[antlr-interest] two question about java.g

[lzy7886]

Hi Terence:

I just have two questions about some rules in your java.g example
(antlr-2.7.2\examples\java\java).
First the NUM_INT lexer rule:
please see the //?? part of in the following excerpt .
NUM_INT
	{boolean isDecimal=false; Token t=null;}
    :   '.' {_ttype = DOT;}
            (	('0'..'9')+ (EXPONENT)? (f1:FLOAT_SUFFIX {t=f1;})?
            )?

	|	(	'0' {isDecimal = true;} 
			(	('x'|'X')
				(			
							
	// hex
	options {
					
	warnWhenFollowAmbig=false;
					}
				:	HEX_DIGIT
				)+
			|	('0'..'7')+		

			)?
		|	('1'..'9') ('0'..'9')*  {isDecimal=true;}
		// non-zero decimal
		)
//??here when you enter the follwing subrule whether now you have 
//hex,decimal or oct number,the rule set all the isDecimal variable to
//ture.so the semantic predicates of the isDecimal variable in the 
//beginning of the second alternative of the follwing subrule seems 
//meaningless.
//I wonder if the initial idea is to prevent hex number appended 
//with '.',ie:0x44.0e44
		(	('l'|'L') { _ttype = NUM_LONG; }	
	
		// only check to see if it's a float if looks like 
decimal so far
		|	{isDecimal}?
            		(   '.' ('0'..'9')* (EXPONENT)? 
(f2:FLOAT_SUFFIX {t=f2;})?
            		   EXPONENT (f3:FLOAT_SUFFIX {t=f3;})?
            		|   f4:FLOAT_SUFFIX {t=f4;}
            		)
            		{
			if (t != null && t.getText().toUpperCase
() .indexOf('F') >= 0) {
                		_ttype = NUM_FLOAT;
			}
            		else {
	           	_ttype = NUM_DOUBLE; // assume double
			}
			}
        	)?
The second question is that I found in the java spec 2rd:
It is a compile-time error for a line terminator to appear after the 
opening ' and before the closing '.(chapter 3.10.4) 
It is a compile-time error for a line terminator to appear after the 
opening " and before the closing matching ".(chapter 3.10.5)
But the corresponding lexer rule in java.g doesn't abide by the spec :
// character literals
CHAR_LITERAL
	:	'\'' ( ESC | ~'\'' ) '\''
	;

// string literals
STRING_LITERAL
	:	'"' (ESC|~('"'|'\\'))* '"'
	;
One proposal for revision: 
// character literals
CHAR_LITERAL
	:	'\'' ( ESC | ~('\''|'\n'|'\r') ) '\''
	;

// string literals
STRING_LITERAL
	:	'"' (ESC|~('"'|'\\'|'\n'|'\r'))* '"'
	;	
OK,that's all my question so far,anyway ANTLR is just so wonderful!I 
appreciate you guys work a lot.I am looking forward to 
the progress of this revolutionary tool.

                        One guy from China
                                 lzy	
        	



 

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