[antlr-interest] To match or not to match

[Raphael Reitzig]

Apparantly, attachments won't work. Sorry for that. 

You can find the grammar file here: 
http://raphael.frhk.de/files/property.g 

For those afraid of viruses or such: 

***** 

grammar property;

start 
	:	property EOF;

property //options { backtrack=true; memoize=true; }
	:	NOT '(' property ')'
	|	( ALL | GLOB | SOME | FIN | NEXT)+ '(' property ')'
	|	'(' property ( (AND | OR) property )+ ')'
	|	('(' atom ')')  => '(' atom ')' 
	|	( atom ) => atom;
	
atom
	:	term (EQ | NEQ | LES | GRT | LEQ | GEQ) term;

term
	:	'(' term (PLUS | MINUS | MULT| DIV | MOD) term ')'
	|	(MIN | MAX) '(' term ',' term ')'
	|	(MINUS)? INT
	|	(MINUS)? VAR
	|	MINUS '(' term ')';

INT 	:	('0'..'9')+;
VAR 	:	('a'..'z') ('a'..'z' | 'A'..'Z' | '0'..'9' | '_')*;

ALL	:	'A';
SOME 	:	'E';
GLOB	:	'G';
FIN 	:	'F';
NEXT		:	'X';

UNTIL 	:	'U';
IMPL 	:	'->';
AND 	:	'&';
OR 	:	'|';
NOT 	:	'!';

PLUS 	:	'+';
MINUS 	:	'-'; 
MULT 	:	'*';
DIV 	:	'/';
MOD 	:	'%';

MIN 	:	'Min';
MAX 	:	'Max';

EQ 	:	'=';
NEQ 	:	'!=';
LES 	:	'<';
GRT 	:	'>';
LEQ 	:	 '<=';
GEQ 	:	 '>=';

WS 	:	(' ' | '\t' | '\n' | '\r')+ { skip(); };

*****

On Fri, 20 Jun 2008 14:52:52 +0200, Raphael Reitzig <r_reitzi at cs.uni-kl.de>
wrote:
> Hello!
> 
> I am quite a novice to ANTLR as well as language parsing at all, so
> perhaps
> I dug in a bit to quickly (got The Book the day before yesterday).
Anyway,
> I try to build a grammar I need for a job at university and get some
> strange results I do not understand. I hope file appendings work on the
> list.
> 
> Using ANTLRWorks' Interpreter, I try to match the following sentence
> against rule 'atom':
> 
> Min(4,3)=x
> 
> It works perfectly. It should match rule 'property' as well (last
> alternative: 'property : ( atom ) => atom;'), but trying that yields
> FailedPredicateException. (I (think I) need the predicates to help LL(*)
> along with multiple '('s in a row.) Exactly why does the predicate become
> false _if_ the checked sequence _is_ an atom?
> 
> Matching Min(4,3) alone against 'term' I expect to work, for it did,
> matching the statement given above against 'atom'. However, it fails
> without exception, aparently not recognizing ',' correctly.
> 
> I would not be surprised I if made a (simple?) systematic error. Can you
> help me?
> 
> Greetings from Germany
> 
> Raphael Reitzig