On Sat, Dec 5, 2009 at 2:00 AM, Stéphane Ducasse
<stephane.ducasse at inria.fr>wrote:

> http://lambda-the-ultimate.org/node/3702
>


I want to return to the implementation and optimization implications of this
later.  But Steele's post refers to William Cook's excellent paper On
understanding data abstraction, revisited. Onward! Essays, 2009 ACM OOPSLA.
SIGPLAN Notices 44, 10 (Oct. 2009), 557-572. There's a freely available draft
version <http://www.cs.utexas.edu/~wcook/Drafts/2009/essay.pdf>.  The quote
I want to emphasise is

The extensibility of objects does not depend upon inheritance, but rather is
an inherent property of object interfaces.


The paper proves this point eloquently and concisely.  The implication is
that isKindOf: is <shout>*BROKEN</shout>*.  In the absence of something
better isSomeInterface to query whether an object implements some interface
SomeInterface is acceptable.  isKindOf: (and the horror I found the other
day isKindOf:orKindOf: (you see why it exists and where it leads?)) is not
and should be expunged.

My weekend rant.

best,
Eliot
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