Q: Hash store

[Leopold Toetsch]

While implementing freeze/thaw I come - again - to this issue. Currently 
a HASH can store arbitrary and in one hash mixed items. This is done by 
storing an union with a type field.
(List based) arrays on the other hand only have one fixed type per 
aggregate (e.g. ints for IntList or PMCs for Array) - defined at list 
creation time.
So the question is:
Do we need/want to keep this mixed entry store for hash or switch over 
to the same scheme used in arrays?

leo