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Re: when and unless

From: Ludovic Courtès
Subject: Re: when and unless
Date: Fri, 01 Jul 2011 14:47:54 +0200
User-agent: Gnus/5.110017 (No Gnus v0.17) Emacs/24.0.50 (gnu/linux)

Andy Wingo <address@hidden> skribis:

> One place you might want to use them though is in type checks for Scheme
> code.  We currently don't do very much of that, but probably should in
> the future.  As in:
>   (define (parameter-fluid p)
>     (unless (parameter? p) (wrong-type-arg p 'parameter))
>     (struct-ref p 1))
> The advantage of `unless' over `if' is that the wrong-type-arg is not
> called in tail position, so the error message sees `parameter-fluid' on
> the stack.

Oh, interesting, good point!


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