[antlr-interest] Getting the Previously Matched Lexer Token in the C Target

[Kirby Bohling]

If you aren't going to lex that token to something else, I'm pretty
sure the right solution is to just lex it as the invalid token.  If
you are going to lex it to something else, then likely you have the
"keyword" vs. "id" problem (use one token for it in the lexer, and
pick which one it really is during parsing).  Which I believe is best
resolved by a gated predicate in the parser.  If it "looks" like legal
code, you'd be better of actually generating the error at the semantic
check phase.  You have a lot more context in order to generate a
useful error message at that point.

Kirby


On Mon, Jul 19, 2010 at 7:23 PM, Billy O'Neal <billy.oneal at gmail.com> wrote:
> Hello, Everyone :)
>
> Was referred here from my StackOverflow question:
> http://stackoverflow.com/questions/3278338/using-the-antlr-c-target-how-can-i-get-the-previously-matched-token-in-the-lexer
>
> I'm quite new to ANTLR; and my Lexer needs to have a gated rule which
> makes it valid if and only if it occurs directly after another rule.
> If there's a way to get the previously emitted token type, that would
> make that gating easy. Otherwise I have to fail over to a nasty hack
> of turning the boolean flag off after every lexer rule.
>
> Is it simple/easy to get that information in a lexer rule predicate?
>
> Billy3
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