Question

I was told that one has to sort them into SortedCollection, but the Set elements are not comparable (only identity compare, which i dont know how to use for sorting).

So is it safe to compare them like set1 = set2, or do i need to sort them (how for identity?).

I was thinking about some sortblock like this: [:pre :succ | pre OID < succ OID], would that work?

Answer 1

How about

(set1 size = set2 size) and: [set1 includesAllOf: set2]

Depending on the Smalltalk implementation, you might also use =. For example, in Squeak it is implemented like this:

= aSet
    ...
    self size = aSet size ifFalse: [^ false].
    self do: [:each | (aSet includes: each) ifFalse: [^ false]].
    ^ true