acc is never assigned to...

D'oh!

implementations/scheme-chicken/joy.scm

@@ -196,13 +196,11 @@
 (define (tokenize str)  ; Let's do the simple trick.
   (string-split (string-replace (string-replace str "]" " ] ") "[" " [ ")))
 
-(define (parse tokens) (parse0 tokens '()))
-
-(define (parse0 tokens acc)
-  (if (null? tokens) acc
+(define (parse tokens)
+  (if (null? tokens) '()
     (receive (term rest_of_tokens)
       (one-token-lookahead (car tokens) (cdr tokens))
-      (cons term (parse0 rest_of_tokens acc)))))
+      (cons term (parse rest_of_tokens)))))
 
 (define (one-token-lookahead token tokens)
   (match token