind &amp;#39;l+) (brush-line-extend))&lt;/span&gt;
&lt;span id="cb3-8"&gt;&lt;a href="#cb3-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    (&lt;span class="kw"&gt;else&lt;/span&gt; (brush-circle))))&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The following script draws a straight line along a given axis, at a
given distance from the canvas boundary:&lt;/p&gt;
&lt;figure&gt;
&lt;video src="https://u.peppe.rs/b3i.mp4" controls=""&gt;&lt;a
href="https://u.peppe.rs/b3i.mp4"&gt;Day 16&lt;/a&gt;&lt;/video&gt;
&lt;figcaption aria-hidden="true"&gt;Day 16&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-15"&gt;Day 15&lt;/h3&gt;
&lt;p&gt;I began writing a standard library for the lisp, in lisp. It includes
basic list operations: &lt;code&gt;car&lt;/code&gt;, &lt;code&gt;cdr&lt;/code&gt;,
&lt;code&gt;null?&lt;/code&gt;, &lt;code&gt;list&lt;/code&gt;, higher order functions:
&lt;code&gt;map&lt;/code&gt;, &lt;code&gt;filter&lt;/code&gt;, &lt;code&gt;fold&lt;/code&gt;:&lt;/p&gt;
&lt;div class="sourceCode" id="cb4"&gt;&lt;pre
class="sourceCode lisp"&gt;&lt;code class="sourceCode commonlisp"&gt;&lt;span id="cb4-1"&gt;&lt;a href="#cb4-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;(define (member? item ls)&lt;/span&gt;
&lt;span id="cb4-2"&gt;&lt;a href="#cb4-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  (fold &lt;span class="dv"&gt;#f&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb4-3"&gt;&lt;a href="#cb4-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        (&lt;span class="kw"&gt;lambda&lt;/span&gt; (acc x) (&lt;span class="kw"&gt;or&lt;/span&gt; acc (eq? item x)))&lt;/span&gt;
&lt;span id="cb4-4"&gt;&lt;a href="#cb4-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        ls))&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h3 id="day-14"&gt;Day 14&lt;/h3&gt;
&lt;p&gt;I attempted a &lt;a href="https://peppe.rs/art/ramen_noodles.png"&gt;small
art piece&lt;/a&gt; using the editor, while it was largely usable, I felt a
certain lack of feedback. The brushes just didn’t relay as much info as
I’d have liked, for example, the approximate points of the line or the
angle made by the line against the x-axis. Unfortunately, the existing
infrastructure around brushes and line drawing didn’t easily allow for
this either. I went ahead and reimplemented brushes, and added a new
flood fill brush too:&lt;/p&gt;
&lt;figure&gt;
&lt;video src="https://u.peppe.rs/8q.mp4" controls=""&gt;&lt;a
href="https://u.peppe.rs/8q.mp4"&gt;Day 14&lt;/a&gt;&lt;/video&gt;
&lt;figcaption aria-hidden="true"&gt;Day 14&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-13"&gt;Day 13&lt;/h3&gt;
&lt;p&gt;I added a few more forms to the &lt;code&gt;lisp&lt;/code&gt; evaluator. It
handles recursion, definitions, variable mutation and more. The prelude
contains 20 subroutines so far, including comparision and logic
operators. The REPL interface on the SDL side requires some UX tweaks;
environment based completion, readline motions sound doable.&lt;/p&gt;
&lt;figure&gt;
&lt;video src="https://u.peppe.rs/u3.mp4" controls=""&gt;&lt;a
href="https://u.peppe.rs/u3.mp4"&gt;Day 13&lt;/a&gt;&lt;/video&gt;
&lt;figcaption aria-hidden="true"&gt;Day 13&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-12"&gt;Day 12&lt;/h3&gt;
&lt;p&gt;I lifted most of &lt;a
href="https://github.com/murarth/ketos"&gt;murarth/ketos&lt;/a&gt; into the
editor. &lt;code&gt;ketos&lt;/code&gt;’s implementation of &lt;code&gt;lisp&lt;/code&gt; is too
vast for my use case. For example, the editor does not need data types
to handle raw strings or byte strings. I have got a basic evaluator
running inside the SDL2 context (notice the &lt;code&gt;lisp&lt;/code&gt; REPL at
the bottom of the window). Over the following days, I intend to create a
set of prelude functions to manipulate the pixmap. Users can implement
their own brushes, dithering patterns, keybinds and more
(hopefully).&lt;/p&gt;
&lt;figure&gt;
&lt;video src="https://u.peppe.rs/y0.mp4" controls=""&gt;&lt;a
href="https://u.peppe.rs/y0.mp4"&gt;Day 12&lt;/a&gt;&lt;/video&gt;
&lt;figcaption aria-hidden="true"&gt;Day 12&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-11"&gt;Day 11&lt;/h3&gt;
&lt;p&gt;I intend to supplement the editor with scripting language and an
inbuilt REPL for the same. I began by implementing a text box widget
from scratch, with history and readline like editing:&lt;/p&gt;
&lt;figure&gt;
&lt;video src="https://u.peppe.rs/Mh.mp4" controls=""&gt;&lt;a
href="https://u.peppe.rs/Mh.mp4"&gt;Day 11&lt;/a&gt;&lt;/video&gt;
&lt;figcaption aria-hidden="true"&gt;Day 11&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-10"&gt;Day 10&lt;/h3&gt;
&lt;p&gt;I started reading up on dithering methods and half-toning, I wanted
to create a dithering brush that would automatically produce popular
dithering patterns. The method that caught my eye (and also the one used
most often in pixel art), was Bayer’s ordered dithering. When applied to
a black and white image, each pixel, based on its intensity, is mapped
to a 4x4 grid of pixels. A completely empty (completely black) 4x4 grid
represents zero intensity, and a filled 4x4 grid represents full
intensity. Bayer’s ordered dithering can produce 15 steps of intensity
between zero and full (by switching on exactly 1 pixel more at each
level), thus, being able to draw 17 “shades” from white to black.
Creating a dithering brush from here was fairly trivial. Our pixmap is
supposed to represent the final dithered image, it must be divided into
4x4 grids. Each grid is colored based on the intensity of the brush
passing over it:&lt;/p&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/Mn.png" alt="Day 10" /&gt;
&lt;figcaption aria-hidden="true"&gt;Day 10&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-9"&gt;Day 9&lt;/h3&gt;
&lt;p&gt;I started working towards an interface. I like the idea of a largely
read-only HUD, i. e., an interface that simply describes the state of
the application. Changes to this state are initiated via keybinds or
text commands. I am proud of the symmetry indicator; &lt;code&gt;-&lt;/code&gt; for
horizontal symmetry, &lt;code&gt;|&lt;/code&gt; for vertical symmetry,
&lt;code&gt;+&lt;/code&gt; for radial symmetry.&lt;/p&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/hx.png" alt="Day 9" /&gt;
&lt;figcaption aria-hidden="true"&gt;Day 9&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-8"&gt;Day 8&lt;/h3&gt;
&lt;p&gt;One of my favourite features of GIMP was symmetric editing. I added
some coordinate geometry primitives to my pixmap abstraction, allowing
for mirroring and reflecting figures about lines or points. The result
was an ergonomic function that applies symmetry to any painting
operation, (undo/redo works as expected):&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; line &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;self&lt;/span&gt;&lt;span class="op"&gt;.&lt;/span&gt;pixmap&lt;span class="op"&gt;.&lt;/span&gt;get_line(start&lt;span class="op"&gt;,&lt;/span&gt; end)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb5-2"&gt;&lt;a href="#cb5-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;let&lt;/span&gt; sym_line &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="kw"&gt;self&lt;/span&gt;&lt;span class="op"&gt;.&lt;/span&gt;symmetry&lt;span class="op"&gt;.&lt;/span&gt;apply(&lt;span class="op"&gt;&amp;amp;&lt;/span&gt;line)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb5-3"&gt;&lt;a href="#cb5-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="cf"&gt;for&lt;/span&gt; point on line&lt;span class="op"&gt;.&lt;/span&gt;extend(sym_line) &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb5-4"&gt;&lt;a href="#cb5-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="co"&gt;// draw to window&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb5-5"&gt;&lt;a href="#cb5-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;figure&gt;
&lt;video src="https://u.peppe.rs/B1.mp4" controls=""&gt;&lt;a
href="https://u.peppe.rs/B1.mp4"&gt;Day 8&lt;/a&gt;&lt;/video&gt;
&lt;figcaption aria-hidden="true"&gt;Day 8&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-7"&gt;Day 7&lt;/h3&gt;
&lt;p&gt;Bresenham saves the day again! This time, I implemented his line
drawing algorithm, to, well, draw lines. Each point on the line is then
“buffed” based on the active brush size. Today’s changes fit in very
well with the undo system and the brush size feature. Creating the right
abstractions, one at a time :)&lt;/p&gt;
&lt;figure&gt;
&lt;video src="https://u.peppe.rs/xt.mp4" controls=""&gt;&lt;a
href="https://u.peppe.rs/xt.mp4"&gt;Day 7&lt;/a&gt;&lt;/video&gt;
&lt;figcaption aria-hidden="true"&gt;Day 7&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-6"&gt;Day 6&lt;/h3&gt;
&lt;p&gt;I extended Bresenham’s algorithm to draw not just circle outlines,
but also generate their fills. Unlike Bresenham’s algorithm, this
variant generates points for two quadrants at once, these points are
mirrored over the dividing axis to generate the other two quadrants.&lt;/p&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/f3.png" alt="Day 6" /&gt;
&lt;figcaption aria-hidden="true"&gt;Day 6&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-5"&gt;Day 5&lt;/h3&gt;
&lt;p&gt;I discovered and implemented Bresenham’s algorithm for efficient
circle drawing. The algorithm allowed for sized circular brushes,
something I really liked from GIMP. Very convenient that the Wikipedia
page for Bresenham’s algorithm also includes a section about optimizing
for integer based arithmetic. I managed to abstract out another giant
component of the application, the pixmap. Any image is just a grid of
pixels (a pixmap), where the pixel’s value is decided by the application
(1-bit in my case). I could potentially extend the application to a
24-bit image editor!&lt;/p&gt;
&lt;figure&gt;
&lt;video src="https://u.peppe.rs/Kh.mp4" controls=""&gt;&lt;a
href="https://u.peppe.rs/Kh.mp4"&gt;Day 5&lt;/a&gt;&lt;/video&gt;
&lt;figcaption aria-hidden="true"&gt;Day 5&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-4"&gt;Day 4&lt;/h3&gt;
&lt;p&gt;I created a generic “undo stack” data structure that allows for
infinite “undos” and “redos”. Every modification operation to the grid
is persisted to the application state. A couple of keybinds allow the
user to revert and re-apply these operations! I expect abstracting this
component will come in handy down the line.&lt;/p&gt;
&lt;figure&gt;
&lt;video src="https://u.peppe.rs/w5.mp4" controls=""&gt;&lt;a
href="https://u.peppe.rs/w5.mp4"&gt;Day 4&lt;/a&gt;&lt;/video&gt;
&lt;figcaption aria-hidden="true"&gt;Day 4&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-3"&gt;Day 3&lt;/h3&gt;
&lt;p&gt;I implemented the bare minimum required to call the program an
“editor”. The application displays a grid, tracks mouse events, paints
white to the canvas on left click, and black to the canvas on right
click. I created a make-shift MVC architecture à la Elm in Rust.&lt;/p&gt;
&lt;figure&gt;
&lt;video src="https://u.peppe.rs/GF.mp4" controls=""&gt;&lt;a
href="https://u.peppe.rs/GF.mp4"&gt;Day 3&lt;/a&gt;&lt;/video&gt;
&lt;figcaption aria-hidden="true"&gt;Day 3&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-2"&gt;Day 2&lt;/h3&gt;
&lt;p&gt;I started figuring out event handling today. Implemented a couple of
keybinds to zoom in/out of the drawing area. Conversions of SDL2
coordinates (measured in signed 32 bit integers) to my internal “drawing
area” coordinates (measured in unsigned 32 bit integers) is very
annoying. Hopefully the unchecked conversions won’t haunt me later.&lt;/p&gt;
&lt;figure&gt;
&lt;video src="https://u.peppe.rs/L4.mp4" controls=""&gt;&lt;a
href="https://u.peppe.rs/L4.mp4"&gt;Day 2&lt;/a&gt;&lt;/video&gt;
&lt;figcaption aria-hidden="true"&gt;Day 2&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;h3 id="day-1"&gt;Day 1&lt;/h3&gt;
&lt;p&gt;Getting started with Rust and SDL2 is very straightforward. The
&lt;code&gt;rust-sdl2&lt;/code&gt; library contains some detailed examples that
allowed me to get all the way to drawing a grid from a
&lt;code&gt;Vec&amp;lt;bool&amp;gt;&lt;/code&gt;:&lt;/p&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/Ma.png" alt="Day 1" /&gt;
&lt;figcaption aria-hidden="true"&gt;Day 1&lt;/figcaption&gt;
&lt;/figure&gt;</description>
<link>https://peppe.rs/posts/SDL2_devlog/</link>
<pubDate>Sun, 11 Apr 2021 10:46:00 +0000</pubDate>
<guid>https://peppe.rs/posts/SDL2_devlog/</guid>
</item>
<item>
<title>Self-hosting Git</title>
<description>&lt;p&gt;Earlier this week, I began migrating my repositories from Github to
&lt;a href="https://git.zx2c4.com/cgit/about/"&gt;cgit&lt;/a&gt;. If you care at all
about big corporates turning open-source into a T-shirt farming service,
this is the way to go.&lt;/p&gt;
&lt;h3 id="offerings"&gt;Offerings&lt;/h3&gt;
&lt;p&gt;cgit is &lt;em&gt;very&lt;/em&gt; bare bones. It is &lt;a
href="https://tools.ietf.org/html/rfc3875"&gt;cgi-based&lt;/a&gt; web interface
to git, and nothing more. You may browse repositories, view diffs,
commit logs and even clone via http. If you are looking to replace
Github with cgit, keep in mind that cgit does not handle issues or
pull/merge requests. If people wish to contribute to your work, they
would have to send you a patch via email.&lt;/p&gt;
&lt;h3 id="setup"&gt;Setup&lt;/h3&gt;
&lt;p&gt;Installing cgit is fairly straightforward, if you would like to
compile it from source:&lt;/p&gt;
&lt;div class="sourceCode" id="cb1"&gt;&lt;pre class="sourceCode sh"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb1-1"&gt;&lt;a href="#cb1-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# fetch&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-2"&gt;&lt;a href="#cb1-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="fu"&gt;git&lt;/span&gt; clone https://git.zx2c4.com &lt;span class="kw"&gt;&amp;amp;&amp;amp;&lt;/span&gt; &lt;span class="bu"&gt;cd&lt;/span&gt; cgit&lt;/span&gt;
&lt;span id="cb1-3"&gt;&lt;a href="#cb1-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="fu"&gt;git&lt;/span&gt; submodule init&lt;/span&gt;
&lt;span id="cb1-4"&gt;&lt;a href="#cb1-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="fu"&gt;git&lt;/span&gt; submodule update&lt;/span&gt;
&lt;span id="cb1-5"&gt;&lt;a href="#cb1-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb1-6"&gt;&lt;a href="#cb1-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# install&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-7"&gt;&lt;a href="#cb1-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="fu"&gt;make&lt;/span&gt; NO_LUA=1&lt;/span&gt;
&lt;span id="cb1-8"&gt;&lt;a href="#cb1-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="fu"&gt;sudo&lt;/span&gt; make install&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;This would drop the cgit cgi script (and the default css) into
&lt;code&gt;/var/www/htdocs/cgit&lt;/code&gt;. You may configure cgit by editing
&lt;code&gt;/etc/cgitrc&lt;/code&gt;. I specify the &lt;code&gt;NO_LUA&lt;/code&gt; flag to
compile without lua support, exclude that flag if you would like to
extend cgit via lua scripts.&lt;/p&gt;
&lt;h3 id="going-live"&gt;Going live&lt;/h3&gt;
&lt;p&gt;You might want to use, &lt;a
href="https://github.com/gnosek/fcgiwrap"&gt;fcgiwrap&lt;/a&gt;, a &lt;a
href="http://www.nongnu.org/fastcgi"&gt;fastcgi&lt;/a&gt; wrapper for
&lt;code&gt;cgi&lt;/code&gt; scripts,&lt;/p&gt;
&lt;div class="sourceCode" id="cb2"&gt;&lt;pre class="sourceCode sh"&gt;&lt;code class="sourceCode bash"&gt;&lt;span id="cb2-1"&gt;&lt;a href="#cb2-1" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="fu"&gt;sudo&lt;/span&gt; apt install fcgiwrap&lt;/span&gt;
&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="fu"&gt;sudo&lt;/span&gt; systemctl start fcgiwrap.socket&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Expose the cgit cgi script to the web via &lt;code&gt;nginx&lt;/code&gt;:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;# nginx.conf
server {
  listen 80;
  server_name git.example.com;

