[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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