add day 15, 16 of devlog

1 files changed, 37 insertions, 0 deletions

diff --git a/posts/SDL2_devlog.md b/posts/SDL2_devlog.md
index 4605b91..72aedef 100644
--- a/posts/SDL2_devlog.md
+++ b/posts/SDL2_devlog.md
@@ -5,6 +5,43 @@ on the editor. The days are listed in reverse chronological
 order, begin from the bottom, if this is your first time on
 this page.
 
+### Day 16
+
+The embedded lisp is coming along nicely, users can load
+a custom `rc.lisp`, which is evaluated on startup. To
+disable to grid on start, for example:
+
+```scheme
+;;; rc.lisp
+(toggle-grid)
+```
+
+Some aliases to switch between brushes:
+
+```scheme
+;;; rc.lisp
+(define (brush kind)
+  (cond
+    ((eq? kind 'f) (brush-fill))
+    ((eq? kind 'c) (brush-circle))
+    ((eq? kind 'l) (brush-line))
+    ((eq? kind 'l+) (brush-line-extend))
+    (else (brush-circle))))
+```
+
+### Day 15
+
+I began writing a standard library for the lisp, in lisp. It
+includes basic list operations: `car`, `cdr`, `null?`,
+`list`, higher order functions: `map`, `filter`, `fold`:
+
+```lisp
+(define (member? item ls)
+  (fold #f
+        (lambda (acc x) (or acc (eq? item x)))
+        ls))
+```
+
 ### Day 14
 
 I attempted a [small art