  # serve static files
  location ~* ^.+\.(css|png|ico)$ {
    root /var/www/htdocs/cgit;
  }

  location / {
    fastcgi_pass  unix:/run/fcgiwrap.socket;
    fastcgi_param SCRIPT_FILENAME /var/www/htdocs/cgit/cgit.cgi; # the default location of the cgit cgi script
    fastcgi_param PATH_INFO       $uri;
    fastcgi_param QUERY_STRING    $args;
  }
}&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Point cgit to your git repositories:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;# /etc/cgitrc
scan-path=/path/to/git/repos&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;&lt;strong&gt;&lt;em&gt;Note&lt;/em&gt;&lt;/strong&gt;: &lt;em&gt;&lt;code&gt;scan-path&lt;/code&gt; works best
if you stick it at the end of your &lt;code&gt;cgitrc&lt;/code&gt;&lt;/em&gt;.&lt;/p&gt;
&lt;p&gt;You may now create remote repositories at
&lt;code&gt;/path/to/git/repos&lt;/code&gt;, via:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;git init --bare&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Add the remote to your local repository:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;git remote set-url origin user@remote:/above/path
git push origin master&lt;/code&gt;&lt;/pre&gt;
&lt;h3 id="configuration"&gt;Configuration&lt;/h3&gt;
&lt;p&gt;cgit is fairly easy to configure, all configuration options can be
found &lt;a href="https://git.zx2c4.com/cgit/tree/cgitrc.5.txt"&gt;in the
manual&lt;/a&gt;, here are a couple of cool ones though:&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;enable-commit-graph&lt;/strong&gt;: Generates a text based
graphical representation of the commit history, similar to
&lt;code&gt;git log --graph --oneline&lt;/code&gt;.&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;| * |    Add support for configuration file
* | |    simplify command parsing logic
* | |    Refactor parsers
* | |    Add basic tests
* | |    Merge remote-tracking branch &amp;#39;origin/master&amp;#39; in...
|\| |
| * |    add installation instructions for nix
| * |    switch to pancurses backendv0.2.2
| * |    bump to v0.2.2
* | |    Merge branch &amp;#39;master&amp;#39; into feature/larger-names...
|\| |
| * |    enable feature based compilation to support win...
| * |    remove dependency on rustc v1.45, bump to v0.2....
| * |      Merge branch &amp;#39;feature/windows&amp;#39; of https://git...
| |\ \
| | * |    add windows to github actions
| | * |    switch to crossterm backend
| | * |      Merge branch &amp;#39;fix/duplicate-habits&amp;#39;
| | |\ \
| | | * |    move duplicate check to command parsing blo...&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;&lt;strong&gt;section-from-path&lt;/strong&gt;: This option paired with
&lt;code&gt;scan-path&lt;/code&gt; will automatically generate sections in your cgit
index page, from the path to each repo. For example, the directory
structure used to generate sections on &lt;a href="https://git.peppe.rs"&gt;my
cgit instance&lt;/a&gt; looks like this:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;├── cli
│   ├── dijo
│   ├── eva
│   ├── pista
│   ├── taizen
│   └── xcursorlocate
├── config
│   ├── dotfiles
│   └── nixos
├── fonts
│   ├── curie
│   └── scientifica
├── languages
│   └── lisk
├── libs
│   ├── cutlass
│   └── fondant
├── terminfo
├── university
│   └── furby
└── web
    └── isostatic&lt;/code&gt;&lt;/pre&gt;
&lt;h3 id="ease-of-use"&gt;Ease of use&lt;/h3&gt;
&lt;p&gt;As I mentioned before, &lt;code&gt;cgit&lt;/code&gt; is simply a view into your
git repositories, you will have to manually create new repositories by
entering your remote and using &lt;code&gt;git init --bare&lt;/code&gt;. Here are a
couple of scripts I wrote to perform actions on remotes, think of it as
a smaller version of Github’s &lt;code&gt;gh&lt;/code&gt; program.&lt;/p&gt;
&lt;p&gt;You may save these scripts as &lt;code&gt;git-script-name&lt;/code&gt; and drop
them in your &lt;code&gt;$PATH&lt;/code&gt;, and git will automatically add an alias
called &lt;code&gt;script-name&lt;/code&gt;, callable via:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;git script-name&lt;/code&gt;&lt;/pre&gt;
&lt;h4 id="git-new-repo"&gt;git-new-repo&lt;/h4&gt;
&lt;p&gt;Creates a new repository on your remote, the first arg may be a path
(section/repo-name) or just the repo name:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;#! /usr/bin/env bash
#
# usage:
# git new-repo section/repo-name
# 
# example:
# git new-repo fonts/scientifica
# creates: user@remote:fonts/scientifica

if [ $# -eq 0 ]; then
    echo &amp;quot;requires an arg&amp;quot;
    exit 1
fi

ssh user@remote git init --bare &amp;quot;$1&amp;quot;;&lt;/code&gt;&lt;/pre&gt;
&lt;h4 id="git-set-desc"&gt;git-set-desc&lt;/h4&gt;
&lt;p&gt;To set a one line repository description. It simply copies the local
&lt;code&gt;.git/description&lt;/code&gt;, into &lt;code&gt;remote/description&lt;/code&gt;.
&lt;code&gt;cgit&lt;/code&gt; displays the contents of this file on the index
page:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;#! /usr/bin/env bash
#
# usage:
# enter repo description into .git/description and run:
# git set-desc 

