From: Francis Cianfrocca <garbagecat10@...>
Date: 2006-09-15T11:22:59+09:00
Subject: Re: Regular expression question.

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On 9/14/06, Tom Copeland <tom@infoether.com> wrote:
>
>  I'm not sure if it's impossible to parse out C-style comments using a
> regular expression, but the various JavaCC grammars I've seen all use
> lexical states to do it instead.  Another complication is trigraphs (*),
> although I think those are unrecognized by default in most C
> preprocessors.


A C-style block comment can indeed be recognized by a regex. In fact, that's
how lexical states are generally invoked in scanners generated by tools like
flex. However, a *nested* C-style block comment can not be detected by a
regex. A (theoretical) language supporting such a construct would be a
context-free language, not a regular language.

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