[antlr-interest] Keywords not context-free

[Clifford Heath]

In a grammar I'm working on, I have a significant subset of the
language that allows arbitrary-length strings of identifiers,
where words that are keywords elsewhere (like "is") may be used
as regular identifiers.

Is there a general way to handle this kind of context-sensitivity
in ANTLR (as in, backup and retry if the grammar reports an error),
or must I explore traditional methods of informing the lexer?

Also, can someone point me to a brief synopsis of the ANTLR method
of handling lexical contexts. I don't have the book yet, so I'd
like an online source.

Clifford Heath.