remote=$(git remote get-url --push origin)
scp .git/description &amp;quot;$remote/description&amp;quot;&lt;/code&gt;&lt;/pre&gt;</description>
<link>https://peppe.rs/posts/self-hosting_git/</link>
<pubDate>Sat, 17 Oct 2020 07:04:00 +0000</pubDate>
<guid>https://peppe.rs/posts/self-hosting_git/</guid>
</item>
<item>
<title>NixOS</title>
<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;
&lt;h3 id="installation"&gt;Installation&lt;/h3&gt;
&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;
&lt;h3 id="setup"&gt;Setup&lt;/h3&gt;
&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;
&lt;pre&gt;&lt;code&gt;{
    server.xserver.libinput.enable = true;  # touchpad
    programs.light.enable = true;           # backlight
    hardware.pulseaudio.enable = true;      # audio
    networking.wireless.enable = true;      # wifi
}&lt;/code&gt;&lt;/pre&gt;
&lt;h3 id="developing-with-nix"&gt;Developing with Nix&lt;/h3&gt;
&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;
&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;
&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;
&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;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;#! /usr/bin/env nix-shell&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;#! nix-shell -i bash -p eva pandoc esh&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-3"&gt;&lt;a href="#cb2-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb2-4"&gt;&lt;a href="#cb2-4" aria-hidden="true" tabindex="-1"&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;
&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;
&lt;h3 id="impressions"&gt;Impressions&lt;/h3&gt;
&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;
&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;
&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;
&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>
<link>https://peppe.rs/posts/nixOS/</link>
<pubDate>Tue, 01 Sep 2020 07:08:00 +0000</pubDate>
<guid>https://peppe.rs/posts/nixOS/</guid>
</item>
<item>
<title>Gripes With Go</title>
<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;
&lt;ol type="1"&gt;
&lt;li&gt;&lt;a href="#lack-of-sum-types"&gt;Lack of sum types&lt;/a&gt;&lt;/li&gt;
&lt;li&gt;&lt;a href="#type-assertions"&gt;Type assertions&lt;/a&gt;&lt;/li&gt;
&lt;li&gt;&lt;a href="#date-and-time"&gt;Date and Time&lt;/a&gt;&lt;/li&gt;
&lt;li&gt;&lt;a href="#statements-over-expressions"&gt;Statements over
Expressions&lt;/a&gt;&lt;/li&gt;
&lt;li&gt;&lt;a href="#erroring-out-on-unused-variables"&gt;Erroring out on unused
variables&lt;/a&gt;&lt;/li&gt;
&lt;li&gt;&lt;a href="#error-handling"&gt;Error handling&lt;/a&gt;&lt;/li&gt;
&lt;/ol&gt;
&lt;h3 id="lack-of-sum-types"&gt;Lack of Sum types&lt;/h3&gt;
&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;
&lt;p&gt;A type to represent gender for example:&lt;/p&gt;
&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" tabindex="-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;
&lt;span id="cb1-2"&gt;&lt;a href="#cb1-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb1-3"&gt;&lt;a href="#cb1-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;const&lt;/span&gt; &lt;span class="op"&gt;(&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-4"&gt;&lt;a href="#cb1-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    Male Gender &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="ot"&gt;iota&lt;/span&gt;  &lt;span class="co"&gt;// assigns Male to 0&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-5"&gt;&lt;a href="#cb1-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    Female              &lt;span class="co"&gt;// assigns Female to 1&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-6"&gt;&lt;a href="#cb1-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    Other               &lt;span class="co"&gt;// assigns Other to 2&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-7"&gt;&lt;a href="#cb1-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;)&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-8"&gt;&lt;a href="#cb1-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb1-9"&gt;&lt;a href="#cb1-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;fmt&lt;span class="op"&gt;.&lt;/span&gt;Println&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; Male&lt;span class="op"&gt;)&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-10"&gt;&lt;a href="#cb1-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// My gender is 0&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-11"&gt;&lt;a href="#cb1-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// Oops! We have to implement String() for Gender ...&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-12"&gt;&lt;a href="#cb1-12" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb1-13"&gt;&lt;a href="#cb1-13" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;func&lt;/span&gt; &lt;span class="op"&gt;(&lt;/span&gt;g Gender&lt;span class="op"&gt;)&lt;/span&gt; String&lt;span class="op"&gt;()&lt;/span&gt; &lt;span class="dt"&gt;string&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-14"&gt;&lt;a href="#cb1-14" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="cf"&gt;switch&lt;/span&gt; &lt;span class="op"&gt;(&lt;/span&gt;g&lt;span class="op"&gt;)&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-15"&gt;&lt;a href="#cb1-15" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="cf"&gt;case&lt;/span&gt; &lt;span class="dv"&gt;0&lt;/span&gt;&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="cf"&gt;return&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;Male&amp;quot;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-16"&gt;&lt;a href="#cb1-16" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="cf"&gt;case&lt;/span&gt; &lt;span class="dv"&gt;1&lt;/span&gt;&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="cf"&gt;return&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;Female&amp;quot;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-17"&gt;&lt;a href="#cb1-17" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="cf"&gt;default&lt;/span&gt;&lt;span class="op"&gt;:&lt;/span&gt; &lt;span class="cf"&gt;return&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;Other&amp;quot;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-18"&gt;&lt;a href="#cb1-18" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-19"&gt;&lt;a href="#cb1-19" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-20"&gt;&lt;a href="#cb1-20" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb1-21"&gt;&lt;a href="#cb1-21" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// You can accidentally do stupid stuff like:&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-22"&gt;&lt;a href="#cb1-22" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;gender &lt;span class="op"&gt;:=&lt;/span&gt; Male &lt;span class="op"&gt;+&lt;/span&gt; &lt;span class="dv"&gt;1&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The Haskell equivalent of the same:&lt;/p&gt;
&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" tabindex="-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;
&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;            &lt;span class="op"&gt;|&lt;/span&gt; &lt;span class="dt"&gt;Female&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-3"&gt;&lt;a href="#cb2-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;            &lt;span class="op"&gt;|&lt;/span&gt; &lt;span class="dt"&gt;Other&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-4"&gt;&lt;a href="#cb2-4" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb2-5"&gt;&lt;a href="#cb2-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb2-6"&gt;&lt;a href="#cb2-6" aria-hidden="true" tabindex="-1"&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;
&lt;h3 id="type-assertions"&gt;Type Assertions&lt;/h3&gt;
&lt;p&gt;A downcast with an optional error check? What could go wrong?&lt;/p&gt;
&lt;p&gt;Type assertions in Go allow you to do:&lt;/p&gt;
&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" tabindex="-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="op"&gt;{}&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="dv"&gt;7&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-2"&gt;&lt;a href="#cb3-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;y&lt;span class="op"&gt;,&lt;/span&gt; goodToGo &lt;span class="op"&gt;:=&lt;/span&gt; x&lt;span class="op"&gt;.(&lt;/span&gt;&lt;span class="dt"&gt;int&lt;/span&gt;&lt;span class="op"&gt;)&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-3"&gt;&lt;a href="#cb3-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="cf"&gt;if&lt;/span&gt; goodToGo &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-4"&gt;&lt;a href="#cb3-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    fmt&lt;span class="op"&gt;.&lt;/span&gt;Println&lt;span class="op"&gt;(&lt;/span&gt;y&lt;span class="op"&gt;)&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-5"&gt;&lt;a href="#cb3-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The error check however is optional:&lt;/p&gt;
&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" tabindex="-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="op"&gt;{}&lt;/span&gt; &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="dv"&gt;7&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb4-2"&gt;&lt;a href="#cb4-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;var&lt;/span&gt; y &lt;span class="op"&gt;:=&lt;/span&gt; x&lt;span class="op"&gt;.(&lt;/span&gt;&lt;span class="dt"&gt;float64&lt;/span&gt;&lt;span class="op"&gt;)&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb4-3"&gt;&lt;a href="#cb4-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;fmt&lt;span class="op"&gt;.&lt;/span&gt;Println&lt;span class="op"&gt;(&lt;/span&gt;y&lt;span class="op"&gt;)&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb4-4"&gt;&lt;a href="#cb4-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// results in a runtime error:&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb4-5"&gt;&lt;a href="#cb4-5" aria-hidden="true" tabindex="-1"&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;
&lt;h3 id="date-and-time"&gt;Date and Time&lt;/h3&gt;
&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;
&lt;pre&gt;&lt;code&gt;Mon Jan 2 15:04:05 MST 2006&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Which is the date produced when you write the first seven natural
numbers like so:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;01/02 03:04:05 &amp;#39;06 -0700&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Parsing a string in &lt;code&gt;YYYY-MM-DD&lt;/code&gt; format would look
something like:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;const&lt;/span&gt; layout &lt;span class="op"&gt;=&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;2006-01-02&amp;quot;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb7-2"&gt;&lt;a href="#cb7-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;time&lt;span class="op"&gt;.&lt;/span&gt;Parse&lt;span class="op"&gt;(&lt;/span&gt;layout&lt;span class="op"&gt;,&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;2020-08-01&amp;quot;&lt;/span&gt;&lt;span class="op"&gt;)&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&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;
&lt;h3 id="statements-over-expressions"&gt;Statements over Expressions&lt;/h3&gt;
&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;
&lt;p&gt;Rust allows you to create local namespaces, and treats blocks
(&lt;code&gt;{}&lt;/code&gt;) as expressions:&lt;/p&gt;
&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" tabindex="-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 class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb8-2"&gt;&lt;a href="#cb8-2" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb8-3"&gt;&lt;a href="#cb8-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb8-4"&gt;&lt;a href="#cb8-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    nine &lt;span class="op"&gt;*&lt;/span&gt; three&lt;/span&gt;
&lt;span id="cb8-5"&gt;&lt;a href="#cb8-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;The Go equivalent of the same:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;twenty_seven &lt;span class="op"&gt;:=&lt;/span&gt; &lt;span class="ot"&gt;nil&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb9-2"&gt;&lt;a href="#cb9-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb9-3"&gt;&lt;a href="#cb9-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&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&gt;
&lt;span id="cb9-4"&gt;&lt;a href="#cb9-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;nine &lt;span class="op"&gt;:=&lt;/span&gt; three &lt;span class="op"&gt;*&lt;/span&gt; three&lt;/span&gt;
&lt;span id="cb9-5"&gt;&lt;a href="#cb9-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;twenty_seven &lt;span class="op"&gt;=&lt;/span&gt; nine &lt;span class="op"&gt;*&lt;/span&gt; three&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h3 id="erroring-out-on-unused-variables"&gt;Erroring out on unused
variables&lt;/h3&gt;
&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;
&lt;h3 id="error-handling"&gt;Error handling&lt;/h3&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="cf"&gt;if&lt;/span&gt; err &lt;span class="op"&gt;!=&lt;/span&gt; &lt;span class="ot"&gt;nil&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;
&lt;p&gt;Need I say more? I will, for good measure:&lt;/p&gt;
&lt;ol type="1"&gt;
&lt;li&gt;Error handling is optional&lt;/li&gt;
&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;
&lt;/ol&gt;
&lt;p&gt;I prefer Haskell’s “Monadic” error handling, which is employed by
Rust as well:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// 1. error handling is compulsory&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-2"&gt;&lt;a href="#cb11-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// 2. errors are propagated with the `?` operator&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-3"&gt;&lt;a href="#cb11-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb11-4"&gt;&lt;a href="#cb11-4" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb11-5"&gt;&lt;a href="#cb11-5" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb11-6"&gt;&lt;a href="#cb11-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb11-7"&gt;&lt;a href="#cb11-7" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb11-8"&gt;&lt;a href="#cb11-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb11-9"&gt;&lt;a href="#cb11-9" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb11-10"&gt;&lt;a href="#cb11-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-11"&gt;&lt;a href="#cb11-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb11-12"&gt;&lt;a href="#cb11-12" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb11-13"&gt;&lt;a href="#cb11-13" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="co"&gt;// `contents` is an enum known as Result:&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-14"&gt;&lt;a href="#cb11-14" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb11-15"&gt;&lt;a href="#cb11-15" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="cf"&gt;match&lt;/span&gt; contents &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-16"&gt;&lt;a href="#cb11-16" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb11-17"&gt;&lt;a href="#cb11-17" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb11-18"&gt;&lt;a href="#cb11-18" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb11-19"&gt;&lt;a href="#cb11-19" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h3 id="conclusion"&gt;Conclusion&lt;/h3&gt;
&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>
<link>https://peppe.rs/posts/gripes_with_go/</link>
<pubDate>Sat, 01 Aug 2020 11:55:00 +0000</pubDate>
<guid>https://peppe.rs/posts/gripes_with_go/</guid>
</item>
<item>
<title>Turing Complete Type Systems</title>
<description>&lt;p&gt;Rust’s type system is Turing complete:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;&lt;a href="https://github.com/doctorn/trait-eval/"&gt;FizzBuzz with Rust
Traits&lt;/a&gt;&lt;/li&gt;
&lt;li&gt;&lt;a href="https://github.com/Ashymad/fortraith"&gt;A Forth
implementation with Rust Traits&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;It is impossible to determine if a program written in a generally
Turing complete system will ever stop. That is, it is impossible to
write a program &lt;code&gt;f&lt;/code&gt; that determines if a program
&lt;code&gt;g&lt;/code&gt;, where &lt;code&gt;g&lt;/code&gt; is written in a Turing complete
programming language, will ever halt. The &lt;a
href="https://en.wikipedia.org/wiki/Halting_problem"&gt;Halting Problem&lt;/a&gt;
is in fact, an &lt;a
href="https://en.wikipedia.org/wiki/Undecidable_problem"&gt;undecidable
problem&lt;/a&gt;.&lt;/p&gt;
&lt;p&gt;&lt;em&gt;How is any of this relevant?&lt;/em&gt;&lt;/p&gt;
&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;
&lt;p&gt;I understand that this post lacks content.&lt;/p&gt;</description>
<link>https://peppe.rs/posts/turing_complete_type_systems/</link>
<pubDate>Wed, 17 Jun 2020 18:30:00 +0000</pubDate>
<guid>https://peppe.rs/posts/turing_complete_type_systems/</guid>
</item>
<item>
<title>Auto-currying Rust Functions</title>
<description>&lt;p&gt;This post contains a gentle introduction to procedural macros in Rust
and a guide to writing a procedural macro to curry Rust functions. The
source code for the entire library can be found &lt;a
href="https://github.com/nerdypepper/cutlass"&gt;here&lt;/a&gt;. It is also
available on &lt;a
href="https://crates.io/crates/cutlass"&gt;crates.io&lt;/a&gt;.&lt;/p&gt;
&lt;p&gt;The following links might prove to be useful before getting
started:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;&lt;a
href="https://doc.rust-lang.org/reference/procedural-macros.html"&gt;Procedural
Macros&lt;/a&gt;&lt;/li&gt;
&lt;li&gt;&lt;a href="https://en.wikipedia.org/wiki/Currying"&gt;Currying&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;Or you can pretend you read them, because I have included a primer
here :)&lt;/p&gt;
&lt;h3 id="contents"&gt;Contents&lt;/h3&gt;
&lt;ol type="1"&gt;
&lt;li&gt;&lt;a href="#currying"&gt;Currying&lt;/a&gt;&lt;br /&gt;
&lt;/li&gt;
&lt;li&gt;&lt;a href="#procedural-macros"&gt;Procedural Macros&lt;/a&gt;&lt;br /&gt;
&lt;/li&gt;
&lt;li&gt;&lt;a href="#definitions"&gt;Definitions&lt;/a&gt;&lt;br /&gt;
&lt;/li&gt;
&lt;li&gt;&lt;a href="#refinement"&gt;Refinement&lt;/a&gt;&lt;br /&gt;
&lt;/li&gt;
&lt;li&gt;&lt;a href="#the-in-betweens"&gt;The In-betweens&lt;/a&gt;&lt;br /&gt;
     5.1 &lt;a href="#dependencies"&gt;Dependencies&lt;/a&gt;&lt;br /&gt;
     5.2 &lt;a href="#the-attribute-macro"&gt;The attribute macro&lt;/a&gt;&lt;br /&gt;
     5.3 &lt;a href="#function-body"&gt;Function Body&lt;/a&gt;&lt;br /&gt;
     5.4 &lt;a href="#function-signature"&gt;Function Signature&lt;/a&gt;&lt;br /&gt;
     5.5 &lt;a href="#getting-it-together"&gt;Getting it together&lt;/a&gt;&lt;br /&gt;
&lt;/li&gt;
&lt;li&gt;&lt;a href="#debugging-and-testing"&gt;Debugging and Testing&lt;/a&gt;&lt;br /&gt;
&lt;/li&gt;
&lt;li&gt;&lt;a href="#notes"&gt;Notes&lt;/a&gt;&lt;br /&gt;
&lt;/li&gt;
&lt;li&gt;&lt;a href="#conclusion"&gt;Conclusion&lt;/a&gt;&lt;/li&gt;
&lt;/ol&gt;
&lt;h3 id="currying"&gt;Currying&lt;/h3&gt;
&lt;p&gt;Currying is the process of transformation of a function call like
&lt;code&gt;f(a, b, c)&lt;/code&gt; to &lt;code&gt;f(a)(b)(c)&lt;/code&gt;. A curried function
returns a concrete value only when it receives all its arguments! If it
does recieve an insufficient amount of arguments, say 1 of 3, it returns
a &lt;em&gt;curried function&lt;/em&gt;, that returns after receiving 2
arguments.&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;curry(f(a, b, c)) = h(a)(b)(c)

h(x) = g   &amp;lt;- curried function that takes upto 2 args (g)
g(y) = k   &amp;lt;- curried function that takes upto 1 arg (k)
k(z) = v   &amp;lt;- a value (v)

Keen readers will conclude the following,
h(x)(y)(z) = g(y)(z) = k(z) = v&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Mathematically, if &lt;code&gt;f&lt;/code&gt; is a function that takes two
arguments &lt;code&gt;x&lt;/code&gt; and &lt;code&gt;y&lt;/code&gt;, such that
&lt;code&gt;x ϵ X&lt;/code&gt;, and &lt;code&gt;y ϵ Y&lt;/code&gt; , we write it as:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;f: (X × Y) -&amp;gt; Z&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;where &lt;code&gt;×&lt;/code&gt; denotes the Cartesian product of set
&lt;code&gt;X&lt;/code&gt; and &lt;code&gt;Y&lt;/code&gt;, and curried &lt;code&gt;f&lt;/code&gt; (denoted
by &lt;code&gt;h&lt;/code&gt; here) is written as:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;h: X -&amp;gt; (Y -&amp;gt; Z)&lt;/code&gt;&lt;/pre&gt;
&lt;h3 id="procedural-macros"&gt;Procedural Macros&lt;/h3&gt;
&lt;p&gt;These are functions that take code as input and spit out modified
code as output. Powerful stuff. Rust has three kinds of proc-macros:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;Function like macros&lt;br /&gt;
&lt;/li&gt;
&lt;li&gt;Derive macros: &lt;code&gt;#[derive(...)]&lt;/code&gt;, used to automatically
implement traits for structs/enums&lt;br /&gt;
&lt;/li&gt;
&lt;li&gt;and Attribute macros: &lt;code&gt;#[test]&lt;/code&gt;, usually slapped onto
functions&lt;/li&gt;
&lt;/ul&gt;
&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;
&lt;h3 id="definitions"&gt;Definitions&lt;/h3&gt;
&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;
&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" tabindex="-1"&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;
&lt;span id="cb4-2"&gt;&lt;a href="#cb4-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="cf"&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;
&lt;span id="cb4-3"&gt;&lt;a href="#cb4-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&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;
&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" tabindex="-1"&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;
&lt;span id="cb5-2"&gt;&lt;a href="#cb5-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="cf"&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;
&lt;span id="cb5-3"&gt;&lt;a href="#cb5-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="cf"&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;
&lt;span id="cb5-4"&gt;&lt;a href="#cb5-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;      &lt;span class="cf"&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;
&lt;span id="cb5-5"&gt;&lt;a href="#cb5-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb5-6"&gt;&lt;a href="#cb5-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb5-7"&gt;&lt;a href="#cb5-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;A couple of things to note:&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;Return types&lt;/strong&gt;&lt;br /&gt;
We 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;
&lt;p&gt;If you have been following along, you should be able to tell that the
return type of &lt;code&gt;add_curried1&lt;/code&gt; is:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;impl Fn(u32) -&amp;gt; (impl Fn(u32) -&amp;gt; u32)&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;We can drop the parentheses because &lt;code&gt;-&amp;gt;&lt;/code&gt; is right
associative:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;impl Fn(u32) -&amp;gt; impl Fn(u32) -&amp;gt; u32
&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;&lt;strong&gt;Accessing environment&lt;/strong&gt;&lt;br /&gt;
A 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;
&lt;h3 id="refinement"&gt;Refinement&lt;/h3&gt;
&lt;p&gt;Armed with knowledge, we refine our expected output, this time,
employing closures:&lt;/p&gt;
&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" tabindex="-1"&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;
&lt;span id="cb8-2"&gt;&lt;a href="#cb8-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="cf"&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;span id="cb8-3"&gt;&lt;a href="#cb8-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Alas, that does not compile either! It errors out with the following
message:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;error[E0562]: `impl Trait` not allowed outside of function
and inherent method return types
  --&amp;gt; src/main.rs:17:37
   |
   | fn add(x: u32) -&amp;gt; impl Fn(u32) -&amp;gt; impl Fn(u32) -&amp;gt; u32
   |                                   ^^^^^^^^^^^^^^^^^^^
&lt;/code&gt;&lt;/pre&gt;
&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;
&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;
&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" tabindex="-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;
&lt;span id="cb10-2"&gt;&lt;a href="#cb10-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb10-3"&gt;&lt;a href="#cb10-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb10-4"&gt;&lt;a href="#cb10-4" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb10-5"&gt;&lt;a href="#cb10-5" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb10-6"&gt;&lt;a href="#cb10-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb10-7"&gt;&lt;a href="#cb10-7" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb10-8"&gt;&lt;a href="#cb10-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="cf"&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;span id="cb10-9"&gt;&lt;a href="#cb10-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&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;
&lt;h3 id="the-in-betweens"&gt;The In-Betweens&lt;/h3&gt;
&lt;p&gt;Let us write the magical bits that take us from function to curried
function.&lt;/p&gt;
&lt;p&gt;Initialize your workspace with &lt;code&gt;cargo new --lib currying&lt;/code&gt;.
Proc-macro crates are libraries with exactly one export, the macro
itself. Add a &lt;code&gt;tests&lt;/code&gt; directory to your crate root. Your
directory should look something like this:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;.
├── Cargo.toml
├── src
│   └── lib.rs
└── tests
    └── smoke.rs&lt;/code&gt;&lt;/pre&gt;
&lt;h4 id="dependencies"&gt;Dependencies&lt;/h4&gt;
&lt;p&gt;We will be using a total of 3 external crates:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;&lt;a
href="https://docs.rs/proc-macro2/1.0.12/proc_macro2/"&gt;proc_macro2&lt;/a&gt;&lt;/li&gt;
&lt;li&gt;&lt;a href="https://docs.rs/syn/1.0.18/syn/index.html"&gt;syn&lt;/a&gt;&lt;/li&gt;
&lt;li&gt;&lt;a
href="https://docs.rs/quote/1.0.4/quote/index.html"&gt;quote&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;Here’s a sample &lt;code&gt;Cargo.toml&lt;/code&gt;:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;# Cargo.toml

