[antlr-interest] "become root" operator ^ sometimes fails

[Jim Idle]

On Tue, 2008-10-14 at 14:59 +0200, Mark Langezaal wrote:

> Uhh, subtitles please...
> Do you mean this is a kind of a bug, but there is an easy workaround by
> removing the brackets?
> 



> >> // Input: 1 + 2
> >> // Generated AST: ^(+ 1 2)
> >> okExpr
> >>   :    NUM (('+'|'-')^ NUM)*



basiaclly, I think you want:

NUM ((('+')^|('-')^) NUM)*

You can also do:

NUM (arithOp^ NUM)*;

arithOp : '+' | '-' ;


Though I personally would get rid of all the literals in the parser
grammar and replace them with lexer tokens.

Jim
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