Re: How can I step through this code?

[Ludovic Courtès]

Hi,

jgart <jgart@dismail.de> skribis:

> How can I step through this code?
>
> (define-syntax do
>   (syntax-rules ()
>     ((do ((var init step ...) ...)
>          (test expr ...)
>          command ...)
>      (letrec
>        ((loop
>          (lambda (var ...)
>            (if test
>                (begin
>                  (if #f #f)
>                  expr ...)
>                (begin
>                  command
>                  ...
>                  (loop (do "step" var step ...)
>                        ...))))))
>        (loop init ...)))
>     ((do "step" x)
>      x)
>     ((do "step" x y)
>      y)))

You can’t: this is a macro and Guile doesn’t have a “macro stepper”
(Racket does).

What you can do though, is define the macro and expand it on examples of
your choosing to see how it behaves:

--8<---------------cut here---------------start------------->8---
scheme@(guile-user)> ,expand (do ((x 0 (+ 1 x))) ((>= x 10)) (pk x))
$7 = (let loop ((x 0))
  (if (>= x 10)
    (if #f #f)
    (begin (pk x) (loop (+ 1 x)))))
scheme@(guile-user)> ,optimize (do ((x 0 (+ 1 x))) ((>= x 10)) (pk x))
$8 = (begin
  (pk 0)
  (pk 1)
  (pk 2)
  (pk 3)
  (pk 4)
  (pk 5)
  (pk 6)
  (pk 7)
  (pk 8)
  (pk 9)
  (if #f #f))
--8<---------------cut here---------------end--------------->8---

(Personally I’ve never used ‘do’ and I don’t feel like starting today. :-))

Ludo’.