> I've taken a look and I agree it looks powerful. The embedding in the 
> language is crucial to what they are trying to do: making 
> grammars/parsing a first-class entity in the language that plays nicely 
> with the other parts. The things that is a bit hard to understand is how 
> powerful a parser this can be used to express. All context-free 
> grammars? An even larger class? I guess the latter might be the case 
> since they can have code intermingled.
> 
> The downside is the complexity of it, both in understanding and 
> implementing. Do they plan to support this in Parrot so that other 
> languages on top of Parrot can reuse the same implemenation? Seems like 
> this is quite a bit away into the future. Thanks for bringing it up.
> 
> /Robert
> 
> 
> 
> 
I don't think it's built into parrot, but perhaps I am mistaken, mostly 
it seems like more of syntax issue then a interpreter issue.  I think 
they may have some sort of adhoc equivalent as a module for perl5, not 
sure how they are getting calls from within the regex, but they may be 
doing some funny crap with perl c extensions.  In classic perl manner 
the syntax they describe for it is definitely pretty pregnant with 
symantics, and very overloaded.  However it seems as if the gist could 
be streamlined, and made into a more ruby esque form, without loss of 
generality.

Maybe if the next regex engine for ruby had some sort of embeddable code 
block, then something like this could be implemented as a module, 
ensuring it was true to existing syntax and symantics.

Unfortuneatly I don't really like embeddable code blocks in a regex 
unless it is through a grammar syntax, as it seems like a more difficult 
concept to grasp then the .. and ... operators.  Definitely something 
that needs more discussion though I believe.

Charles Comstock