Does it make sense to remove slots ?

[Massimo Dentico]

"Tim Moore" <Timothy at Moore.name> wrote:

> 
> I don't know about "sacred dogma" but I would say that it is generally  
> a good idea.

On what ground do you accept this "principle"? How *behavioral* equivalence
is relevant in this case where you clearly want subtyping, ie. you want
to constraint a slot *value* to be in a well defined subset? (My assumption
is that this is what Pupeno want: Pupeno, please, correct me if I'm wrong).


>>> Long story short: Todd is right. Circle shouldn't be derived from  
>>> Ellipse unless they're both immutable, and most likely you don't  
>>> really need a Circle type at all.
                  ^^^^^^^^^^^

>> Please, explain what does it mean to mutate a *value*.
>>
>> A *value* is immutable by definition; what you can mutate
>> eventually is a *variable*. In the context of a prototype-based
>> languages as Slate, slots are variables.
> 
> I'm sorry, but I don't really understand what you're getting at. What  
> I'm saying is that if Circle and Ellipse are immutable (i.e., the slots  
> don't change after construction and the whole object acts as a  
> conceptual value) then there are no problems. However if you do allow  
> the axis lengths to change (i.e., the classes function as variables)  
> then you can run into problems.

I'm saying that until a clear definition of what to mean
for a prototype to be "a type" and, in this context, of
what "derivedFrom:" means, confusion is granted.

 
>> Besides this, I agree with Peter van Rooijen: if you decouple
>> the concept of inheritance/subclassing from that of subtyping
>> (IIRC as in Sather http://www.icsi.berkeley.edu/~sather/) the
>> problems vanishes:
>>
>> - subtyping means:  if A is a subtype of B, then A is a subset of B;
>> - inheriting means: if A inherit from B, then part/all of the structure
>>                    and/or behavior of B is *included* in (inherited  
>> by) A.
> 
> How would that apply here?

I was commenting Peter here. How this apply to Slate depends from
how you set the preceding definitions.

Regards.

P.S.: I hope that my English is understandable here.

-- 
Massimo Dentico