[antlr-interest] Real simple grammar - newbie help?!

[Michael Matera]

Hi James,

I don't think this grammar is that simple.  This is not a context-free 
grammar:  The meaning of '.' depends on what follows it.  In other words 
when the Lexer looks at the dot in '.NET' you expect a KEYWORD 
production, but when it sees the dot in 'work.' you expect no token. 
This is a problem.  Can you redesign this language?

Cheers
./m

James Crowley wrote:
> hey guys,
> 
> I've got a really simple grammar that I'm trying to get working, but failing
> miserably at the moment. Would really appreciate some pointers on this...
> 
> root : (keyword|ignore)*;
> keyword : KEYWORD;
> ignore : IGNORE;
> 
> KEYWORD : ABBRV|WORD;
> fragment WORD : ALPHA+;
> fragment ALPHA : 'a'..'z'|'A'..'Z';
> fragment ABBRV : WORD?('.'WORD);
> 
> IGNORE : .{ Skip(); };
> 
> With the following test input:
> 
> "some ASP.NET and .NET stuff. that work."
> 
> I'm wanting a tree that is just a list of keyword nodes,
> 
> "some", "ASP.NET", "and", ".NET", "stuff", "that", "work"
> 
> At the moment I get
> 
> "some", "ASP.NET", "and", ".NET", "stuff. that",
> 
> (for some reason "." appears within the last keyword, and it misses "work"
> 
> If I change the ABBRV clause to
> 
> fragment ABBRV : ('.'WORD);
> 
> then that works fine, but I get keyword (asp) and keyword (.net) -
> seperately - but I need them as a single token. Any help you can give would
> be much appreciated.
> 
> Many thanks
> 
> James
> 
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