[antlr-interest] lexical nondeterminism Problem

[andreaszielke21]

Hi *,

I'm trying to build a lexer that is able to differentiate between 
numbers and dates.
I'm not proficient using antlr-style regular expressions so I'll give 
you a short description of the two tokens.
The lexer should return a date token for anything that matches 
dd?.mm?.yyyy i.e. 1.1.1900 or 05.12.2004.
The lexer should return a number token for anything that matches
x+(,x+)? i.e. 3,14 or 42.

My input file for antlr is this:
----------snip-------------------
class TestLexer extends Lexer;
options {
  k=3;
}

DATE  :	'0'..'9'('0'..'9')? '.' '0'..'9' ('0'..'9')? '.' 
('0'..'9''0'..'9''0'..'9''0'..'9')
      { System.out.println("Found DATE:" + getText()); }
      ;

NUM   : ('0'..'9')+(','('0'..'9')+)?
      { System.out.println("Found NUM :" + getText()); }
      ;
----------snip-------------------

I can understand that a lexer with a lookahead of one or two would 
not be able to differentiate between the two token-types, but even 
with a lookahead of three the antlr-Tool gives me the following error 
message:
antlr:
    [antlr] ANTLR Parser Generator   Version 2.7.2   1989-2003 
jGuru.com
    [antlr] C:\PROGRA~1\eclipse\WORKSP~1\PLANKO~2
\src\java\ch\forumedia\rpkc\blah.g: warning:lexical nondeterminism 
between rules DATE and NUM upon
    [antlr] C:\PROGRA~1\eclipse\WORKSP~1\PLANKO~2
\src\java\ch\forumedia\rpkc\blah.g:     k==1:'0'..'9'
    [antlr] C:\PROGRA~1\eclipse\WORKSP~1\PLANKO~2
\src\java\ch\forumedia\rpkc\blah.g:     k==2:'0'..'9'
    [antlr] C:\PROGRA~1\eclipse\WORKSP~1\PLANKO~2
\src\java\ch\forumedia\rpkc\blah.g:     k==3:'0'..'9'

Why is the inputfile nondeterministic? If the third character is a 
digit, it cannot be a DATE-Token!?!

Thanks for any hints,
  Andreas



 
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