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Re: [PATCH] Implement R7RS 'define-values'
From: |
Ludovic Courtès |
Subject: |
Re: [PATCH] Implement R7RS 'define-values' |
Date: |
Fri, 07 Feb 2014 00:37:28 +0100 |
User-agent: |
Gnus/5.130007 (Ma Gnus v0.7) Emacs/24.3 (gnu/linux) |
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’.
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