[antlr-interest] Rewrite with predicate -> default?

[Terence Parr]

i think "-> ..." works with 3 dots.
T
On Jul 23, 2011, at 1:05 PM, Tobias Diez wrote:

> Hi,
> 
> It is possible to rewrite something based on a predicate but not always?
> What I want to do is the following (pseudo code)
> 
> ^(TOMATCH)
> 	-> ^(RESULT1)   if TOMATCH.Text = 1
> 	-> ^(RESULT2)   if TOMATCH.Text = 2
> 	LEAVE IT UNCHANGED otherwise
> 
> The closest thing I could archive is the following code, which works in the
> sense that the output-AST is correct. But this solution has the flaw that
> ANTLR apparently thinks something has changed and reruns the rule (and
> because nothing changed so far it match again) and so ACTION would be called
> two times!
> 
> command_single_argument
> 	: ^(COMMAND c=CONTROL_WORD ^(BLOCK b=.)) {ACTION}
> 		-> {$c.Text == @"\begin"}? ^(ENVIRONMENT_BEGIN $b)
> 		-> {$c.Text == @"\end"}? ^(ENVIRONMENT_END $b)
> 		-> ^(COMMAND $c ^(BLOCK $b))
> 	;
> 
> Is there a better solution?
> 
> Thanks!
> 
> 
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