Re: [PATCH] Implement R7RS 'define-values'

[Ludovic Courtès]

Mark H Weaver <address@hidden> skribis:

> This patch implements 'define-values' as a macro, with a similar
> implementation strategy to the one used in the sample definition given
> in the R7RS.  I hope to provide a more efficient implementation on the
> master branch at some point -- one which does not involve any mutation
> -- but for now I'd like to provide at least something so that code that
> uses it will run on the upcoming Guile 2.0.10.

Sorry for the delay; looks good to me.

Indeed it would be great to see in 2.2 if we can avoid walking the list
of values.

> +      ((_ (var0 ... varn) expr)
> +       (and-map identifier? #'(var0 ... varn))
> +       #`(begin
> +           (define dummy
> +             (call-with-values (lambda () expr)
> +               (case-lambda
> +                 ((var0 ... varn)
> +                  (list var0 ... varn))
> +                 (_ (%define-values-arity-error)))))

Looks like this is precisely a case where top-level “hygiene” comes in
handy, no?

Thanks,
Ludo’.