call/cc give error

[jcubic]

This is an example that helped me find an error in BiwaScheme and its call/cc implementation biwascheme/biwascheme#257. Here is the code. You can use it to test your implementation:

(call/cc (lambda (return)
           (let ((n 5)
                 (result (list))
                 (k #f))
             (set! result (append result (list (call/cc (lambda (return)
                                                          (set! k return)
                                                          "Hello")))))
             (when #t
               (if (zero? n)
                   (return result))
               (set! n (- n 1))
               (k (string-append "Hello <" (number->string n) ">"))))))

It should return:

("Hello <0>")

All elements are implemented but git weird:

<error args 4>

[PollRobots]

Thanks for reporting this!

There's (apparantly) a bug in number->string, if I change your code to

(call/cc (lambda (return)
           (let ((n 5)
                 (result (list))
                 (k #f))
             (set! result (append result (list (call/cc (lambda (return)
                                                          (set! k return)
                                                          "Hello")))))
             (when #t
               (if (zero? n)
                   (return result))
               (set! n (- n 1))
               (k (string-append "Hello <" (number->string n 10) ">"))))))

Then it works as expected

[jcubic]

Nice, awesome project. You should also try to test quasiquote and syntax-rules, check the links, it took a while to create those tests.

[jcubic]

If you want to run the code from unit tests without Ava and by helper code, you will need to write mocks for Ava testing framework, I think that you only need those:

• to.throw macro
• test function that executes the second argument, and can print the message before execution.
• t.is macro the check for equality and print the expression when not equal. With ava in my Scheme, it's a JavaScript method on t object.