[antlr-interest] Re: ambiguous grammar

[mzukowski at yci.com]

The easiest way to get the tree you want will be to modify your lexer to
remember that you just saw a $ and that you need to produce DOT, not FLOAT.
"Lexer states" is one approach to this (see docs).  Another would be to use
semantic predicates in the lexer.

Monty

-----Original Message-----
From: beeh1973 <hastur4711 at bigfoot.com> [mailto:hastur4711 at bigfoot.com]
Sent: Monday, January 20, 2003 7:23 AM
To: antlr-interest at yahoogroups.com
Subject: [antlr-interest] Re: ambiguous grammar


--- In antlr-interest at yahoogroups.com, Anakreon Mejdi <amejdi at e...> 
wrote:
>   component:
>     DOLLAR^ FLOAT
>     ;
> This should work.
> There is no DOT because in the NUMBER rule if an DIGIT is matched 
the 
> type is made FLOAT and the DOT is consumed.
> For the same reason there is no NUMBER Token.
>
hi,

it works but does not produce the result i need.
this would create the tree
($ .1)
instead i need the tree
($ . 1)

in fact i do not need DOT to be part of the tree. just to display the
difference. ($ 1) would suffice.

.1 is just a float literal
$.1 is a positional notation: "the first element in $"

another reply gave me the hint to check the provided Java and C 
Grammars.
i will check this way.

thanks a lot,
  alphonse


 

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