GNU bug report logs - #36772
feature request: checked variant of "substitute*"

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Message #14 received at 36772 <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: Ricardo Wurmus <rekado <at> elephly.net>
Cc: 36772 <at> debbugs.gnu.org, Robert Vollmert <rob <at> vllmrt.net>
Subject: Re: bug#36772: feature request: checked variant of "substitute*"
Date: Thu, 25 Jul 2019 19:40:48 +0200

Hi,

Ricardo Wurmus <rekado <at> elephly.net> skribis:

>> I think it would be great to have the following variant of substitute*:
>>
>> (substitute*-once filename (pattern vars) body)
>>
>> which acts like the usual substitute-*, except it also asserts that the
>> substitution applies to exactly one line in the file, causing a build
>> failure otherwise.
>
> I agree that the effect of substitute* should be checked.  I think
> substitute* should fail when one of its clauses failed to match
> anything.
>
> Each clause could also accept an optional argument to make them only
> match one location.  We wouldn’t have to duplicate the macro for that
> and it’s a simple extension to failing on zero matches.
>
> What do you think?

That’d be a useful extension.

Ludo’.

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