31 Jul
2002
31 Jul
'02
4:57 a.m.
Keith Wansbrough wrote:
I wish "keysFM" would yield "Set key" rather than "[key]"!
IIRC a Set key is simply a FiniteMap key key. So what you require is simply a mapFM (\k v -> k).
Set is an abstract data type , that can be viewed as a sorted list without duplicates (or as a special mapp, see below). Simply in order to document that property "keysFM" should return "Set key"! You're suggestion "mapFM (\k v -> k)" yields a "FiniteMap key key". The internal representation, however, is (by mere coincidence) "FiniteMap key ()", so "mapFM (\k v -> ())" would be a correct implementation, but only if I knew the internal representation of a set and could use the hidden constructor for Set.
Correct me if I'm wrong...
I hope I did, Cheers Christian