It can happen most probably due to problems of hash code. Two objects that are equal SHOULD have same hash code. - either YourObject does define #= but does not define #hash - or you add theObject to theSet, then modify theObject, which has side effect of modifying its hash code, and then theObject cannot be found in theSet (in which case you have a cure: theSet rehash)

scanFor: seems to do the right thing: find a slot corresponding to theObject hash, and look further if this slot is already occupied by anotherObject. If storage is sparse enough and hash code are well distributed, this should lead to an efficient access cost near O(1), while Array includes: use a linear search O(n).

Nicolas

Hilaire Fernandes a écrit :

How can the following happen ?

theSet includes: theOnject -> false theSet asArray includes: theObject -> true

previous sent messages to theSet were add: remove:ifAbsent:

The Set>>ScanFor: looks strange.

Hilaire