[dependencies]
proc-macro2 = &amp;quot;1.0.9&amp;quot;
quote = &amp;quot;1.0&amp;quot;

[dependencies.syn]
version = &amp;quot;1.0&amp;quot;
features = [&amp;quot;full&amp;quot;]

[lib]
proc-macro = true  # this is important!&lt;/code&gt;&lt;/pre&gt;
&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;
&lt;h4 id="the-attribute-macro"&gt;The attribute macro&lt;/h4&gt;
&lt;p&gt;Drop this into &lt;code&gt;src/lib.rs&lt;/code&gt;, to get the ball rolling.&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb13-2"&gt;&lt;a href="#cb13-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb13-3"&gt;&lt;a href="#cb13-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb13-4"&gt;&lt;a href="#cb13-4" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb13-5"&gt;&lt;a href="#cb13-5" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb13-6"&gt;&lt;a href="#cb13-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb13-7"&gt;&lt;a href="#cb13-7" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb13-8"&gt;&lt;a href="#cb13-8" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb13-9"&gt;&lt;a href="#cb13-9" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb13-10"&gt;&lt;a href="#cb13-10" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb13-11"&gt;&lt;a href="#cb13-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb13-12"&gt;&lt;a href="#cb13-12" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb13-13"&gt;&lt;a href="#cb13-13" aria-hidden="true" tabindex="-1"&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;
&lt;p&gt;&lt;strong&gt;1. Imports&lt;/strong&gt;&lt;/p&gt;
&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;
&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;
&lt;p&gt;&lt;code&gt;ItemFn&lt;/code&gt; from the &lt;code&gt;syn&lt;/code&gt; crate holds the parsed
&lt;code&gt;TokenStream&lt;/code&gt; of a Rust function.
&lt;code&gt;parse_macro_input!&lt;/code&gt; is a helper macro provided by
&lt;code&gt;syn&lt;/code&gt;.&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;2. The lone export&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;Annotate the only &lt;code&gt;pub&lt;/code&gt; of our crate with
&lt;code&gt;#[proc_macro_attribute]&lt;/code&gt;. This tells rustc that
&lt;code&gt;curry&lt;/code&gt; is a procedural macro, and allows us to use it as
&lt;code&gt;#[crate_name::curry]&lt;/code&gt; in other crates. Note the signature of
the &lt;code&gt;curry&lt;/code&gt; function. &lt;code&gt;_attr&lt;/code&gt; is the
&lt;code&gt;TokenStream&lt;/code&gt; representing the attribute itself,
&lt;code&gt;item&lt;/code&gt; refers to the thing we slapped our macro into, in this
case a function (like &lt;code&gt;add&lt;/code&gt;). The return value is a modified
&lt;code&gt;TokenStream&lt;/code&gt;, this will contain our curried version of
&lt;code&gt;add&lt;/code&gt;.&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;3. The helper macro&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;A &lt;code&gt;TokenStream&lt;/code&gt; is a little hard to work with, which is
why we have the &lt;code&gt;syn&lt;/code&gt; crate, which provides types to
represent Rust tokens. An &lt;code&gt;RArrow&lt;/code&gt; struct to represent the
return arrow on a function and so on. One of those types is
&lt;code&gt;ItemFn&lt;/code&gt;, that represents an entire Rust function. The
&lt;code&gt;parse_macro_input!&lt;/code&gt; automatically puts the input to our
macro into an &lt;code&gt;ItemFn&lt;/code&gt;. What a gentleman!&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;4. Returning &lt;code&gt;TokenStream&lt;/code&gt;s &lt;/strong&gt;&lt;/p&gt;
&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;
&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;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb14-2"&gt;&lt;a href="#cb14-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb14-3"&gt;&lt;a href="#cb14-3" aria-hidden="true" tabindex="-1"&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;span id="cb14-4"&gt;&lt;a href="#cb14-4" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb14-5"&gt;&lt;a href="#cb14-5" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb14-6"&gt;&lt;a href="#cb14-6" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb14-7"&gt;&lt;a href="#cb14-7" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb14-8"&gt;&lt;a href="#cb14-8" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb14-9"&gt;&lt;a href="#cb14-9" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb14-10"&gt;&lt;a href="#cb14-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&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;
&lt;pre&gt;&lt;code&gt;                       .-- syn::Ident (ident)
                      /
                 fn add(x: u32, y: u32) -&amp;gt; u32
  (fn_token)      /     ~~~~~~~,~~~~~~  ~~~~~~
syn::token::Fn --&amp;#39;            /               \       (output)
                             &amp;#39;                 `- syn::ReturnType
             Punctuated&amp;lt;FnArg, Comma&amp;gt; (inputs)&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Enough analysis, lets produce our first bit of Rust code.&lt;/p&gt;
&lt;h4 id="function-body"&gt;Function Body&lt;/h4&gt;
&lt;p&gt;Recall that the body of a curried &lt;code&gt;add&lt;/code&gt; should look like
this:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="cf"&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;
&lt;p&gt;And in general:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="cf"&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;
&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;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb18-2"&gt;&lt;a href="#cb18-2" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb18-3"&gt;&lt;a href="#cb18-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb18-4"&gt;&lt;a href="#cb18-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb18-5"&gt;&lt;a href="#cb18-5" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb18-6"&gt;&lt;a href="#cb18-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="cf"&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;
&lt;span id="cb18-7"&gt;&lt;a href="#cb18-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&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;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb19-2"&gt;&lt;a href="#cb19-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb19-3"&gt;&lt;a href="#cb19-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb19-4"&gt;&lt;a href="#cb19-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="cf"&gt;match&lt;/span&gt; a &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb19-5"&gt;&lt;a href="#cb19-5" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb19-6"&gt;&lt;a href="#cb19-6" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb19-7"&gt;&lt;a href="#cb19-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb19-8"&gt;&lt;a href="#cb19-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&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;
&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;
&lt;p&gt;With that done, we should be able to write the codegen for the
function body:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb20-2"&gt;&lt;a href="#cb20-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb20-3"&gt;&lt;a href="#cb20-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb20-4"&gt;&lt;a href="#cb20-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="pp"&gt;quote!&lt;/span&gt; &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb20-5"&gt;&lt;a href="#cb20-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="cf"&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;
&lt;span id="cb20-6"&gt;&lt;a href="#cb20-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb20-7"&gt;&lt;a href="#cb20-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&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;
&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;
&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;
&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;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb21-2"&gt;&lt;a href="#cb21-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb21-3"&gt;&lt;a href="#cb21-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb21-4"&gt;&lt;a href="#cb21-4" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb21-5"&gt;&lt;a href="#cb21-5" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb21-6"&gt;&lt;a href="#cb21-6" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb21-7"&gt;&lt;a href="#cb21-7" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb21-8"&gt;&lt;a href="#cb21-8" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb21-9"&gt;&lt;a href="#cb21-9" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb21-10"&gt;&lt;a href="#cb21-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb21-11"&gt;&lt;a href="#cb21-11" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb21-12"&gt;&lt;a href="#cb21-12" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb21-13"&gt;&lt;a href="#cb21-13" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb21-14"&gt;&lt;a href="#cb21-14" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb21-15"&gt;&lt;a href="#cb21-15" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb21-16"&gt;&lt;a href="#cb21-16" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb21-17"&gt;&lt;a href="#cb21-17" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb21-18"&gt;&lt;a href="#cb21-18" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;   &lt;span class="cf"&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;
&lt;span id="cb21-19"&gt;&lt;a href="#cb21-19" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Add a little test to &lt;code&gt;tests/&lt;/code&gt;:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// tests/smoke.rs&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb22-2"&gt;&lt;a href="#cb22-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb22-3"&gt;&lt;a href="#cb22-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb22-4"&gt;&lt;a href="#cb22-4" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb22-5"&gt;&lt;a href="#cb22-5" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb22-6"&gt;&lt;a href="#cb22-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb22-7"&gt;&lt;a href="#cb22-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb22-8"&gt;&lt;a href="#cb22-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;test&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb22-9"&gt;&lt;a href="#cb22-9" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb22-10"&gt;&lt;a href="#cb22-10" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb22-11"&gt;&lt;a href="#cb22-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;You should find something like this in the output of
&lt;code&gt;cargo test&lt;/code&gt;:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;return move | y | move | z | { x + y + z }&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Glorious &lt;code&gt;println!&lt;/code&gt; debugging!&lt;/p&gt;
&lt;h4 id="function-signature"&gt;Function signature&lt;/h4&gt;
&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;
&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;
&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" tabindex="-1"&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;
&lt;span id="cb24-2"&gt;&lt;a href="#cb24-2" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb24-3"&gt;&lt;a href="#cb24-3" aria-hidden="true" tabindex="-1"&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;
&lt;p&gt;In general:&lt;/p&gt;
&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" tabindex="-1"&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="cf"&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;
&lt;span id="cb25-2"&gt;&lt;a href="#cb25-2" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb25-3"&gt;&lt;a href="#cb25-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb25-4"&gt;&lt;a href="#cb25-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;.&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb25-5"&gt;&lt;a href="#cb25-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;.&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb25-6"&gt;&lt;a href="#cb25-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;.&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb25-7"&gt;&lt;a href="#cb25-7" aria-hidden="true" tabindex="-1"&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;
&lt;p&gt;To codegen that, we need the types of:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;all our inputs (arguments)&lt;/li&gt;
&lt;li&gt;the output (the return type)&lt;/li&gt;
&lt;/ul&gt;
&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;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb26-2"&gt;&lt;a href="#cb26-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb26-3"&gt;&lt;a href="#cb26-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb26-4"&gt;&lt;a href="#cb26-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb26-5"&gt;&lt;a href="#cb26-5" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb26-6"&gt;&lt;a href="#cb26-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="cf"&gt;match&lt;/span&gt; a &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb26-7"&gt;&lt;a href="#cb26-7" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb26-8"&gt;&lt;a href="#cb26-8" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb26-9"&gt;&lt;a href="#cb26-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb26-10"&gt;&lt;a href="#cb26-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb26-11"&gt;&lt;a href="#cb26-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb26-12"&gt;&lt;a href="#cb26-12" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb26-13"&gt;&lt;a href="#cb26-13" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="cf"&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;
&lt;span id="cb26-14"&gt;&lt;a href="#cb26-14" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb26-15"&gt;&lt;a href="#cb26-15" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&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;
&lt;ol type="1"&gt;
&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;
&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;
&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" tabindex="-1"&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;
&lt;span id="cb27-2"&gt;&lt;a href="#cb27-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// and not&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb27-3"&gt;&lt;a href="#cb27-3" aria-hidden="true" tabindex="-1"&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;
&lt;/ol&gt;
&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;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb28-2"&gt;&lt;a href="#cb28-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb28-3"&gt;&lt;a href="#cb28-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb28-4"&gt;&lt;a href="#cb28-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="cf"&gt;match&lt;/span&gt; a &lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb28-5"&gt;&lt;a href="#cb28-5" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb28-6"&gt;&lt;a href="#cb28-6" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb28-7"&gt;&lt;a href="#cb28-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb28-8"&gt;&lt;a href="#cb28-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&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;
&lt;p&gt;With all our types ready, we can get on with generating type
aliases:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-2"&gt;&lt;a href="#cb29-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb29-3"&gt;&lt;a href="#cb29-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb29-4"&gt;&lt;a href="#cb29-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb29-5"&gt;&lt;a href="#cb29-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="kw"&gt;fn&lt;/span&gt; generate_type_aliases(&lt;/span&gt;
&lt;span id="cb29-6"&gt;&lt;a href="#cb29-6" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb29-7"&gt;&lt;a href="#cb29-7" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb29-8"&gt;&lt;a href="#cb29-8" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb29-9"&gt;&lt;a href="#cb29-9" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb29-10"&gt;&lt;a href="#cb29-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb29-11"&gt;&lt;a href="#cb29-11" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb29-12"&gt;&lt;a href="#cb29-12" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb29-13"&gt;&lt;a href="#cb29-13" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb29-14"&gt;&lt;a href="#cb29-14" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="co"&gt;// 3&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-15"&gt;&lt;a href="#cb29-15" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="cf"&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;
&lt;span id="cb29-16"&gt;&lt;a href="#cb29-16" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb29-17"&gt;&lt;a href="#cb29-17" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb29-18"&gt;&lt;a href="#cb29-18" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb29-19"&gt;&lt;a href="#cb29-19" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb29-20"&gt;&lt;a href="#cb29-20" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb29-21"&gt;&lt;a href="#cb29-21" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="op"&gt;}&lt;/span&gt;)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-22"&gt;&lt;a href="#cb29-22" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-23"&gt;&lt;a href="#cb29-23" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb29-24"&gt;&lt;a href="#cb29-24" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="cf"&gt;return&lt;/span&gt; type_aliases&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb29-25"&gt;&lt;a href="#cb29-25" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;&lt;strong&gt;1. The return value&lt;/strong&gt;&lt;br /&gt;
We 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;
&lt;p&gt;&lt;strong&gt;2. Format identifier?&lt;/strong&gt;&lt;br /&gt;
I’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;
&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" tabindex="-1"&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;
&lt;span id="cb30-2"&gt;&lt;a href="#cb30-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// the others are of the form&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb30-3"&gt;&lt;a href="#cb30-3" aria-hidden="true" tabindex="-1"&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;
&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;
&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;
&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" tabindex="-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;
&lt;span id="cb31-2"&gt;&lt;a href="#cb31-2" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb31-3"&gt;&lt;a href="#cb31-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb31-4"&gt;&lt;a href="#cb31-4" aria-hidden="true" tabindex="-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;
&lt;span id="cb31-5"&gt;&lt;a href="#cb31-5" aria-hidden="true" tabindex="-1"&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;
&lt;p&gt;Here is the same but with macros expanded:&lt;/p&gt;
&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" tabindex="-1"&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;
&lt;span id="cb32-2"&gt;&lt;a href="#cb32-2" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb32-3"&gt;&lt;a href="#cb32-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb32-4"&gt;&lt;a href="#cb32-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb32-5"&gt;&lt;a href="#cb32-5" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb32-6"&gt;&lt;a href="#cb32-6" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb32-7"&gt;&lt;a href="#cb32-7" aria-hidden="true" tabindex="-1"&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;
&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;
&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" tabindex="-1"&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;
&lt;span id="cb33-2"&gt;&lt;a href="#cb33-2" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb33-3"&gt;&lt;a href="#cb33-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb33-4"&gt;&lt;a href="#cb33-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb33-5"&gt;&lt;a href="#cb33-5" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb33-6"&gt;&lt;a href="#cb33-6" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb33-7"&gt;&lt;a href="#cb33-7" aria-hidden="true" tabindex="-1"&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;
&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;
&lt;p&gt;&lt;strong&gt;3. The TokenStream Vector&lt;/strong&gt;&lt;/p&gt;
&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;
&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;
&lt;h4 id="getting-it-together"&gt;Getting it together&lt;/h4&gt;
&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;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// src/lib.rs&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb34-2"&gt;&lt;a href="#cb34-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb34-3"&gt;&lt;a href="#cb34-3" aria-hidden="true" tabindex="-1"&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;span id="cb34-4"&gt;&lt;a href="#cb34-4" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-5"&gt;&lt;a href="#cb34-5" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-6"&gt;&lt;a href="#cb34-6" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-7"&gt;&lt;a href="#cb34-7" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-8"&gt;&lt;a href="#cb34-8" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-9"&gt;&lt;a href="#cb34-9" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-10"&gt;&lt;a href="#cb34-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb34-11"&gt;&lt;a href="#cb34-11" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-12"&gt;&lt;a href="#cb34-12" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-13"&gt;&lt;a href="#cb34-13" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-14"&gt;&lt;a href="#cb34-14" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb34-15"&gt;&lt;a href="#cb34-15" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-16"&gt;&lt;a href="#cb34-16" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-17"&gt;&lt;a href="#cb34-17" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-18"&gt;&lt;a href="#cb34-18" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-19"&gt;&lt;a href="#cb34-19" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-20"&gt;&lt;a href="#cb34-20" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-21"&gt;&lt;a href="#cb34-21" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt;  )&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb34-22"&gt;&lt;a href="#cb34-22" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb34-23"&gt;&lt;a href="#cb34-23" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-24"&gt;&lt;a href="#cb34-24" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb34-25"&gt;&lt;a href="#cb34-25" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt;  &lt;span class="cf"&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;
&lt;span id="cb34-26"&gt;&lt;a href="#cb34-26" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-27"&gt;&lt;a href="#cb34-27" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-28"&gt;&lt;a href="#cb34-28" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb34-29"&gt;&lt;a href="#cb34-29" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt;      &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb34-30"&gt;&lt;a href="#cb34-30" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;+&lt;/span&gt;  &lt;span class="op"&gt;};&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb34-31"&gt;&lt;a href="#cb34-31" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt; &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&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;
&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;
&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;
&lt;h3 id="debugging-and-testing"&gt;Debugging and Testing&lt;/h3&gt;
&lt;p&gt;Install &lt;code&gt;cargo-expand&lt;/code&gt; via:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;cargo install cargo-expand&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;&lt;code&gt;cargo-expand&lt;/code&gt; is a neat little tool that expands your
macro in places where it is used, and lets you view the generated code!
For example:&lt;/p&gt;
&lt;pre class="shell"&gt;&lt;code&gt;# create a bin package hello
$ cargo new hello

