[Grace-core] Duck TYping at PoPL

[James Noble]

> Ys, we don't want to permit that.  But what about taking an entry out of a dictionary and applying it, as a block, to the remaining entries in the dictionary.  Perfectly normal dynamic language stuff.

now that's a really good question: basically what should the types of dictionaries look like? 

homogeneous (as in Java "Generic" Maps?) or heterogenous (as in Grace Objects)?
I've been assuming (as in most gradual/hybrid typed systems, including Strongtalk,
DRuby, we wouldn't have dependently typed Maps. DRuby has tuple types
that may convert into array disjunction types (Tuple<T1, T2, T3> 
is treated as Array<T1 | T2 | T3>).  But this is clearly something we need to think about.

But, perhaps once we've got the basic type system for Grace going...

James