[antlr-interest] Java.g grammar issues & potential fix

[Vincent Mallet]

Terence & All,

A problem in Clover (code coverage for Java which uses antlr)
prompted me to look at the java.g "1.4 update" grammar and I found
a few problems with the lexer:
 1. the grammar won't accept octal-looking floats or doubles 
    (09d for example) 
 2. the grammar will accept hexadecimal numbers with a fractional
    part (0x12.34 for example)

I have seen a fix for problem #1 in java.g version 1.21-october-2003
but #2 is definitely broken.

In an attempt to clarify that part of the grammar I came up with a
version of the NUM_INT lexer rule which seems to be more correct and
potentially easier to read (indentation might need some work).

If you have an opinion on the new rule I would love to hear it.

Here it goes:
take java.g, truncate evertyhing after "NUM_INT", replace with:


 ---cut-cut---
// a numeric literal
NUM_INT
    :   // all floating point literals with a whole-number part
        ( (DIGIT)+ ('.' | 'e' | 'E' | 'f' | 'F' | 'd' | 'D' ) )=> 
(DIGIT)+
        (  (('.' (DIGIT)* (EXPONENT)? | EXPONENT )
            (('f'|'F') { _ttype = NUM_FLOAT; } | ('d' | 'D')? { 
_ttype = NUM_DOUBLE; } )
           )
         | ( ('f'|'F') { _ttype = NUM_FLOAT; } ) 
         | ( ('d'|'D') { _ttype = NUM_DOUBLE; } )
        )

    |   // all floating point literals with no whole-number part 
(possibly just '.')
        '.' { _ttype = DOT; }
        (DIGIT)+ (EXPONENT)?        
        ( ('f'|'F') { _ttype = NUM_FLOAT; } | ('d' | 'D')? { _ttype 
= NUM_DOUBLE; } )
        
    |   // all decimal literals
        (   '0' ('0'..'7')+              // octal
          | ('1'..'9') (DIGIT)+          // decimal
          | '0' ('x' | 'X') (HEX_DIGIT)+ // hexa
          | '0'                          // decimal
        )
        (('l' | 'L') { _ttype = NUM_LONG; })? 
    ;


// a couple protected methods to assist in matching floating point 
numbers
protected
DIGIT
	:	'0'..'9'
	;

protected
EXPONENT
	:	('e'|'E') ('+'|'-')? ('0'..'9')+
	;

 ---cut-cut---

Thanks,

    Vince.








 
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