Identity and Inheritance was: (Re: [BUG] Set>>collect:)
Richard A. O'Keefe
ok at cs.otago.ac.nz
Mon Feb 17 00:17:19 UTC 2003
Bill Spight <bspight at pacbell.net> wrote:
In this discussion it has struck me that IdentitySet, although
it is a child of Set, is a generalization of it, since it allows
elements that Set does not. Maybe it should not inherit from Set, but
the other way around.
Inheritance in Smalltalk is primarily about code reuse, NOT generalisation.
It is not really true that IdentitySet is a generalisation of Set;
what it does with the elements is different from what Set does.
In a generalisation/specialisation sense,
the hierarchy should be
<Generic Set> "missing"
<Generic Bag> "missing"
If Smalltalk inheritance was about generalisation/specialisation,
we wouldn't have Dictionary inheriting from Set.
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