[antlr-interest] handling a common prefix

[Monty Zukowski]

Lexers can behave very much like parsers, some people put parser 
functionality into lexers for awkward languages like COBOL or FORTRAN.

Also, see my article on parser filters.  
http://www.codetransform.com/filterexample.html  That way uou could 
have a real parser working the token stream, but then package up the 
prefix constructs into a single token.  Not quite what the example 
shows, but I'm sure you can get the general idea from it and figure it 
out.

I'm heading for a long weekend so I won't be able to answer any more 
'til Monday.

Monty


ANTLR & Java Consultant -- http://www.codetransform.com
ANSI C/GCC transformation toolkit -- 
http://www.codetransform.com/gcc.html
Embrace the Decay -- http://www.codetransform.com/EmbraceDecay.html

On Jul 16, 2004, at 6:10 AM, thrutchy wrote:

> I'm parsing verilog 2000 that allows almost every construct to be
> optionally prefixed by something like this:
>
> (* attribute = expression *)
>
> Because it can appear in front of just about any construct and it has
> an indeterminate number of tokens (due to expression), it is causing
> ambiguities all over the place.
>
> I think one possible solution would be to treat this whole thing as a
> token by the lexer.  I don't really like this solution because I will
> eventually have to go parse what's inside.
>
> Is there something else I can do?  I want something in between a token
> and a parser rule - psuedo token, where the rest of the parser treats
> it as a token so that it can easily look ahead and resolve
> ambiguities, but it can still be parsed into it's individual 
> components.
>
> Eric



 
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