How do you define "object-oriented"?
Alan Kay
Alan.Kay at squeakland.org
Sun Apr 28 16:32:07 UTC 2002
Just for the record ....
In Smalltalk-72, variables were theoretically objects, and thus
required quoting in order to do assignment. So
'a meant give me the symbol a
BTW " ' " is an actual object in Smalltalk-72
a meant give me the value that is
associated with the symbol a
the symbol a would look itself up in
the current context to find the value
'a <- foo meant send the message "<- foo" to the symbol a
which would look itself up in current
context and store the value
a <- foo meant send the message "<- foo" to the object
associated with the symbol a
etc.
In retrospect, it might have been a better idea to use the opposite
convention instead of one that worked like LISP -- so a symbol would
be a literal (like a number), and there would have been a message to
get the value associated with it. But maybe not ...
Also, a number of inheritance ideas were tried out in Smalltalk-72,
none of which I liked all that much. My favorite were the "slot
inheritance" experiments that were done by Larry Tesler.
Cheers,
Alan
-------
At 8:40 AM -0700 4/27/02, Dan Rozenfarb wrote:
>Jecel Assumpcao wrote:
>> I don't see any practical difference
>> between "inheritance" and "delegation"
>
>Me neither. I pointed that out just to make a
>difference between
>what Self has and what is commonly referred by
>inheritance
>(including Wegner=B4s classification), that is, Class
>Inheritance.
>Anyway, I see inheritance as a useful, although not
>mandatory
>feature.
>
>
>> > With this definition, Smalltalk is not *pure* OO.
>>
>> Because of the classes? See "Smalltalk with
>Examplars" or CoDA for
>> Smalltalks with classless objects.
>
>No. With "definition" I meant the previous one:
>"Objects
>communicating through message passing".
>One example: Smalltalk accesses variables directly,
>not by message
>passing. OK, it=B4s not a big deal, but illustrates
>my point.
>
>
>> But I prefer not to fight for any particular meaning
>of "OO"
>
>I tend to agree. It is not all that important having
>an exact
>definition. But my scientific spirit makes me love
>the purist
>approach that led to great research pursuing a clean
>and pure OO
>(such as the Self project). This utopic and
>minimalist sense is
>much related with simplicity, that is one of the
>things I love the
>most about objects, and what IMHO made Smalltalk what
>it is.
>
>Regards,
>Dan Rozenfarb
>
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