[antlr-interest] wildcard in tree grammar

[Sam Harwell]

That should be correct, but under the current implementation, I believe
it will match any tree with the . wildcard, then find 0 instances of
tree. The problem doesn't occur in the rule you have here, but this rule
will only print 1 line, regardless of the input tree:

tree : ^(. {System.out.println("tree node");} tree*)

Sam

-----Original Message-----
From: Oliver Zeigermann [mailto:oliver.zeigermann at gmail.com] 
Sent: Thursday, November 27, 2008 2:24 AM
To: Gavin Lambert
Cc: Terence Parr; Sam Harwell; antlr-interest Interest
Subject: Re: [antlr-interest] wildcard in tree grammar

2008/11/27 Gavin Lambert <antlr at mirality.co.nz>:
> In other words (in vaguely ANTLR-like syntax):
>
>   wildtree : ANYNODE | ^(ANYNODE wildtree*) ;
>
>   .          => wild
>   ^(.)       => ANYNODE
>   ^(. FOO)   => ^(ANYNODE FOO)
>   ^(FOO .)   => ^(FOO wildtree)
>   ^(FOO . .) => ^(FOO wildtree wildtree)
>   ^(FOO .+)  => ^(FOO wildtree+)
>   ^(FOO .*)  => ^(FOO wildtree*)

Using these semantics my original rule

tree : ^(. tree* ) ;

would match any tree even if subtrees are single nodes only, right?

Oliver