Re: Clean Object Class Design -- Circle/Ellipse

From: Bob Badour <bbadour_at_golden.net>
Date: Fri, 31 Aug 2001 22:32:38 -0400
Message-ID: <TMXj7.616$fs4.124486743_at_radon.golden.net>


[Quoted] James A. Robertson wrote in message <3B8A67F0.CA3FDC42_at_mail.com>...
>Bob Badour wrote:
>>
>> >Since Smalltalk *has* instances that are values (the number
>> >5 comes mind)
>
>This is trickier in Smalltalk. Why? because instances of classes are
>objects, and classes (and metaclasses) are also objects. The bottom
>line is that in Smalltalk, <everything> is an object.

I don't see how that changes anything. Classes are instances of metaclasses and classes can change over time, which make them variables of metaclasses. At any point in time, a class has a metaclass value.

Not everything in Smalltalk is a variable and not everything in Smalltalk is a value.

>> Hmmm... I have been looking for Smalltalk's definition of the term
>> "instance". So far, all of the definitions seem to equate the term
instance
>> with the concept of variable:
>>
>> From http://www.wi2.uni-erlangen.de/sw/smalltalk/glossary.html
>>
>> instance: An object that is a single occurrence of a particular class. An
>> instance exists in memory or external media in persistent form.
>
>Variables in Smalltalk are nothing more than references to some object.
>That object can be anything

Named variables in Smalltalk are nothing more than references to variables. The referenced variables have values, but they cannot *be* values. Received on Sat Sep 01 2001 - 04:32:38 CEST

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