implement let loop.

scm.mes

@@ -62,10 +62,19 @@
         (#t (split-values (cdr bindings)
                           (append values (cdar bindings) '())))))
 
-(define-macro (let bindings . body)
-  `((lambda ,(split-params bindings '()) ,@body)
+(define-macro (simple-let bindings rest)
+  `((lambda ,(split-params bindings '()) ,@rest)
     ,@(split-values bindings '())))
 
+(define-macro (let-loop label bindings rest)
+  `(let ((,label (lambda ,(split-params bindings '()) ,@rest)))
+     (,label ,@(split-values bindings '()))))
+
+(define-macro (let bindings-or-label . rest)
+  `(if ,(symbol? bindings-or-label)
+       (let-loop ,bindings-or-label ,(car rest) ,(cdr rest))
+       (simple-let ,bindings-or-label ,rest)))
+
 (define (expand-let* bindings body)
   (cond ((null? bindings)
          `((lambda () ,@body)))

test.mes

@@ -81,6 +81,17 @@
 (display 'let-dun)
 (newline)
 
+(let loop ((lst '(3 2 1)))
+  (display "loop")
+  (newline)
+  (if (null? lst) (begin (display "dun") 'dun)
+      (begin
+        (display "looping: ")
+        (display (car lst))
+        (newline)
+        (loop (cdr lst)))))
+(newline)
+
 (define c 'b)
 `(aa bb ,c)
 (display `(pp qq ,c))