[antlr-interest] Newbie: NoViableAltException

Buck, Robert rbuck at verisign.com
Tue Jul 24 13:50:49 PDT 2007


Hi,

(foo=bar)
     ^

A "NoViableAltException(0!=[null]) exception occurs at 'bar', given the
following grammar. Not quite sure why. I did not understand this one.
What could be happening?

Thanks in advance,

Bob

#####################

prog
	:	tuple
	;
tuple
	:	L_PAREN tuple_decl EQUALS ( tupleValue | set ) R_PAREN
	;
set
	:	L_CURLY tuple ( COMMA tuple )*
	;
tuple_decl
	:	tupleKey ( tuplePI )? 
	;
tuplePI
	:	AT_SIGN set
	;
tupleKey
	:	IDENT
	;
tupleValue
	:	( PCHAR )*
	;

/*------------------------------------------------------------------
 * LEXER RULES
 *------------------------------------------------------------------*/

PCHAR
	:	PCT_ENCODED | UNRESERVED
	;
IDENT
	:	LETTER ( LETTER | UNDERSCORE | HYPHEN | DIGIT)*
	;
L_PAREN
	:	'('
	;
R_PAREN
	:	')'
	;
L_CURLY
	:	'{'
	;
R_CURLY
	:	'}'
	;
COMMA
	:	','
	;
EQUALS
	:	'='
	;
AT_SIGN
	:	'@'
	;
HexLiteral
	: '0' ('x'|'X') HEXDIGIT+ 
	;
fragment UNRESERVED
	:	LETTER | DIGIT | '-' | '.' | '_' | '~' | ':'
	;
fragment PCT_ENCODED
	:	'%' HEXDIGIT HEXDIGIT
	;
fragment HEXDIGIT
	:	( DIGIT | 'a'..'f' | 'A'..'F' )
	;
fragment LETTER
	:	('a'..'z')|('A'..'Z')
	;
fragment DIGIT
	:	'0'..'9'
	;
fragment L_BRACKET
	:	'['
	;
fragment R_BRACKET
	:	']'
	;
fragment UNDERSCORE
	:	'_'
	;
fragment HYPHEN
	:	'-'
	;


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