# view the expansion of the println! macro
$ cargo expand

#![feature(prelude_import)]
#[prelude_import]
use std::prelude::v1::*;
#[macro_use]
extern crate std;
fn main() {
  {
    ::std::io::_print(::core::fmt::Arguments::new_v1(
        &amp;amp;[&amp;quot;Hello, world!\n&amp;quot;],
        &amp;amp;match () {
            () =&amp;gt; [],
        },
      ));
  };
}&lt;/code&gt;&lt;/pre&gt;
&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;
&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;
&lt;p&gt;Enough of that, lets get testing:&lt;/p&gt;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;// tests/smoke.rs&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb37-2"&gt;&lt;a href="#cb37-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb37-3"&gt;&lt;a href="#cb37-3" aria-hidden="true" tabindex="-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&gt;
&lt;span id="cb37-4"&gt;&lt;a href="#cb37-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb37-5"&gt;&lt;a href="#cb37-5" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb37-6"&gt;&lt;a href="#cb37-6" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb37-7"&gt;&lt;a href="#cb37-7" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb37-8"&gt;&lt;a href="#cb37-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb37-9"&gt;&lt;a href="#cb37-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb37-10"&gt;&lt;a href="#cb37-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="at"&gt;#[&lt;/span&gt;test&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb37-11"&gt;&lt;a href="#cb37-11" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb37-12"&gt;&lt;a href="#cb37-12" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb37-13"&gt;&lt;a href="#cb37-13" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;Run &lt;code&gt;cargo +nightly test&lt;/code&gt;. You should see a pleasing
message:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;running 1 test
test tests::works ... ok&lt;/code&gt;&lt;/pre&gt;
&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;
&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" tabindex="-1"&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;
&lt;span id="cb39-2"&gt;&lt;a href="#cb39-2" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb39-3"&gt;&lt;a href="#cb39-3" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb39-4"&gt;&lt;a href="#cb39-4" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb39-5"&gt;&lt;a href="#cb39-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="cf"&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;
&lt;span id="cb39-6"&gt;&lt;a href="#cb39-6" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb39-7"&gt;&lt;a href="#cb39-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;      &lt;span class="cf"&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;
&lt;span id="cb39-8"&gt;&lt;a href="#cb39-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb39-9"&gt;&lt;a href="#cb39-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="op"&gt;}&lt;/span&gt;)&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb39-10"&gt;&lt;a href="#cb39-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb39-11"&gt;&lt;a href="#cb39-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb39-12"&gt;&lt;a href="#cb39-12" aria-hidden="true" tabindex="-1"&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;
&lt;p&gt;A sight for sore eyes.&lt;/p&gt;
&lt;p&gt;Here is a more complex example that generates ten multiples of the
first ten natural numbers:&lt;/p&gt;
&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" tabindex="-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;
&lt;span id="cb40-2"&gt;&lt;a href="#cb40-2" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb40-3"&gt;&lt;a href="#cb40-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  x &lt;span class="op"&gt;*&lt;/span&gt; y&lt;/span&gt;
&lt;span id="cb40-4"&gt;&lt;a href="#cb40-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb40-5"&gt;&lt;a href="#cb40-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb40-6"&gt;&lt;a href="#cb40-6" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb40-7"&gt;&lt;a href="#cb40-7" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb40-8"&gt;&lt;a href="#cb40-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="cf"&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;
&lt;span id="cb40-9"&gt;&lt;a href="#cb40-9" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb40-10"&gt;&lt;a href="#cb40-10" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;      &lt;span class="op"&gt;.&lt;/span&gt;collect()&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb40-11"&gt;&lt;a href="#cb40-11" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h3 id="notes"&gt;Notes&lt;/h3&gt;
&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;
&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" tabindex="-1"&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;
&lt;span id="cb41-2"&gt;&lt;a href="#cb41-2" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb41-3"&gt;&lt;a href="#cb41-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;{&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb41-4"&gt;&lt;a href="#cb41-4" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb41-5"&gt;&lt;a href="#cb41-5" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb41-6"&gt;&lt;a href="#cb41-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb41-7"&gt;&lt;a href="#cb41-7" aria-hidden="true" tabindex="-1"&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;
&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;
&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;
&lt;h3 id="conclusion"&gt;Conclusion&lt;/h3&gt;
&lt;p&gt;Currying may not seem to be all that useful. Curried functions are
unwieldy in Rust because the standard library is not built around
currying. If you enjoy the possibilities posed by currying, consider
taking a look at Haskell or Scheme.&lt;/p&gt;
&lt;p&gt;My original intention with &lt;a href="https://peppe.rs"&gt;peppe.rs&lt;/a&gt;
was to post condensed articles, a micro blog, but this one turned out
extra long.&lt;/p&gt;
&lt;p&gt;Perhaps I should call it a ‘macro’ blog :)&lt;/p&gt;
&lt;section id="footnotes" class="footnotes footnotes-end-of-document"
role="doc-endnotes"&gt;
&lt;hr /&gt;
&lt;ol&gt;
&lt;li id="fn1"&gt;&lt;p&gt;&lt;a
href="https://doc.rust-lang.org/book/ch13-01-closures.html"&gt;https://doc.rust-lang.org/book/ch13-01-closures.html&lt;/a&gt;&lt;a
href="#fnref1" class="footnote-back" role="doc-backlink"&gt;↩︎&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;
&lt;li id="fn2"&gt;&lt;p&gt;&lt;a href="https://caniuse.rs"&gt;caniuse.rs&lt;/a&gt; contains an
indexed list of features and their status.&lt;a href="#fnref2"
class="footnote-back" role="doc-backlink"&gt;↩︎&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;
&lt;/ol&gt;
&lt;/section&gt;</description>
<link>https://peppe.rs/posts/auto-currying_rust_functions/</link>
<pubDate>Fri, 08 May 2020 18:30:00 +0000</pubDate>
<guid>https://peppe.rs/posts/auto-currying_rust_functions/</guid>
</item>
<item>
<title>Pixel Art In GIMP</title>
<description>&lt;p&gt;I’ve always been an admirer of pixel art, because of it’s simplicity
and it’s resemblance to bitmap font design. Recently, I decided to take
the dive and make some art of my own.&lt;/p&gt;
&lt;p&gt;I used GIMP because I am fairly familiar with it. Aseprite seems to
be the editor of choice for animated pixel art though.&lt;/p&gt;
&lt;h3 id="setting-up-the-canvas"&gt;Setting up the canvas&lt;/h3&gt;
&lt;p&gt;Picking a canvas size is daunting. Too small, and you won’t be able
to fit in enough detail to make a legible piece. Too big and you’ve got
too many pixels to work with!&lt;/p&gt;
&lt;p&gt;I would suggest starting out with anywhere between 100x100 and
200x200. &lt;a href="https://u.peppe.rs/u9.png"&gt;Here’s&lt;/a&gt; a sample
configuration.&lt;/p&gt;
&lt;p&gt;Sometimes I use a 10x10 grid, &lt;code&gt;View &amp;gt; Show Grid&lt;/code&gt; and
&lt;code&gt;Edit &amp;gt; Preferences &amp;gt; Default Grid &amp;gt; Spacing&lt;/code&gt;, but
that can get jarring, so I throw down a couple of guides, drag right or
down from the left or top gutters for vertical and horizontal guides
respectively.&lt;/p&gt;
&lt;h3 id="choosing-a-brush"&gt;Choosing a Brush&lt;/h3&gt;
&lt;p&gt;The most important part of our setup is the brush. Use the Pencil
Tool (&lt;code&gt;n&lt;/code&gt; on the keyboard) for hard edge drawings. Here’s a
small comparison if you don’t know the difference between a hard edge
and a soft edge:&lt;/p&gt;
&lt;figure&gt;
&lt;img src="https://u.peppe.rs/kz.png" alt="Hard edge vs Soft Edge" /&gt;
&lt;figcaption aria-hidden="true"&gt;Hard edge vs Soft Edge&lt;/figcaption&gt;
&lt;/figure&gt;
&lt;p&gt;I turn the size down all the way to 1 (&lt;code&gt;[&lt;/code&gt; on the
keyboard). Set &lt;code&gt;Dynamics&lt;/code&gt; off. &lt;a
href="https://u.peppe.rs/Fs.png"&gt;Here’s&lt;/a&gt; a sample brush
configuration.&lt;/p&gt;
&lt;h3 id="laying-down-the-pixels"&gt;Laying down the pixels!&lt;/h3&gt;
&lt;p&gt;With the boring stuff out of the way, we can start with our piece. I
usually follow a three step process:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;draw a rough outline&lt;/li&gt;
&lt;li&gt;fill in the shadows&lt;/li&gt;
&lt;li&gt;add highlights&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;But this process is better explained with an example: an onigiri. Let
us start off with a 100x100 canvas.&lt;/p&gt;
&lt;h4 id="drawing-the-outline"&gt;Drawing the outline&lt;/h4&gt;
&lt;p&gt;For the most part, our figure will be symmetric. If you are on GIMP
2.10+, you can take advantage of the Symmetry Painting feature. Go ahead
and enable vertical symmetry,
&lt;code&gt;Window &amp;gt; Dockable Dialogs &amp;gt; Symmetry Painting&lt;/code&gt; and
&lt;code&gt;Symmetry Painting &amp;gt; Symmetry &amp;gt; Mirror &amp;gt; Vertical&lt;/code&gt;.&lt;/p&gt;
&lt;p&gt;If you are running an older version of GIMP, draw in the left side,
duplicate the layer, flip it horizontally, and merge it with the
original.&lt;/p&gt;
&lt;p&gt;Your outline might look something like this:&lt;/p&gt;
&lt;p&gt;&lt;img src="https://u.peppe.rs/mn.png" /&gt;&lt;/p&gt;
&lt;p&gt;Go ahead and fill it in with the fill tool (&lt;code&gt;Shift + b&lt;/code&gt; on
the keyboard), add in some seaweed as well, preferably on a different
layer. You can toggle symmetry on and off to save yourself some
time.&lt;/p&gt;
&lt;p&gt;&lt;img src="https://u.peppe.rs/xu.png" /&gt;&lt;/p&gt;
&lt;h4 id="shadows"&gt;Shadows&lt;/h4&gt;
&lt;p&gt;For now, let us focus on the shadows on the object itself, we’ll come
back to the shadows cast by the object on the surface later.&lt;/p&gt;
&lt;p&gt;Shadows on any surface always follow the shape of the surface. A
spherical onigiri would have a circular shadow:&lt;/p&gt;
&lt;p&gt;&lt;img src="https://u.peppe.rs/FU.png" /&gt;&lt;/p&gt;
&lt;p&gt;A couple of noticeable changes:&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;Layers&lt;/strong&gt;: The layer containing the seaweed has been
hidden.&lt;br /&gt;
&lt;strong&gt;Color&lt;/strong&gt;: The color of the shadow is just a slightly
lighter version of the original object (reduce the Value on the HSV
scale).&lt;br /&gt;
&lt;strong&gt;Area&lt;/strong&gt;: The shadow does not go all the way (notice the
bottom edges).&lt;/p&gt;
&lt;p&gt;The shadow does not go all the way because we will be filling in that
area with another, darker shadow! An image might explain better:&lt;/p&gt;
&lt;p&gt;&lt;img src="https://u.peppe.rs/Br.png" /&gt;&lt;/p&gt;
&lt;p&gt;To emulate soft lights, reduce the value by 2 to 3 points every
iteration. Notice how area &lt;code&gt;1&lt;/code&gt; is much larger than area
&lt;code&gt;4&lt;/code&gt;. This is because an onigiri resembles a bottom heavy
oblate spheroid, a sphere that is slightly fatter around the lower
bottom, and areas &lt;code&gt;1&lt;/code&gt; and &lt;code&gt;2&lt;/code&gt; catch more light
than areas &lt;code&gt;3&lt;/code&gt; and &lt;code&gt;4&lt;/code&gt;.&lt;/p&gt;
&lt;p&gt;Do the same with the seaweed. The seaweed, being a smaller, flatter
object, doesn’t cast much of a shadow, so stop with 1 or 2 iterations of
the gradient:&lt;/p&gt;
&lt;p&gt;&lt;img src="https://u.peppe.rs/T3.png" /&gt;&lt;/p&gt;
&lt;p&gt;We’re getting there!&lt;/p&gt;
&lt;h4 id="highlights"&gt;Highlights&lt;/h4&gt;
&lt;p&gt;This step handles the details on the strongly illuminated portions of
the object. Seaweed is a bit glossy, lighten the edges to make it seem
shiny. The rice is not as shiny, but it does form an uneven surface. Add
in some shadows to promote the idea of rice grains. Here is the finished
result:&lt;/p&gt;
&lt;p&gt;&lt;img src="https://u.peppe.rs/VE.png" /&gt;&lt;/p&gt;
&lt;h3 id="finishing-touches"&gt;Finishing Touches&lt;/h3&gt;
&lt;p&gt;Some color correction and &lt;code&gt;a e s t h e t i c&lt;/code&gt; Japanese
text later, our piece is complete!&lt;/p&gt;
&lt;p&gt;&lt;img src="https://u.peppe.rs/cn.png" /&gt;&lt;/p&gt;
&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;
&lt;p&gt;&lt;img src="https://u.peppe.rs/CH.png" /&gt;&lt;/p&gt;</description>
<link>https://peppe.rs/posts/pixel_art_in_GIMP/</link>
<pubDate>Wed, 08 Apr 2020 18:30:00 +0000</pubDate>
<guid>https://peppe.rs/posts/pixel_art_in_GIMP/</guid>
</item>
<item>
<title>Rapid Refactoring With Vim</title>
<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;
&lt;p&gt;Here’s a small sample of what had to be done (note the lines prefixed
with the arrow):&lt;/p&gt;
&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" tabindex="-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;
&lt;span id="cb1-2"&gt;&lt;a href="#cb1-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;/span&gt;
&lt;span id="cb1-3"&gt;&lt;a href="#cb1-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="at"&gt;#[&lt;/span&gt;test&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-4"&gt;&lt;a href="#cb1-4" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb1-5"&gt;&lt;a href="#cb1-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="pp"&gt;assert_eq!&lt;/span&gt;(&lt;/span&gt;
&lt;span id="cb1-6"&gt;&lt;a href="#cb1-6" aria-hidden="true" tabindex="-1"&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 class="op"&gt;,&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-7"&gt;&lt;a href="#cb1-7" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb1-8"&gt;&lt;a href="#cb1-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        )&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-9"&gt;&lt;a href="#cb1-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;p&gt;had to be converted to:&lt;/p&gt;
&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" tabindex="-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;
&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;/span&gt;
&lt;span id="cb2-3"&gt;&lt;a href="#cb2-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="at"&gt;#[&lt;/span&gt;test&lt;span class="at"&gt;]&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-4"&gt;&lt;a href="#cb2-4" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb2-5"&gt;&lt;a href="#cb2-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="pp"&gt;assert_eq!&lt;/span&gt;(&lt;/span&gt;
&lt;span id="cb2-6"&gt;&lt;a href="#cb2-6" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb2-7"&gt;&lt;a href="#cb2-7" aria-hidden="true" tabindex="-1"&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;
&lt;span id="cb2-8"&gt;&lt;a href="#cb2-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;        )&lt;span class="op"&gt;;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-9"&gt;&lt;a href="#cb2-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;  &lt;span class="op"&gt;}&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h3 id="the-arglist"&gt;The arglist&lt;/h3&gt;
&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;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# `grep -l pattern files` lists all the files&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-2"&gt;&lt;a href="#cb3-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;#  matching the pattern&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-3"&gt;&lt;a href="#cb3-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb3-4"&gt;&lt;a href="#cb3-4" aria-hidden="true" tabindex="-1"&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; &lt;span class="at"&gt;-l&lt;/span&gt; &lt;span class="st"&gt;&amp;#39;cfg\(test\)&amp;#39;&lt;/span&gt; ./&lt;span class="pp"&gt;**&lt;/span&gt;/&lt;span class="pp"&gt;*&lt;/span&gt;.rs&lt;span class="va"&gt;)&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-5"&gt;&lt;a href="#cb3-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb3-6"&gt;&lt;a href="#cb3-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# expands to something like:&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb3-7"&gt;&lt;a href="#cb3-7" aria-hidden="true" tabindex="-1"&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;
&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;
&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;
&lt;pre&gt;&lt;code&gt;:argdo s/from_str/from_value/g&lt;/code&gt;&lt;/pre&gt;
&lt;h3 id="the-quickfix-list"&gt;The quickfix list&lt;/h3&gt;
&lt;p&gt;Next up, replacing &lt;code&gt;r#" ... "#&lt;/code&gt; with
&lt;code&gt;json!( ... )&lt;/code&gt;. I couldn’t search and replace that trivially,
so I went with a macro call &lt;a href="#fn2" class="footnote-ref"
id="fnref2" role="doc-noteref"&gt;&lt;sup&gt;2&lt;/sup&gt;&lt;/a&gt; instead, starting with
the cursor on ‘r’, represented by the caret, in my attempt to breakdown
the process:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;BUFFER:    r#&amp;quot; ... &amp;quot;#;
           ^

