
7 Dec
2001
7 Dec
'01
6:56 p.m.
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=...