Re: Need help to understand a macro

[Josef Wolf <jw@raven.inka.de>]

On Sat, Mar 20, 2010 at 03:13:45PM +0100, szgyg wrote:
> Josef Wolf wrote:
> >I am trying to understand the defstruct macro from the "teach yourself
> >scheme in fixnum days" tutorial, which can be found in chapter 9 at
> >http://www.ccs.neu.edu/home/dorai/t-y-scheme/t-y-scheme-Z-H-11.html#node_chap_9
> >
> >My first question is of a more generic type. For a better understanding
> >how macros work, I'd like to have a way to show what expansion a macro
> >would generate when it would be used. E.g., I'd like to do something
> >like
> >
> >  (show-expansion (defstruct tree height girth age leaf-shape leaf-color))
> >
> >and get what the expansion of this macro would produce:
> >
> >  (begin
> >    (define make-tree
> >      (lambda fvfv
> >        [ ... and so on ... ]
> 
> Use the trick from the inexplicable JRM's Syntax-rules Primer for
> the Merely Eccentric[1], wrap the output with quote:
> 
> ...
> (let ((ff (map (lambda (f) (if (pair? f) (car f) f))
>                ff)))
>   `'(begin
> ;  ^
>       (define ,(string->symbol
>                 (string-append "make-" s-s))
> ...

Ah, sounds reasonable. Thanks!

> [1]
> http://www.xs4all.nl/~hipster/lib/scheme/gauche/define-syntax-primer.txt

I will save this link for later, since this stuff is still too advanced for
me. In the meantime, I'll be looking for something that's more entry-level...