On Friday 05 December 2008 07:46:10 Kenny Leung wrote:
> Hi All.
>
> One of the interesting things I found was that this is legal:
>
> NUMBER : '0'..'9';
that's a lexer rule
> but this is not:
>
> number : '0'..'9';
that's a parser rule, the ".." syntax is only allowed in lexer rules.
> Is there a way I can say, "use tokenizer rule A after the "{", but use
> tokenizer rule B after the "=".
for context switching the lexer, I have two ideas (which both may be wrong
:-) ) :
let the lexer allways return charaters as token and combine them in parser
rules like (examples):
id: LETTER (LETTER | DIGIT )*
type_id: I | D | S | CARET | V
type_encoding = LEFT_BRACE id EQUAl type_id+ RIGHT_BRACE
or try a syntactic predicate in the lexer like:
fragment ID: LETTER (LETTER | DIGIT)*
NAME: ;
TYPE: ;
EQUAL:;
V:;
NAME_or_TYPE:
(ID '=') => ID { type = NAME; }
| '=' { type = EQUAL; }
| 'v' { type = V;}
...
but I don't know if this works in nested cases.
Michael
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