changed to be tail-recursive

top.rkt

@@ -15,25 +15,26 @@
 ;; @foo['shape: "square" 'color: "red"]{hello}
 (define-syntax-rule (top~ . id)
   (λ x 
-    (define attrs null)
+    (define reversed-pieces ; list of attribute pairs, and last element holds a list of everything else, then reversed
-    (define elements 
+      (reverse (let chomp ([x x])
-      (let chomp ([x x])
         (define result+regexp (and ((length x) . >= . 2) 
-                                         (symbol? (car x)) 
+                                   (symbol? (car x)) 
-                                         ;; accept strings only
+                                   ;; accept strings only
-                                         ;; numbers are difficult because they don't parse as cleanly.
+                                   ;; numbers are difficult because they don't parse as cleanly.
-                                         ;; string will read as a string even if there's no space to the left.
+                                   ;; string will read as a string even if there's no space to the left.
-                                         (or (string? (cadr x))) 
+                                   (or (string? (cadr x))) 
-                                         ;; Looking for symbol ending with a colon
+                                   ;; Looking for symbol ending with a colon
-                                         (regexp-match #rx"^(.*?):(.*)$" (symbol->string (car x)))))
+                                   (regexp-match #rx"^(.*?):$" (symbol->string (car x)))))
         (if result+regexp
-            (begin
+            ; reuse result value. cadr is first group in match. 
-               ; reuse result value cadr is first group in match. 
+            (cons (list (string->symbol (cadr result+regexp))(cadr x)) (chomp (cddr x)))
-              (set! attrs (cons (list (string->symbol (cadr result+regexp))(cadr x)) attrs))
+            (list x)))))
-              (chomp (cddr x)))
-            x)))
     
-    `(id ,@(if (equal? attrs null) null (list (reverse attrs))) ,@elements)))
+    (define-values (body attrs) (if (equal? null reversed-pieces)
+                                    (values null null)
+                                    (values (car reversed-pieces) (cdr reversed-pieces))))
+    
+    `(id ,@(if (equal? attrs null) null (list (reverse attrs))) ,@body)))
 
 
 (define-syntax (bound/c stx)