[Grace-core] some thoughts on structural types & pattern matching

[James Noble]

>>> Being able to ask whether or not a message will be understood is another.  Typecase does the latter, does it not?
>> 
>> yep, that's pretty much it. 
> 
> So it should be flagged as "Meta" ?

ay, there's the rub - that's what we're trying to decide.

The simplest thing that could possible work in an (un/dynamically) typed language
would be to give every object a match( key ) method, which returns a Boolean if the 
object conceptually should "match" the "key", and an "extract" method that returns 
a tuple for any destructuring binding. 

class Object { 
  method match( k ) { k == "Object" }
  method extract { [] }   // empty typle
}

class Point { x, y ->
  method match( k ) { (k == "Point") || {super.match( k )} }
  method extract { [x,y] } 
}


where's the meta in that?

is there still meta-ness if the class form somehow generates the "match" method (as it does with ==) 

James