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

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Message-ID: <Pine.LNX.4.64.0708201438180.30570@fbirervta.pbzchgretzou.qr>
Date:	Mon, 20 Aug 2007 14:44:47 +0200 (CEST)
From:	Jan Engelhardt <jengelh@...putergmbh.de>
To:	Bodo Eggert <7eggert@....de>
cc:	Andy Whitcroft <apw@...dowen.org>,
	Eugene Teo <eugeneteo@...nel.sg>, linux-kernel@...r.kernel.org,
	auke-jan.h.kok@...el.com
Subject: Re: [PATCH] Make checkpatch rant about trailing ; at the end of "if"
  expr


On Aug 20 2007 13:52, Bodo Eggert wrote:
>> 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).

So what about this then...


$s = shift @ARGV;
$r = qr/a(??{ $r })?b/;
if ($s =~ /^$r$/) {
	print "Yup, that's good\n";
} else {
	print "fail\n";
}


$ perl foo.pl aabbbb
Not so much
$ perl foo.pl aaaabbbb
Yup, that's good
$ perl foo.pl aaaaabbbb
Not so much


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	Jan
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