From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ricardo Wurmus <rekado@elephly.net>
Subject: bug#36772: feature request: checked variant of "substitute*"
Date: Tue, 23 Jul 2019 15:35:19 +0200
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References: <E8613602-3151-405B-AC42-20D0A2CAD299@vllmrt.net>
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To: Robert Vollmert <rob@vllmrt.net>
Cc: 36772@debbugs.gnu.org


Hi Robert,

> 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 th=
at
and it=E2=80=99s a simple extension to failing on zero matches.

What do you think?

--
Ricardo