[antlr-interest] Lexer rule problem - ANTLR 2.7.7

[Jim Idle]

Clive,

 

This should help you:

 

http://www.antlr.org/pipermail/antlr-interest/2007-October/024345.h
tml

 

Except in that example use COLON rather than a separate RANGE token.

 

Jim

 

From: clive.i.hill at jpmorgan.com [mailto:clive.i.hill at jpmorgan.com] 
Sent: Thursday, January 31, 2008 8:36 AM
To: antlr-interest at antlr.org
Subject: [antlr-interest] Lexer rule problem - ANTLR 2.7.7

 


Hi, 

I have a lexer rule that is meant to match a range of integers or
numbers in the following style format: 

5800:6000 
or 
1.8:2.0 

The lexer rule I have for this is given by: 

protected 
RANGE       
    : (INT | FLOAT) COLON (INT | FLOAT) 
    ; 

where INT,FLOAT, DIGIT, DOT and COLON are given at the end of this
email. 


When I run my parser against the grammar file (attached) with the
following string: 

"ftse dec 5800:6000 c" 

I get the following exception: 

antlr.TokenStreamRecognitionException: expecting '.', found ':'



This is because the lexer is attempting to parse a RANGE token
correctly, but is expecting a FLOAT.  My RANGE lexer rule,, it seems to
me, should check for an INT or  a FLOAT. 

This rule seems very uncomplicated, so I can't tell why it is going
wrong.  Can anyone provide any suggestions? 


Thanks in advance, 

Clive 




protected 
FLOAT       
    : DOT INT 
    | INT DOT (DIGIT)* 
    ; 

protected 
INT         
    : (DIGIT)+ 
    ; 

protected 
DIGIT       
    : '0' .. '9' 
    ; 

COLON 
        : ':' 
        ; 

protected 
DOT         
    : '.' 
    ; 



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