Re: [PATCH] Make checkpatch rant about trailing ; at the end of "if" expr

From: Bodo Eggert
Date: Mon Aug 20 2007 - 07:53:17 EST


Jan Engelhardt <jengelh@xxxxxxxxxxxxxxx> wrote:
> On Aug 16 2007 10:21, Andy Whitcroft wrote:

>>> + if ($line =~ /\bif\s*\([^\)]*\)\s*\;/) {
>>
>>Heh, you are the second person to suggest this check today, do I detect
>>some ripped out hair due to one of these!
>>
>>I've taken this idea and expanded it to cover if, for and while which
>>can all suffer from this. Using the relative indent to work out which
>>are valid combinations:
>
> But. The above regex does not seem to handle
>
> if ((a = b));
> oops;
>
> I have tried to come up with a superduper regex that handles multiple
> (), but my regex fu seems to stop above two pairs of ().

This is because you can't do that using finite regular expressions.

Regular expressions are Type-3 grammars, but you'd need a Type-2
grammar to express the Dyck language (and you need to parse a Dyck
Language, ignoring the non-dyck-parts).
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