[antlr-interest] A proposal for keywords

[Loring Craymer]

The example fits, although the mechanism does quite not match your
description.  The lexer would return a token for 0 with type INTEGER; the
parser would try to match "0", logically as type LITERAL_0; since the text
matches, the token would be matched as a LITERAL_0 and the type field
changed.

--Loring



> -----Original Message-----
> From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> bounces at antlr.org] On Behalf Of shmuel siegel
> Sent: Tuesday, May 23, 2006 3:50 PM
> To: antlr-interest at antlr.org
> Subject: Re: [antlr-interest] A proposal for keywords
> 
> Loring Craymer wrote:
> >...
> > For option 2, literal types should be bound in the parser:  that is, the
> > lexer binds the generic type to the token (TEXT or NUMBER, for example)
> > and the dynamically looks up the next token in the literals table
> > whenever attempting to match a literal.  That is, "if" would be first
> > typed as TEXT but matched (and retyped) as LITERAL_if when matching an
> > occurrence of "if" in the parser.
> >
> 
> Why are you limiting yourself to this type of situation. Why don't we
> expand the concept. Why not let the lexer return a set of token types
> that match the TEXT. The parser rule would have to resolve the
> ambiguity. The grammar rule would be considered ambiguous if the parser
> would accept two different types that had the same TEXT.
> 
> Let's say that I have a positional parameter in a function call that can
> take on the number zero or an empty string (I actually have such a
> grammar). It would be nice to be able to specify this explicitly
> (without predicates) even though "zero" is also an "integer" and "empty
> string" is also a "string".
> 
> Or is this what you are saying?
> 
> Shmuel
> 
> 
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