changed the implementation to call/cc

main.rkt

@@ -55,6 +55,31 @@
 (define a-true? (a-eq? #t))
 (define a-false? (a-eq? #f))
 
+
+(define-syntax assert-expr
+  (syntax-rules ()
+    ((_ fail (expr cond retval))
+     (let ((a expr)) (if (cond a) a (fail retval))))
+    ((_ fail (expr)) expr)
+    )
+  )
+
+(define-syntax let/assert
+  (syntax-rules ()
+    ((_ fail ((v rest ...) ...) b1 ...)
+     (call/cc
+      (λ (fail)
+        (let* ((v (assert-expr fail (rest ...)))
+               ...)
+          b1
+          ...)
+        )
+      )
+     )
+    )
+  )
+
+#|
 (struct exn:let/assert exn (value) #:transparent)
 
 (define (raise-let/assert v)
@@ -85,3 +110,4 @@
      )
     )
   )
+|#