ACTION:    vllsjson!(

BUFFER     json!( ... &amp;quot;#;
                ^

ACTION:    &amp;lt;esc&amp;gt;$F#

BUFFER:    json!( ... &amp;quot;#;
                       ^

ACTION:    vhs)&amp;lt;esc&amp;gt;

BUFFER:    json!( ... );&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Here’s the recorded &lt;a href="#fn3" class="footnote-ref" id="fnref3"
role="doc-noteref"&gt;&lt;sup&gt;3&lt;/sup&gt;&lt;/a&gt; macro in all its glory:
&lt;code&gt;vllsjson!(&amp;lt;esc&amp;gt;$F#vhs)&amp;lt;esc&amp;gt;&lt;/code&gt;.&lt;/p&gt;
&lt;p&gt;Great! So now we just go ahead, find every occurrence of
&lt;code&gt;r#&lt;/code&gt; and apply the macro right? Unfortunately, there were
more than a few occurrences of raw strings that had to stay raw strings.
Enter, the quickfix list.&lt;/p&gt;
&lt;p&gt;The idea behind the quickfix list is to jump from one position in a
file to another (maybe in a different file), much like how the arglist
lets you jump from one file to another.&lt;/p&gt;
&lt;p&gt;One of the easiest ways to populate this list with a bunch of
positions is to use &lt;code&gt;vimgrep&lt;/code&gt;:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;# basic usage
:vimgrep pattern files

# search for raw strings
:vimgrep &amp;#39;r#&amp;#39; ./**/*.rs&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Like &lt;code&gt;:next&lt;/code&gt; and &lt;code&gt;:prev&lt;/code&gt;, you can navigate the
quickfix list with &lt;code&gt;:cnext&lt;/code&gt; and &lt;code&gt;:cprev&lt;/code&gt;. Every
time you move up or down the list, vim indicates your index:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;(1 of 131): r#&amp;quot;{&amp;quot;set_tweak&amp;quot;: &amp;quot;highlight&amp;quot;}&amp;quot;#;&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;And just like &lt;code&gt;argdo&lt;/code&gt;, you can &lt;code&gt;cdo&lt;/code&gt; to apply
commands to &lt;em&gt;every&lt;/em&gt; match in the quickfix list:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;:cdo norm! @q&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;But, I had to manually pick out matches, and it involved some button
mashing.&lt;/p&gt;
&lt;h3 id="external-filtering"&gt;External Filtering&lt;/h3&gt;
&lt;p&gt;Some code reviews later, I was asked to format all the json inside
the &lt;code&gt;json!&lt;/code&gt; macro. All you have to do is pass a visual
selection through a pretty json printer. Select the range to be
formatted in visual mode, and hit &lt;code&gt;:&lt;/code&gt;, you will notice the
command line displaying what seems to be gibberish:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;:&amp;#39;&amp;lt;,&amp;#39;&amp;gt;&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;&lt;code&gt;'&amp;lt;&lt;/code&gt; and &lt;code&gt;'&amp;gt;&lt;/code&gt; are &lt;em&gt;marks&lt;/em&gt; &lt;a
href="#fn4" class="footnote-ref" id="fnref4"
role="doc-noteref"&gt;&lt;sup&gt;4&lt;/sup&gt;&lt;/a&gt;. More specifically, they are marks
that vim sets automatically every time you make a visual selection,
denoting the start and end of the selection.&lt;/p&gt;
&lt;p&gt;A range is one or more line specifiers separated by a
&lt;code&gt;,&lt;/code&gt;:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;:1,7       lines 1 through 7
:32        just line 32
:.         the current line
:.,$       the current line to the last line
:&amp;#39;a,&amp;#39;b     mark &amp;#39;a&amp;#39; to mark &amp;#39;b&amp;#39;&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Most &lt;code&gt;:&lt;/code&gt; commands can be prefixed by ranges.
&lt;code&gt;:help usr_10.txt&lt;/code&gt; for more on that.&lt;/p&gt;
&lt;p&gt;Alright, lets pass json through &lt;code&gt;python -m json.tool&lt;/code&gt;, a
json formatter that accepts &lt;code&gt;stdin&lt;/code&gt; (note the use of
&lt;code&gt;!&lt;/code&gt; to make use of an external program):&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;:&amp;#39;&amp;lt;,&amp;#39;&amp;gt;!python -m json.tool&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Unfortunately that didn’t quite work for me because the range
included some non-json text as well, a mix of regex and macros helped
fix that. I think you get the drift.&lt;/p&gt;
&lt;p&gt;Another fun filter I use from time to time is &lt;code&gt;:!sort&lt;/code&gt;, to
sort css attributes, or &lt;code&gt;:!uniq&lt;/code&gt; to remove repeated
imports.&lt;/p&gt;
&lt;section id="footnotes" class="footnotes footnotes-end-of-document"
role="doc-endnotes"&gt;
&lt;hr /&gt;
&lt;ol&gt;
&lt;li id="fn1"&gt;&lt;p&gt;https://github.com/tpope/vim-unimpaired It also handles
various other mappings, &lt;code&gt;]q&lt;/code&gt; and &lt;code&gt;[q&lt;/code&gt; to navigate
the quickfix list for example&lt;a href="#fnref1" class="footnote-back"
role="doc-backlink"&gt;↩︎&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;
&lt;li id="fn2"&gt;&lt;p&gt;&lt;code&gt;:help recording&lt;/code&gt;&lt;a href="#fnref2"
class="footnote-back" role="doc-backlink"&gt;↩︎&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;
&lt;li id="fn3"&gt;&lt;p&gt;When I’m recording a macro, I prefer starting out by
storing it in register &lt;code&gt;q&lt;/code&gt;, and then copying it over to
another register if it works as intended. I think of &lt;code&gt;qq&lt;/code&gt; as
‘quick record’.&lt;a href="#fnref3" class="footnote-back"
role="doc-backlink"&gt;↩︎&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;
&lt;li id="fn4"&gt;&lt;p&gt;&lt;code&gt;:help mark-motions&lt;/code&gt;&lt;a href="#fnref4"
class="footnote-back" role="doc-backlink"&gt;↩︎&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;
&lt;/ol&gt;
&lt;/section&gt;</description>
<link>https://peppe.rs/posts/rapid_refactoring_with_vim/</link>
<pubDate>Tue, 31 Mar 2020 18:30:00 +0000</pubDate>
<guid>https://peppe.rs/posts/rapid_refactoring_with_vim/</guid>
</item>
<item>
<title>Font Size Fallacies</title>
<description>&lt;p&gt;I am not an expert with fonts, but I do have some experience &lt;a
href="#fn1" class="footnote-ref" id="fnref1"
role="doc-noteref"&gt;&lt;sup&gt;1&lt;/sup&gt;&lt;/a&gt;, and common sense. This post aims to
debunk some misconceptions about font sizes!&lt;/p&gt;
&lt;p&gt;11 px on your display is &lt;em&gt;probably not&lt;/em&gt; 11 px on my display.
Let’s do some quick math. I have two displays, 1366x768 @ 21” and
another with 1920x1080 @ 13”, call them &lt;code&gt;A&lt;/code&gt; and
&lt;code&gt;B&lt;/code&gt; for now.&lt;/p&gt;
&lt;p&gt;Display &lt;code&gt;A&lt;/code&gt; has 1,049,088 pixels. A pixel is a square, of
side say, &lt;code&gt;s&lt;/code&gt; cm. The total area covered by my 21” display is
about 1,066 cm^2 (41x26). Thus,&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;Display A
Dimensions: 1366x768 @ 21&amp;quot; (41x26 sq. cm)
1,049,088 s^2 = 1066
            s = 0.0318 cm (side of a pixel on Display A)&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Bear with me, as I repeat the number crunching for Display
&lt;code&gt;B&lt;/code&gt;:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;Display B
Dimensions: 1920x1080 @ 13&amp;quot; (29.5x16.5 sq. cm)
2,073,600 s^2 = 486.75
            s = 0.0153 cm (side of a pixel on Display B)&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;The width of a pixel on Display &lt;code&gt;A&lt;/code&gt; is &lt;em&gt;double&lt;/em&gt; the
width of a pixel on Display &lt;code&gt;B&lt;/code&gt;. The area occupied by a pixel
on Display &lt;code&gt;A&lt;/code&gt; is &lt;em&gt;4 times&lt;/em&gt; the area occupied by a
pixel on Display &lt;code&gt;B&lt;/code&gt;.&lt;/p&gt;
&lt;p&gt;&lt;em&gt;The size of a pixel varies from display to display!&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;A 5x11 bitmap font on Display &lt;code&gt;A&lt;/code&gt; would be around 4 mm
tall whereas the same bitmap font on Display &lt;code&gt;B&lt;/code&gt; would be
around 1.9 mm tall. A 11 px tall character on &lt;code&gt;B&lt;/code&gt; is visually
equivalent to a 5 px character on &lt;code&gt;A&lt;/code&gt;. When you view a
screenshot of Display &lt;code&gt;A&lt;/code&gt; on Display &lt;code&gt;B&lt;/code&gt;, the
contents are shrunk down by a factor of 2!&lt;/p&gt;
&lt;p&gt;So screen resolution is not enough, how else do we measure size?
Pixel Density! Keen readers will realize that the 5^th grade math
problem we solved up there showcases pixel density, or, pixels per cm
(PPCM). Usually we deal with pixels per inch (PPI).&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;Note:&lt;/strong&gt; PPI is not to be confused with DPI &lt;a
href="#fn2" class="footnote-ref" id="fnref2"
role="doc-noteref"&gt;&lt;sup&gt;2&lt;/sup&gt;&lt;/a&gt; (dots per inch). DPI is defined for
printers.&lt;/p&gt;
&lt;p&gt;In our example, &lt;code&gt;A&lt;/code&gt; is a 75 ppi display and &lt;code&gt;B&lt;/code&gt;
is around 165 ppi &lt;a href="#fn3" class="footnote-ref" id="fnref3"
role="doc-noteref"&gt;&lt;sup&gt;3&lt;/sup&gt;&lt;/a&gt;. A low ppi display appears to be
‘pixelated’, because the pixels are more prominent, much like Display
&lt;code&gt;A&lt;/code&gt;. A higher ppi usually means you can view larger images
and render crispier fonts. The average desktop display can stuff 100-200
pixels per inch. Smart phones usually fall into the 400-600 ppi
(XXXHDPI) category. The human eye fails to differentiate detail past 300
ppi.&lt;/p&gt;
&lt;p&gt;&lt;em&gt;So … streaming an 8K video on a 60” TV provides the same clarity
as a HD video on a smart phone?&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;Absolutely. Well, clarity is subjective, but the amount of detail you
can discern on mobile displays has always been limited. Salty consumers
of the Xperia 1 &lt;a href="#fn4" class="footnote-ref" id="fnref4"
role="doc-noteref"&gt;&lt;sup&gt;4&lt;/sup&gt;&lt;/a&gt; will say otherwise.&lt;/p&gt;
&lt;p&gt;Maybe I will talk about font rendering in another post, but thats all
for now. Don’t judge a font size by its screenshot.&lt;/p&gt;
&lt;section id="footnotes" class="footnotes footnotes-end-of-document"
role="doc-endnotes"&gt;
&lt;hr /&gt;
&lt;ol&gt;
&lt;li id="fn1"&gt;&lt;p&gt;https://github.com/nerdypepper/scientifica&lt;a
href="#fnref1" class="footnote-back" role="doc-backlink"&gt;↩︎&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;
&lt;li id="fn2"&gt;&lt;p&gt;https://en.wikipedia.org/wiki/Dots_per_inch&lt;a
href="#fnref2" class="footnote-back" role="doc-backlink"&gt;↩︎&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;
&lt;li id="fn3"&gt;&lt;p&gt;https://www.sven.de/dpi/&lt;a href="#fnref3"
class="footnote-back" role="doc-backlink"&gt;↩︎&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;
&lt;li id="fn4"&gt;&lt;p&gt;https://en.wikipedia.org/wiki/Sony_Xperia_1&lt;a
href="#fnref4" class="footnote-back" role="doc-backlink"&gt;↩︎&lt;/a&gt;&lt;/p&gt;&lt;/li&gt;
&lt;/ol&gt;
&lt;/section&gt;</description>
<link>https://peppe.rs/posts/font_size_fallacies/</link>
<pubDate>Mon, 16 Mar 2020 18:30:00 +0000</pubDate>
<guid>https://peppe.rs/posts/font_size_fallacies/</guid>
</item>
<item>
<title>Termux Tandem</title>
<description>&lt;p&gt;I learnt about &lt;code&gt;termux&lt;/code&gt; from a friend on IRC recently. It
looked super gimmicky to me at first, but it eventually proved to be
useful. Here’s what I use it for:&lt;/p&gt;
&lt;h3 id="rsync"&gt;rsync&lt;/h3&gt;
&lt;p&gt;Ever since I degoogled my android device, syncing files between my
phone and my PC has always been a pain. I’m looking at you MTP. But,
with &lt;code&gt;termux&lt;/code&gt; and &lt;code&gt;sshd&lt;/code&gt; all set up, it’s as
simple as:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;$ arp
Address         HWtype  HWad ...
192.168.43.187  ether   d0:0 ...

