Re: Clean Object Class Design -- Circle/Ellipse

"Graham Perkins" <gperkins_at_dmu.ac.uk> wrote in message news:3BB84321.B44CF13E_at_dmu.ac.uk...
> Bob Badour wrote:
> > > I know Smalltalk more than a little well.
> > > And James Robertson (who knows a thing or
> > > two about Smalltalk :-) agreed with me that you
> > > were incorrect.
> >
> > Big deal. Ask him to point to any Smalltalk language definition that
defines
> > "instance" as anything other than a variable which one can reference.
>
> Well for starters the following three descriptive pages each contain
> many desriptions of "objects" and "instances of classes", all of which
> are clearly shown to exist independently from variables.
>
> http://www.mucow.com/squeak-qref.html

The above page uses variable and instance equivalently. You may want to read it more carefully.

> http://kaka.cosc.canterbury.ac.nz/~wolfgang/cosc205/smalltalk1.html

The above page uses instance to mean variable and variable to mean any named variable all of which contain pointers to variables.

> http://www.objs.com/x3h7/smalltalk.htm

The above page uses instance to mean variable and variable to mean "any named variable containing a pointer to a variable" or "a pointer to a variable".

> I wonder if perchance you are confused between "instance" and "instance
> variable"?

Nope. An instance has instance variables which define the state of the instance. Variables have state. Values are state.

> The latter, of course, is smalltalk terminology for what
> others call an "attribute". Yes, an instance variable, being an
> attribute,
> is certainly a (scoped) variable that one can reference.
> (tho' even so you'd still be wrong since the reflection capabilities
> allows the programmer to access it as an offset rather than a variable)

LOL. You have clearly demonstrated that instances are variables.

> > An instance or variable can have the value 5. The value, however,
> > is not an instance.
>
> It's an instance of SmallInt, as you can easily discover
> by inspecting it (inspector window normally puts the class
> on its title bar).

The variable that contains the representation of the value 5 is an instance of SmallInt. The value 5 is a value and not an instance.

> From within its inspector window, you
> can send it any message that is handled by the SmallInt protocols,
> and it will respond as if it were an instance of the class SmallInt.
> Which indeed it is.

Yes, the variable is an instance of SmallInt.

> > According to the definition of the Smalltalk language an instance
> > is a variable that one can reference. One cannot reference a value.
> > Values are self-identifying.
>
> This is simply untrue, and it couldn't possibly make sense.
> Mr Badour is clearly confused about the concepts of variable,
> value, reference, object, class, and instance.

If you honestly believe that one can reference a value, I must observe that I am not the confused one.

> > Anyone with access to a browser and Google can verify for
> > themselves that Smalltalk defines "instance" as a variable
> > that one can reference.
>
> The three links above contradict you. I found them in 2 mins
> with Google.

Except that the three links confirm my point and contradict those who claim that instances can be values. Apparently, it only took you 2 mins to verify my point.

> > ..you have no interest in learning or in
> > communicating -- instead, you have an interest in attacking and
> > destroying. I find little merit in your goals.
>
> I cannot see how Bob Badour can make such a claim. He has made
> a bunch of completely untrue assertions and refuses to accept
> quite reasonable explanations from people with reasonable
> communication skills. It should be obvious to whom the comment
> "no interest in learning or in communicating" really applies.

What reasonable explanation? Where? Someone making a false assertion that some instances are values does not communicate anything. I can see now that Smalltalk is much worse than C++. Apparently, Smalltalk has closer ties to Newspeak than any programming language I have ever seen. Smalltalk practitioners have lost the ability to even properly conceive of values and variables. Received on Sun Oct 07 2001 - 03:01:10 CEST