Fixes #304

Add chr macro.

CHANGELOG.md

@@ -2,6 +2,7 @@
 All notable changes to this project will be documented in this file.
 
 ## Unreleased
+- Add `chr` macro.
 - Allow `_` in the `match` macro to match anything without creating a binding
   or doing unification.
 - Add `:range-to` and `:down-to` verbs in the `loop` macro.

src/boot/boot.janet

@@ -316,6 +316,13 @@
          ,payload
          (propagate ,res ,fib)))))
 
+(defmacro chr
+  "Convert a string of length 1 to its byte (ascii) value at compile time."
+  [c]
+  (unless (and (string? c) (= (length c) 1))
+    (error (string/format "expected string of length 1, got %v" c)))
+  (c 0))
+
 (defmacro label
   "Set a label point that is lexically scoped. Name should be a symbol
   that will be bound to the label."

test/suite8.janet

@@ -136,4 +136,7 @@
 (assert (deep= @"cde" (buffer/blit @"" a -1 2 5)) "buffer/blit 4")
 (assert (deep= @"de" (buffer/blit @"" a -1 3 5)) "buffer/blit 5")
 
+# chr
+(assert (= (chr "a") 97) "chr 1")
+
 (end-suite)