$ rsync -avz 192.168.43.187:~/frogs ~/pics/frogs&lt;/code&gt;&lt;/pre&gt;
&lt;h3 id="ssh-tmux"&gt;ssh &amp;amp; tmux&lt;/h3&gt;
&lt;p&gt;My phone doubles as a secondary view into my main machine with
&lt;code&gt;ssh&lt;/code&gt; and &lt;code&gt;tmux&lt;/code&gt;. When I am away from my PC (read:
sitting across the room), I check build status and IRC messages by
&lt;code&gt;ssh&lt;/code&gt;ing into a tmux session running the said build or
weechat.&lt;/p&gt;
&lt;h3 id="file-uploads"&gt;file uploads&lt;/h3&gt;
&lt;p&gt;Not being able to access my (ssh-only) file host was crippling. With
a &lt;code&gt;bash&lt;/code&gt; instance on my phone, I just copied over my ssh
keys, and popped in a file upload script (a glorified &lt;code&gt;scp&lt;/code&gt;).
Now I just have to figure out a way to clean up these file names …&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;~/storage/pictures/ $ ls
02muf5g7b2i41.jpg  7alt3cwg77841.jpg  cl4bsrge7id11.png
mtZabXG.jpg        p8d5c584f2841.jpg  vjUxGjq.jpg&lt;/code&gt;&lt;/pre&gt;
&lt;h3 id="cmus"&gt;cmus&lt;/h3&gt;
&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;
&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>
<link>https://peppe.rs/posts/termux_tandem/</link>
<pubDate>Sat, 07 Mar 2020 18:30:00 +0000</pubDate>
<guid>https://peppe.rs/posts/termux_tandem/</guid>
</item>
<item>
<title>Call To ARMs</title>
<description>&lt;p&gt;My 4th semester involves ARM programming. And proprietary tooling
(Keil C). But we don’t do that here.&lt;/p&gt;
&lt;h3 id="building"&gt;Building&lt;/h3&gt;
&lt;p&gt;Assembling and linking ARM binaries on non-ARM architecture devices
is fairly trivial. I went along with the GNU cross bare metal toolchain
binutils, which provides &lt;code&gt;arm-as&lt;/code&gt; and &lt;code&gt;arm-ld&lt;/code&gt;
(among a bunch of other utils that I don’t care about for now).&lt;/p&gt;
&lt;p&gt;Assemble &lt;code&gt;.s&lt;/code&gt; files with:&lt;/p&gt;
&lt;pre class="shell"&gt;&lt;code&gt;arm-none-eabi-as main.s -g -march=armv8.1-a -o main.out&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;The &lt;code&gt;-g&lt;/code&gt; flag generates extra debugging information that
&lt;code&gt;gdb&lt;/code&gt; picks up. The &lt;code&gt;-march&lt;/code&gt; option establishes
target architecture.&lt;/p&gt;
&lt;p&gt;Link &lt;code&gt;.o&lt;/code&gt; files with:&lt;/p&gt;
&lt;pre class="shell"&gt;&lt;code&gt;arm-none-eabi-ld main.out -o main&lt;/code&gt;&lt;/pre&gt;
&lt;h3 id="running-and-debugging"&gt;Running (and Debugging)&lt;/h3&gt;
&lt;p&gt;Things get interesting here. &lt;code&gt;gdb&lt;/code&gt; on your x86 machine
cannot read nor execute binaries compiled for ARM. So, we simulate an
ARM processor using &lt;code&gt;qemu&lt;/code&gt;. Now qemu allows you to run
&lt;code&gt;gdbserver&lt;/code&gt; on startup. Connecting our local &lt;code&gt;gdb&lt;/code&gt;
instance to &lt;code&gt;gdbserver&lt;/code&gt; gives us a view into the program’s
execution. Easy!&lt;/p&gt;
&lt;p&gt;Run &lt;code&gt;qemu&lt;/code&gt;, with &lt;code&gt;gdbserver&lt;/code&gt; on port
&lt;code&gt;1234&lt;/code&gt;, with our ARM binary, &lt;code&gt;main&lt;/code&gt;:&lt;/p&gt;
&lt;pre class="shell"&gt;&lt;code&gt;qemu-arm -singlestep -g 1234 main&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Start up &lt;code&gt;gdb&lt;/code&gt; on your machine, and connect to
&lt;code&gt;qemu&lt;/code&gt;’s &lt;code&gt;gdbserver&lt;/code&gt;:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;(gdb) set architecture armv8-a
(gdb) target remote localhost:1234
(gdb) file main
Reading symbols from main...  # yay!&lt;/code&gt;&lt;/pre&gt;
&lt;h3 id="gdb-enhanced"&gt;GDB Enhanced&lt;/h3&gt;
&lt;p&gt;&lt;code&gt;gdb&lt;/code&gt; is cool, but it’s not nearly as comfortable as well
fleshed out emulators/IDEs like Keil. Watching registers, CPSR and
memory chunks update &lt;em&gt;is&lt;/em&gt; pretty fun.&lt;/p&gt;
&lt;p&gt;I came across &lt;code&gt;gdb&lt;/code&gt;’s TUI mode (hit &lt;code&gt;C-x C-a&lt;/code&gt;
or type &lt;code&gt;tui enable&lt;/code&gt; at the prompt). TUI mode is a godsend.
It highlights the current line of execution, shows you disassembly
outputs, updated registers, active breakpoints and more.&lt;/p&gt;
&lt;p&gt;&lt;em&gt;But&lt;/em&gt;, it is an absolute eyesore.&lt;/p&gt;
&lt;p&gt;Say hello to &lt;a href="https://github.com/hugsy/gef"&gt;GEF&lt;/a&gt;! “GDB
Enhanced Features” teaches our old dog some cool new tricks. Here are
some additions that made my ARM debugging experience loads better:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;Memory watches&lt;/li&gt;
&lt;li&gt;Register watches, with up to 7 levels of deref (overkill, I
agree)&lt;/li&gt;
&lt;li&gt;Stack tracing&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;And it’s pretty! See for yourself:&lt;/p&gt;
&lt;p&gt;&lt;a href="https://u.peppe.rs/wq.png"&gt;&lt;img
src="https://u.peppe.rs/wq.png" /&gt;&lt;/a&gt;&lt;/p&gt;
&lt;h3 id="editing"&gt;Editing&lt;/h3&gt;
&lt;p&gt;Vim, with &lt;code&gt;syntax off&lt;/code&gt; because it dosen’t handle GNU ARM
syntax too well.&lt;/p&gt;</description>
<link>https://peppe.rs/posts/call_to_ARMs/</link>
<pubDate>Fri, 07 Feb 2020 18:30:00 +0000</pubDate>
<guid>https://peppe.rs/posts/call_to_ARMs/</guid>
</item>
<item>
<title>Color Conundrum</title>
<description>&lt;p&gt;This piece aims to highlight (pun intended) some of the reasons
behind my &lt;a href="https://u.peppe.rs/bF.png"&gt;color free&lt;/a&gt; editor
setup.&lt;/p&gt;
&lt;p&gt;Imagine highlighting an entire book because &lt;em&gt;all&lt;/em&gt; of it is
important. That is exactly what (most) syntax highlighting does. It is
difficult for the human eye to filter out noise in rainbow barf. Use
color to draw attention, not diverge it.&lt;/p&gt;
&lt;p&gt;At the same time, a book devoid of color is &lt;em&gt;boring!&lt;/em&gt; What is
the takeaway from this 10 line paragraph? What are the technical terms
used?&lt;/p&gt;
&lt;p&gt;Prose and code are certainly different, but the fickle minded human
eye is the same. The eye constantly looks for a frame of reference, a
focal point. It grows tired when it can’t find one.&lt;/p&gt;
&lt;p&gt;The following comparison does a better job of explaining (none, ample
and over-the-top highlighting, from left to right):&lt;/p&gt;
&lt;p&gt;&lt;a href="https://u.peppe.rs/lt.png"&gt;&lt;img
src="https://u.peppe.rs/lt.png" /&gt;&lt;/a&gt;&lt;/p&gt;
&lt;p&gt;Without highlighting (far left), it is hard to differentiate between
comments and code! The florid color scheme (far right) is no good
either, it contains too many attention grabbers. The center sample is a
healthy balance of both. Function calls and constants stand out, and
repetitive keywords and other noise (&lt;code&gt;let&lt;/code&gt;, &lt;code&gt;as&lt;/code&gt;)
are mildly dimmed out. Comments and non-code text (sign column, status
text) are dimmed further.&lt;/p&gt;
&lt;p&gt;I’ll stop myself before I rant about color contrast and
combinations.&lt;/p&gt;</description>
<link>https://peppe.rs/posts/color_conundrum/</link>
<pubDate>Mon, 30 Dec 2019 18:30:00 +0000</pubDate>
<guid>https://peppe.rs/posts/color_conundrum/</guid>
</item>
<item>
<title>Static Sites With Bash</title>
<description>&lt;p&gt;After going through a bunch of static site generators (&lt;a
href="https://blog.getpelican.com/"&gt;pelican&lt;/a&gt;, &lt;a
href="https://gohugo.io"&gt;hugo&lt;/a&gt;, &lt;a
href="https://github.com/icyphox/vite"&gt;vite&lt;/a&gt;), I decided to roll my
own. If you are more of the ‘show me the code’ kinda guy, &lt;a
href="https://github.com/nerdypepper/site"&gt;here&lt;/a&gt; you go.&lt;/p&gt;
&lt;h3 id="text-formatting"&gt;Text formatting&lt;/h3&gt;
&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;
&lt;h3 id="directory-structure"&gt;Directory structure&lt;/h3&gt;
&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;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="va"&gt;posts&lt;/span&gt;&lt;span class="op"&gt;=&lt;/span&gt;&lt;span class="va"&gt;$(&lt;/span&gt;&lt;span class="fu"&gt;ls&lt;/span&gt; &lt;span class="at"&gt;-t&lt;/span&gt; ./posts&lt;span class="va"&gt;)&lt;/span&gt;     &lt;span class="co"&gt;# chronological order!&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-2"&gt;&lt;a href="#cb1-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="cf"&gt;for&lt;/span&gt; f &lt;span class="kw"&gt;in&lt;/span&gt; &lt;span class="va"&gt;$posts&lt;/span&gt;&lt;span class="kw"&gt;;&lt;/span&gt; &lt;span class="cf"&gt;do&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-3"&gt;&lt;a href="#cb1-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="va"&gt;file&lt;/span&gt;&lt;span class="op"&gt;=&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;./posts/&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;$f&lt;/span&gt;      &lt;span class="co"&gt;# `ls` mangled our file paths&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-4"&gt;&lt;a href="#cb1-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="bu"&gt;echo&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;generating post &lt;/span&gt;&lt;span class="va"&gt;$file&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb1-5"&gt;&lt;a href="#cb1-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb1-6"&gt;&lt;a href="#cb1-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="va"&gt;html&lt;/span&gt;&lt;span class="op"&gt;=&lt;/span&gt;&lt;span class="va"&gt;$(&lt;/span&gt;&lt;span class="ex"&gt;lowdown&lt;/span&gt; &lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;$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;
&lt;span id="cb1-7"&gt;&lt;a href="#cb1-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;    &lt;span class="bu"&gt;echo&lt;/span&gt; &lt;span class="at"&gt;-e&lt;/span&gt; &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;
&lt;span id="cb1-8"&gt;&lt;a href="#cb1-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="cf"&gt;done&lt;/span&gt;&lt;/span&gt;&lt;/code&gt;&lt;/pre&gt;&lt;/div&gt;
&lt;h3 id="assets"&gt;Assets&lt;/h3&gt;
&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;
&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" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# strip file extension&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-2"&gt;&lt;a href="#cb2-2" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="va"&gt;ext&lt;/span&gt;&lt;span class="op"&gt;=&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;span class="va"&gt;${1&lt;/span&gt;&lt;span class="op"&gt;##&lt;/span&gt;&lt;span class="pp"&gt;*&lt;/span&gt;.&lt;span class="va"&gt;}&lt;/span&gt;&lt;span class="st"&gt;&amp;quot;&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-3"&gt;&lt;a href="#cb2-3" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb2-4"&gt;&lt;a href="#cb2-4" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# generate a random file name&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-5"&gt;&lt;a href="#cb2-5" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="va"&gt;id&lt;/span&gt;&lt;span class="op"&gt;=&lt;/span&gt;&lt;span class="va"&gt;$(&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; &lt;span class="at"&gt;-dc&lt;/span&gt; &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="fu"&gt;fold&lt;/span&gt; &lt;span class="at"&gt;-w&lt;/span&gt; 2 &lt;span class="kw"&gt;|&lt;/span&gt; &lt;span class="fu"&gt;head&lt;/span&gt; &lt;span class="at"&gt;-n&lt;/span&gt; 1 &lt;span class="va"&gt;)&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-6"&gt;&lt;a href="#cb2-6" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="va"&gt;id&lt;/span&gt;&lt;span class="op"&gt;=&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;
&lt;span id="cb2-7"&gt;&lt;a href="#cb2-7" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;/span&gt;
&lt;span id="cb2-8"&gt;&lt;a href="#cb2-8" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="co"&gt;# copy to my file host&lt;/span&gt;&lt;/span&gt;
&lt;span id="cb2-9"&gt;&lt;a href="#cb2-9" aria-hidden="true" tabindex="-1"&gt;&lt;/a&gt;&lt;span class="fu"&gt;scp&lt;/span&gt; &lt;span class="at"&gt;-P&lt;/span&gt; 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;
