[antlr-interest] Re: ambiguous grammar

[cintyram <cintyram at yahoo.com>]

hi , i have included a small part from one of my previous grammars.
i followed the suggestions i got on this list and did not have a
seperate token type for '.' DOT but tried to match it where ever
required ;

also for your $.1 rule you might try 
rule : DOLLAR FLOATING ;

with k set appropriately , because now FLOATING is the expected token
for two rules.

please tell if this does not work ;

--- excerpt ---

protected  ALPHA : ('a'..'z' | 'A'..'Z'|'_')  ;
protected DIGIT : '0'..'9'   	;
ID
options {
	testLiterals = true;
}
	:	ALPHA (ALPHA|DIGIT)*	;

protected SUFFIX      :   ('k'|'M')   ; /// kilo mega etc. 
protected EXPONENT :   ( ('e')('+'|'-')?(DIGIT)+ )   ;
protected INT            :	(DIGIT) +    ;  /// match the integral part
 123
protected FLOATING  :   ( '.'  (DIGIT)+ ) ;
NUM   : INT ( FLOATING  ) ? ( SUFFIX )? (EXPONENT ) ? 
            | ( FLOATING  )  ( SUFFIX )? (EXPONENT ) ? 

--- end ---
cheers
ram



--- In antlr-interest at yahoogroups.com, "beeh1973 <hastur4711 at b...>"
<hastur4711 at b...> wrote:
> hi,
> 
> in my language i have float literals like .1 and
> expressions like $.1
> 
> i am using the following lexer rule to recognize numbers
> 
> NUMBER
>  : '.'        { _ttype = DOT; }            // a single dot
>    (((DIGIT)+ { _ttype = FLOAT} )          // a float number
>    ((EXPONENT))?)?
>  |
>    // some more cases for integers and floats > 1
>   ...
> 
> DOLLAR : '$' ;
> 
> 
> in the parser i try to match $.1 with this rule:
> 
> component:
>   DOLLAR^ DOT NUMBER
>   ;
> 
> while parsing $.1 i get an error that FLOAT is unexpected at that 
> point.
> 
> while i understand why this is happening; a call to nextToken simply
> returns the next token which is a FLOAT no DOT, i do not understand 
> how to
> fix the grammar. can anybody help me with this?
> 
> thanks in advance,
>         alphonse bendt


 

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