[antlr-interest] Beginner grammar question

[Gavin Lambert]

At 19:39 12/09/2008, Fabian Baboschi wrote:
>element    :   BAR NAME
>     ;
>
>BAR    :     'bar'
>     ;
>
>NAME
>     :     ('a'..'z'|'A'..'Z')('a'..'z'|'A'..'Z'|'0'..'9'|'_')*
>     ;
[...]
>I tried to use the following input: bar bar
>and I get errors because the parser doesn't recognize that the 
>second bar should be treated as a name.

The other common solution to this (the first being what Matt just 
suggested) is to leave your BAR rule in place but change element 
like so:

element : BAR name ;
name : NAME | BAR ;


The key point to realise in all of this is that lexing happens 
first, without any parser context.  So given a choice between an 
exact-match keyword and a vague-match identifier rule, the keyword 
will win.