&lt;span id="cb2-10"&gt;&lt;a href="#cb2-10" aria-hidden="true" tabindex="-1"&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;
&lt;h3 id="templating"&gt;Templating&lt;/h3&gt;
&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>
<link>https://peppe.rs/posts/static_sites_with_bash/</link>
<pubDate>Fri, 22 Nov 2019 18:30:00 +0000</pubDate>
<guid>https://peppe.rs/posts/static_sites_with_bash/</guid>
</item>
<item>
<title>My Setup</title>
<description>&lt;p&gt;Decided to do one of these because everyone does one of these.&lt;/p&gt;
&lt;p&gt;&lt;img src="https://u.peppe.rs/Hb.png" /&gt;&lt;/p&gt;
&lt;p&gt;My entire setup is managed with GNU &lt;code&gt;stow&lt;/code&gt;, making it
easier to replicate on fresh installations. You can find my
configuration files on &lt;a
href="https://github.com/nerdypepper"&gt;GitHub&lt;/a&gt;.&lt;/p&gt;
&lt;p&gt;I run Void Linux (glibc) on my &lt;a
href="https://store.hp.com/us/en/mdp/laptops/envy-13"&gt;HP Envy 13”
(2018)&lt;/a&gt;. To keep things simple, I run a raw X session with
&lt;code&gt;2bwm&lt;/code&gt; as my window manager, along with &lt;code&gt;dunst&lt;/code&gt;
(notification daemon) and Sam’s &lt;a
href="https://github.com/sdhand/compton"&gt;&lt;code&gt;compton&lt;/code&gt;&lt;/a&gt;
(compositor) fork.&lt;/p&gt;
&lt;p&gt;I am a fan of GNU tools, so I use &lt;code&gt;bash&lt;/code&gt; as my shell, and
&lt;code&gt;coreutils&lt;/code&gt; to manage files, archives, strings, paths etc. I
edit files with &lt;code&gt;vim&lt;/code&gt;, chat with &lt;code&gt;weechat&lt;/code&gt;, listen
to music with &lt;code&gt;cmus&lt;/code&gt;, monitor processes with
&lt;code&gt;htop&lt;/code&gt;, manage sessions with &lt;code&gt;tmux&lt;/code&gt;, read pdfs in
&lt;code&gt;zathura&lt;/code&gt;. I rarely ever leave the comfort of my terminal
emulator, &lt;code&gt;urxvt&lt;/code&gt;.&lt;/p&gt;
&lt;p&gt;Most of my academic typesetting is done with TeX, and compiled with
&lt;code&gt;xelatex&lt;/code&gt;. Other &lt;em&gt;fun&lt;/em&gt; documents are made with GIMP
:).&lt;/p&gt;</description>
<link>https://peppe.rs/posts/my_setup/</link>
<pubDate>Wed, 06 Nov 2019 18:30:00 +0000</pubDate>
<guid>https://peppe.rs/posts/my_setup/</guid>
</item>
<item>
<title>WPA Woes</title>
<description>&lt;p&gt;I finally got around to installing Void GNU/Linux on my main
computer. Rolling release, non-systemd, need I say more?&lt;/p&gt;
&lt;p&gt;As with all GNU/Linux distributions, wireless networks had me in a
fix. If you can see this post, it means I’ve managed to get online. It
turns out, &lt;code&gt;wpa_supplicant&lt;/code&gt; was detecting the wrong interface
by default (does it ever select the right one?). Let us fix that:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;$ sudo rm -r /var/service/wpa_supplicant
$ sudo killall dhcpcd&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;What is the right interface though?&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;$ iw dev
   ...
   Interface wlp2s0
   ...&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Aha! Let us run &lt;code&gt;wpa_supplicant&lt;/code&gt; on that interface, as a
background process:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;$ sudo wpa_supplicant -B -i wlp2s0 -c /etc/wpa_supplicant/wpa_supplicant.conf
$ sudo dhcpcd -B wlp2s0
$ ping google.com
PING ...&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Yay! Make those changes perpetual by enabling the service:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;------------------------------------------------------
# Add these to /etc/wpa_supplicant/wpa_supplicant.conf
OPTS=&amp;quot;-B&amp;quot;
WPA_INTERFACE=&amp;quot;wlp2s0&amp;quot;
------------------------------------------------------
$ sudo ln -s /etc/sv/wpa_supplicant /var/service/
$ sudo ln -s /etc/sv/dhcpcd /var/service/
$ sudo sv restart wpa_supplicant
$ sudo sv restart dhcpcd&lt;/code&gt;&lt;/pre&gt;</description>
<link>https://peppe.rs/posts/WPA_woes/</link>
<pubDate>Sat, 12 Oct 2019 16:23:00 +0000</pubDate>
<guid>https://peppe.rs/posts/WPA_woes/</guid>
</item>
<item>
<title>Bye Bye BDFs</title>
<description>&lt;p&gt;Glyph Bitmap Distribution Format is no more, as the creators of &lt;a
href="https://pango.org"&gt;Pango&lt;/a&gt;, one of the most widely used text
rendering libraries, &lt;a
href="https://blogs.gnome.org/mclasen/2019/05/25/pango-future-directions/"&gt;announced&lt;/a&gt;
their plans for Pango 1.44.&lt;/p&gt;
&lt;p&gt;Until recently, Pango used FreeType to draw fonts. They will be
moving over to &lt;a href="https://harfbuzz.org"&gt;Harfbuzz&lt;/a&gt;, an evolution
of FreeType.&lt;/p&gt;
&lt;p&gt;&lt;em&gt;Why?&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;In short, FreeType was hard to work with. It required complex logic,
and provided no advantage over Harfbuzz (other than being able to fetch
opentype metrics with ease).&lt;/p&gt;
&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;
&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>
<link>https://peppe.rs/posts/bye_bye_BDFs/</link>
<pubDate>Wed, 07 Aug 2019 17:26:00 +0000</pubDate>
<guid>https://peppe.rs/posts/bye_bye_BDFs/</guid>
</item>
<item>
<title>Onivim Sucks</title>
<description>&lt;p&gt;&lt;a href="https://v2.onivim.io"&gt;Onivim&lt;/a&gt; is a ‘modern modal editor’,
combining fancy interface and language features with vim-style modal
editing. What’s wrong you ask?&lt;/p&gt;
&lt;p&gt;Apart from &lt;a href="https://github.com/onivim/oni2/issues/550"&gt;buggy
syntax highlighting&lt;/a&gt;, &lt;a
href="https://github.com/onivim/oni2/issues/519"&gt;broken scrolling&lt;/a&gt;
and &lt;a
href="https://github.com/onivim/oni2/issues?q=is%3Aissue+label%3A%22daily+editor+blocker%22+is%3Aopen"&gt;others&lt;/a&gt;,
Onivim is &lt;strong&gt;proprietary&lt;/strong&gt; software. It is licensed under a
commercial &lt;a
href="https://github.com/onivim/oni1/blob/master/Outrun-Labs-EULA-v1.1.md"&gt;end
user agreement license&lt;/a&gt;, which prohibits redistribution in both
object code and source code formats.&lt;/p&gt;
&lt;p&gt;Onivim’s core editor logic (bits that belong to vim), have been
separated from the interface, into &lt;a
href="https://github.com/onivim/libvim"&gt;libvim&lt;/a&gt;. libvim is licensed
under MIT, which means, this ‘extension’ of vim is perfectly in
adherence to &lt;a
href="http://vimdoc.sourceforge.net/htmldoc/uganda.html#license"&gt;vim’s
license text&lt;/a&gt;! Outrun Labs are exploiting this loophole (distributing
vim as a library) to commercialize Onivim.&lt;/p&gt;
&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;
&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>
<link>https://peppe.rs/posts/onivim_sucks/</link>
<pubDate>Fri, 02 Aug 2019 16:32:00 +0000</pubDate>
<guid>https://peppe.rs/posts/onivim_sucks/</guid>
</item>
<item>
<title>Bash Harder With Vim</title>
<description>&lt;p&gt;Bash is tricky, don’t let your editor get in your way. Here’s a
couple of neat additions you could make to your &lt;code&gt;vimrc&lt;/code&gt; for a
better shell programming experience.&lt;/p&gt;
&lt;h3 id="man-pages-inside-vim"&gt;Man pages inside vim&lt;/h3&gt;
&lt;p&gt;Source this script to get started:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;runtime ftplugin/man.vim&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Now, you can open manpages inside vim with &lt;code&gt;:Man&lt;/code&gt;! It adds
nicer syntax highlighting and the ability to jump around with
&lt;code&gt;Ctrl-]&lt;/code&gt; and &lt;code&gt;Ctrl-T&lt;/code&gt;.&lt;/p&gt;
&lt;p&gt;By default, the manpage is opened in a horizontal split, I prefer
using a new tab:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;let g:ft_man_open_mode = &amp;#39;tab&amp;#39;&lt;/code&gt;&lt;/pre&gt;
&lt;h3 id="scratchpad-to-test-your-commands"&gt;Scratchpad to test your
commands&lt;/h3&gt;
&lt;p&gt;I often test my &lt;code&gt;sed&lt;/code&gt; substitutions, here is a sample from
the script used to generate this site:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;# a substitution to convert snake_case to Title Case With Spaces
echo &amp;quot;$1&amp;quot; | sed -E -e &amp;quot;s/\..+$//g&amp;quot;  -e &amp;quot;s/_(.)/ \u\1/g&amp;quot; -e &amp;quot;s/^(.)/\u\1/g&amp;quot;&lt;/code&gt;&lt;/pre&gt;
&lt;p&gt;Instead of dropping into a new shell, just test it out directly from
vim!&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;Yank the line into a register:&lt;/li&gt;
&lt;/ul&gt;
&lt;pre&gt;&lt;code&gt;yy&lt;/code&gt;&lt;/pre&gt;
&lt;ul&gt;
&lt;li&gt;Paste it into the command-line window:&lt;/li&gt;
&lt;/ul&gt;
&lt;pre&gt;&lt;code&gt;q:p&lt;/code&gt;&lt;/pre&gt;
&lt;ul&gt;
&lt;li&gt;Make edits as required:&lt;/li&gt;
&lt;/ul&gt;
&lt;pre&gt;&lt;code&gt;syntax off            # previously run commands
edit index.html       # in a buffer!
w | so %
!echo &amp;quot;new_post.md&amp;quot; | sed -E -e &amp;quot;s/\..+$//g&amp;quot;  --snip--
^--- note the use of &amp;#39;!&amp;#39;&lt;/code&gt;&lt;/pre&gt;
&lt;ul&gt;
&lt;li&gt;Hit enter with the cursor on the line containing your command!&lt;/li&gt;
&lt;/ul&gt;
&lt;pre&gt;&lt;code&gt;$ vim
New Post         # output
Press ENTER or type command to continue&lt;/code&gt;&lt;/pre&gt;</description>
<link>https://peppe.rs/posts/bash_harder_with_vim/</link>
<pubDate>Tue, 30 Jul 2019 18:30:00 +0000</pubDate>
<guid>https://peppe.rs/posts/bash_harder_with_vim/</guid>
</item>
<item>
<title>Hold Position!</title>
<description>&lt;p&gt;Often times, when I run a vim command that makes “big” changes to a
file (a macro or a &lt;code&gt;:vimgrep&lt;/code&gt; command) I lose my original
position and feel disoriented.&lt;/p&gt;
&lt;p&gt;&lt;em&gt;Save position with &lt;code&gt;winsaveview()&lt;/code&gt;!&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;The &lt;code&gt;winsaveview()&lt;/code&gt; command returns a
&lt;code&gt;Dictionary&lt;/code&gt; that contains information about the view of the
current window. This includes the cursor line number, cursor coloumn,
the top most line in the window and a couple of other values, none of
which concern us.&lt;/p&gt;
&lt;p&gt;Before running our command (one that jumps around the buffer, a lot),
we save our view, and restore it once its done, with
&lt;code&gt;winrestview&lt;/code&gt;.&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;let view = winsaveview()
s/\s\+$//gc              &amp;quot; find and (confirm) replace trailing blanks
winrestview(view)        &amp;quot; restore our original view!&lt;/code&gt;&lt;/pre&gt;
&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>
<link>https://peppe.rs/posts/hold_position!/</link>
<pubDate>Tue, 30 Jul 2019 14:45:00 +0000</pubDate>
<guid>https://peppe.rs/posts/hold_position!/</guid>
</item>
<item>
<title>Get Better At Yanking And Putting In Vim</title>
<description>&lt;p&gt;a couple of nifty tricks to help you copy-paste better:&lt;/p&gt;
&lt;ol type="1"&gt;
&lt;li&gt;&lt;p&gt;reselecting previously selected text (i use this to fix botched
selections):&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;gv  &amp;quot; :h gv for more
    &amp;quot; you can use `o` in visual mode to go to the `Other` end of the selection
    &amp;quot; use a motion to fix the selection&lt;/code&gt;&lt;/pre&gt;&lt;/li&gt;
&lt;li&gt;&lt;p&gt;reselecting previously yanked text:&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;`[v`]
`[         &amp;quot; marks the beginning of the previously yanked text   :h `[
`]         &amp;quot; marks the end                                       :h `]
 v         &amp;quot; visual select everything in between

nnoremap gb `[v`]    &amp;quot; &amp;quot;a quick map to perform the above&lt;/code&gt;&lt;/pre&gt;&lt;/li&gt;
&lt;li&gt;&lt;p&gt;pasting and indenting text (in one go):&lt;/p&gt;
&lt;pre&gt;&lt;code&gt;]p   &amp;quot; put (p) and adjust indent to current line
]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;
&lt;/ol&gt;</description>
<link>https://peppe.rs/posts/get_better_at_yanking_and_putting_in_vim/</link>
<pubDate>Tue, 30 Jul 2019 08:43:00 +0000</pubDate>
<guid>https://peppe.rs/posts/get_better_at_yanking_and_putting_in_vim/</guid>
</item>


    </channel>
</rss>