All you need do is use a predicate at the DOT, which is where the esPred rule
is. You can change the syntactic predicate to a semantic predicate and check
for #, ., ( and : via input.LT() but can also look at the previous token even
if off channel to make sure it is not a space:
simpleSelector
: elementName
({ mySemPred() }?=>elementSubsequent)*
| ({ mySemPred() }?=>elementSubsequent)+
;
@parser:members {
boolean mySemPred() {
switch (input.LA(1)) {
case DOT:
// Only if no preceding spaces (but is that correct for CSS?
//
if ((TokenStream)input).get( input.index()-1 ).getType() != WS) {
return true; } else {return false; }
break;
case HASH:
case LBRACKET:
case COLON:
return true;
default:
return false;
}
}
> -----Original Message-----
> From: [email protected] [mailto:antlr-interest-
> [email protected]] On Behalf Of David Grieve
> Sent: Monday, January 18, 2010 12:29 PM
> To: [email protected]
> Subject: [antlr-interest] Detecting a space as a token
>
> In CSS, a selector is (roughly) a sequence of simple selectors joined
> by a combinator. http://www.antlr.org/grammar/1240941192304/css21.g has
> the following rules which correspond to this.
>
> combinator
> : PLUS
> | GREATER
> |
> ;
>
> selector
> : simpleSelector (combinator simpleSelector)*
> ;
>
> The issue I'm having is how to handle the combinator which is a space
> in the selector rule. Specifically, I should be able to parse
>
> A .b
>
> as two simple selectors: A and .b. However, since whitespace is
> ignored, this is getting parsed as one selector. The following parses
> as desired:
>
> A *.b
>
> Using the universal selector as part of the second simple selector is a
> workaround that I shouldn't have to employ.
>
> How can I parse "A<space>.b" such that the space is recognized as a
> combinator? Thanks in advance for any help!
> David Grieve
> Sun Microsystems, Inc.
>
>
>
>
>
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