[antlr-interest] Lookbehind and other regex features

Monty Zukowski monty at codetransform.com
Wed Jul 14 09:51:06 PDT 2004


\On Jul 14, 2004, at 5:08 AM, Eric Mahurin wrote:

> Is there any way to accomplish lookbehind in the lexer or parser? This
> is the main thing that I don't immediately see how to do in ANTLR that
> I could in Perl's regex's.

You could implement this with your own actions in ANTLR if you wanted 
to.  Override match() to keep a lookbehind buffer.  Then just check 
against that with semantic predicates.

I'm not familiar with lookbehind, can you point to some examples of its 
usefulness?  I believe using lexer states serves a similar purpose for 
lexers.

Monty

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