[antlr-interest] Syntactic predicates (in reverse)

[Paul J. Lucas]

First, in the lexer documentation for the example for Pascal INT, REAL, or range, RANGE_OR_INT is never used.

Second, what I'm looking to do is match backwards in addition to forwards.  For example, consider:

	define function foo

in some language.  "define" and "function" should be returned as keywords DEFINE and FUNCTION respectively, but only if they occur together; otherwise IDENTIFIER for each.

Using the FORTRAN DO loop from the lexer documentation as a guide, I can do:

	DEFINE
		: (DEFINE_FUNCTION)=> "define"
		;

	protected DEFINE_FUNCTION
		: "define" FUNCTION
		;

	FUNCTION
		: "function"
		;

This (I believe) will correctly return the DEFINE token to the parser only of "define" is followed by "function."  But how can I get the lexer to return FUNCTION as the next token, but only if it was *preceded* by "define"?

- Paul


 

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