add chars to prelude

prelude.ld

@@ -386,6 +386,19 @@ fn downcase {
 	(str as :string) -> base :downcase (str)
 }
 
+fn chars {
+	"Takes a string and returns its characters as a list. Works only for strings with only ascii characters. Panics on any non-ascii characters."
+	(str as :string) -> match base :chars (str) {
+		(:ok, chrs) -> chrs
+		(:err, msg) -> panic! msg
+	}
+}
+
+fn chars/safe {
+	"Takes a string and returns its characters as a list, wrapped in a result tuple. Works only for strings with only ascii characters. Returns an error tuple on any non-ascii characters."
+	(str as :string) -> base :chars (str)
+}
+
 fn ws? {
 	"Tells if a string is a whitespace character."
 	(" ") -> true
@@ -1386,6 +1399,7 @@ pkg Prelude {
 	box? & boxes
 	butlast & lists strings tuples
 	ceil & math
+	chars & strings
 	clear! & turtles
 	coll? & dicts lists sets tuples
 	colors & turtles

src/base.janet

@@ -235,6 +235,19 @@
 (defn mod [x y] 
   (% x y))
 
+(defn- byte->ascii [c i]
+  (if (< c 128) 
+    (string/from-bytes c)
+    (error (string "non-ASCII character at index" i))))
+
+(defn chars [str]
+  (def out @[])
+  (try 
+    (for i 0 (length str)
+      (array/push out (byte->ascii (str i) i)))
+    ([e] (break [:err e])))
+  [:ok out])
+
 (def ctx {
   "add" +
   "and" ludus/and
@@ -243,6 +256,7 @@
   "atan_2" math/atan2
   "bool" bool
   "ceil" math/ceil
+  "chars" chars
   "concat" concat
   "conj!" conj!
   "conj" conj
@@ -298,10 +312,9 @@
   "upcase" string/ascii-upper
 })
 
-(def base (let [b @{}]
+(def base (let [b @{:^type :dict}]
   (each [k v] (pairs ctx)
     (set (b (keyword k)) v))
   b))
 
-(set (base :^type) :dict)