[antlr-interest] Lexer question
John B. Brodie
jbb at acm.org
Tue Aug 23 14:57:40 PDT 2011
try
rule1: IDENTIFIER ':' expression ;
that is why bother differentiating the two tokens?
On Tue, 2011-08-23 at 21:19 +0000, Scott Smith wrote:
> I have a parser that is doing pretty much what I want. However, I want to do the following.
>
> I have a definition for an IDENTIFIER
>
> IDENTIFIER: LETTER (LETTER | NUMBER) // LETTER and NUMBER mean the usual thing
>
> Now in some of my rules, I'm looking for an IDENTIFIER and in one of my rules I look for a NAME. NAME has exactly the same definition as IDENTIFIER (starts with a letter followed by alphanumerics). However, you can tell by the token after whether it was a NAME or an IDENTIFIER. To be more explicit, a NAME is ALWAYS followed by a colon. An IDENTIFIER can be followed by a number of things, but NEVER by a colon.
>
> So, I have rules that looksomething like:
>
> rule1:
> NAME ':' expression
> ;
>
> rule2:
> IDENTIFIER '+' expression
> | IDENTIFIER '-' expression
> ;
>
> I don't seem to be able to make this work. Can someone suggest a solution? Do I have to turn on backtracking to make this work?
>
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