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Re: when and unless


From: Andy Wingo
Subject: Re: when and unless
Date: Mon, 05 Dec 2011 21:23:15 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/23.3 (gnu/linux)

Heya Ludo,

On Thu 30 Jun 2011 12:44, Andy Wingo <address@hidden> writes:

> I think we should add `when' and `unless' to the default environment.
>
> They go like this:
>
>   (define-syntax when
>     (syntax-rules ()
>       ((_ test then then* ...)
>        (if test (begin then then* ... (if #f #f))))))
>
>   (define-syntax unless
>     (syntax-rules ()
>       ((_ test else else* ...)
>        (if (not test) (begin else else* ... (if #f #f))))))

WDYT?  `unless' is nice for assertions, `when' is its converse, and most
Schemes have them.  I would like to add them to Guile too.

Andy
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