Re: [Chicken-users] macro systems and chicken (long)

[Alaric Snell-Pym]

On 17 Apr 2008, at 12:58 pm, Alex Shinn wrote:
>   (define-syntax let
>     (er-macro-transformer
>       (lambda (expr rename compare)
>         `((lambda ,(map car (cadr expr)) ,@(cddr expr))
>           ,@(map cadr (cadr expr))))))
>
> or equivalently with MATCH destructuring
>
>   (define-syntax let
>     (er-macro-transformer
>       (lambda (expr rename compare)
>         (match expr
>          ((let ((var val) ...) body ...)
>           `((lambda ,var ,@body)
>             ,@val))))))
>
> could fail if the (var val) ... list were passed as a syntax
> object.  Though probably this would never happen in
> practice.

When *will* it happen in practice? I did have the strong impression
that the input to a transformer would always be a normal s-expr. I
know that what make-syntactic-closure or the renaming function return
might be more exotic objects, but I didn't think the input s-expr
could be.

> Anyway, regarding DEFINE-RECORD, I've personally been doing
> prototyping in Chicken using that and then automatically
> converting to DEFINE-RECORD-TYPE, simply for portability
> among other Schemes.  You can run the following elisp
> function inside the DEFINE-RECORD form to perform the
> expansion.

Can we not write a define-record as a macro on top of define-record-
type? I've not used define-record-type much (it seems a bit
overcomplex) so I'm not sure if there's some fundamental
incompatability...

ABS

--
Alaric Snell-Pym
Work: http://www.snell-systems.co.uk/
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