instance declarations

[David Feuer]

I am curious about a couple things regarding instance declarations.

1.  Why can't they be hidden in module imports/exports?  Is this an
implementation issue (I guess I could see it as a problem with the
dictionary-passing approach...)?  It seems kind of bad that instances are
not allowed to overlap, but can't be hidden.

2.  Why can't you simultaneously declare a type to be an instance of
multiple classes?  i.e, why can't you write the following?

class C1 t where
	a::t->t
class C1 t => C2 t where
	b::t->t

instance C1 t, C2 t where
	a=...
	b=...