[antlr-interest] Re: Building hierarchical grammars

[Mark]

> LITERAL:    INTEGER_LITERAL | FLOATING_POINT_LITERAL | CHARACTER_LITERAL | 
STRING_LITERAL;

These things should be parser rules, not lexer rules.

literal: INTEGER_LITERAL | FLOATING_POINT_LITERAL | CHARACTER_LITERAL | 
STRING_LITERAL;

In general, Lexers are not 'hierarchical', Parsers are.  Different parser rules can match 
similar things because they are called from other rules:

array-assignment: ID "[" index "]" "=" value ";' ;
index: INTEGER_LITERAL  ;
value:  INTEGER_LITERAL | FLOATING_POINT_LITERAL ;

Lexers, on the other hand, have to pick from among ALL the Lexer rules each and every 
time they are asked for the next token.  They don't 'know' where they are called from in 
the parser, and so can't restrict the set of token parses for a particular case.

- Mark




 
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