Expansion of a macro

Expansion of a macro

[A0]

Hi all,

How can one find out what a macro expands to?
Error reports are useful when it expands to nonsense, but how
to do this in general?

Re: Expansion of a macro

[tomas]

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On Mon, Apr 20, 2015 at 04:33:07PM +0100, A0 wrote:
> Hi all,
> 
> How can one find out what a macro expands to?
> Error reports are useful when it expands to nonsense, but how
> to do this in general?

There's macroexpand, but perhaps it'll expand more than you'd
like.

If your editor is Emacs, I'd recommend geiser[1]: it has an
"expand region" functionality.

HTH
- -- tomás
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Re: Expansion of a macro

[Mark H Weaver]

A0 <cape.wrath@openmailbox.org> writes:
> How can one find out what a macro expands to?

You can use the ,expand REPL command, e.g.:

scheme@(guile-user)> ,expand (do ((n 10 (- n 1))) ((zero? n) n))
$1 = (let loop ((n 10))
  (if (zero? n)
    (begin (if #f #f) n)
    (loop (- n 1))))

      Mark

Re: Expansion of a macro

[Panicz Maciej Godek]

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Or you can (use-modules (system base compile) (srfi srfi-11))

and then

(define* (expand-form e #:key (opts '()))
  (let-values (((exp env) (decompile
                           (compile e #:from 'scheme
                                    #:to 'tree-il
                                    #:env (current-module))
                           #:from 'tree-il
                           #:to 'scheme
                           #:opts opts)))
    exp))

(define-syntax-rule (expand expression)
  (expand-form 'expression))

-- at least in guile 2.0

Sometimes it is also instructive to use the macro stepper shipped with
Racket:
http://docs.racket-lang.org/macro-debugger/index.html?q=

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Re: Expansion of a macro

[tomas]

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On Mon, Apr 20, 2015 at 09:32:48PM -0400, Mark H Weaver wrote:
> A0 <cape.wrath@openmailbox.org> writes:
> > How can one find out what a macro expands to?
> 
> You can use the ,expand REPL command, e.g.:

Not the OP, but... thanks for this one!

- -- t
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Re: Expansion of a macro

[A0]

On 21/04/15 07:22, tomas@tuxteam.de wrote:
> On Mon, Apr 20, 2015 at 09:32:48PM -0400, Mark H Weaver wrote:
>> A0 <cape.wrath@openmailbox.org> writes:
>>> How can one find out what a macro expands to?
> 
>> You can use the ,expand REPL command, e.g.:
> 
> Not the OP, but... thanks for this one!
> 
> -- t
> 

I second!

Thank you all, you truly have Guile ;)