From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ludovic =?UTF-8?Q?Court=C3=A8s?= <ludo@gnu.org>
Subject: bug#36772: feature request: checked variant of "substitute*"
Date: Thu, 25 Jul 2019 19:40:48 +0200
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References: <E8613602-3151-405B-AC42-20D0A2CAD299@vllmrt.net>
 <87zhl4c1rc.fsf@elephly.net>
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In-Reply-To: <87zhl4c1rc.fsf@elephly.net> (Ricardo Wurmus's message of "Tue,
 23 Jul 2019 15:35:19 +0200")
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To: Ricardo Wurmus <rekado@elephly.net>
Cc: 36772@debbugs.gnu.org, Robert Vollmert <rob@vllmrt.net>

Hi,

Ricardo Wurmus <rekado@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=E2=80=99t have to duplicate the macro for =
that
> and it=E2=80=99s a simple extension to failing on zero matches.
>
> What do you think?

That=E2=80=99d be a useful extension.

Ludo=E2=80=99.