Re: A bad counterintuitive behaviour of Ada about OO

[Victor Porton <porton@narod.ru>]

Dmitry A. Kazakov wrote:

> On Fri, 08 Aug 2014 12:01:48 +0200, J-P. Rosen wrote:
> 
>> Le 08/08/2014 11:13, Dmitry A. Kazakov a écrit :
>>> How mathematics may not apply to the elementary types like Integer?
>> Because computer integers are not the same as mathematical ones, and the
>> way they are used are different.
> 
> Interesting, it was always OO proponents' argument that numbers are not
> numbers.
>  
>> Moreover, classification is used in mathematics for the theory of
>> numbers, which is not relevant to practical usage of numbers.
> 
> Having integers ordered is unpractical? Being them additive has no usage?
> 
>>> Do you propose not to formalize "some features"? This is not how Ada
>>> generics work anyway. "Some features" are formalized in Ada through
>>> formal generic parameters. The only difference to classes is that
>>> classes do that through types, while generics do in an untyped manner.
>> 
>> And those types must be related through inheritance, while generics may
>> be instantiated on types that have no conceptual relationship.
> 
> I don't know which relationships are "conceptual" and which are not.
> 
> generic
>    type Element_Type is private;
>    with function "<" (Left, Right : Element_Type) return Boolean is <>;
>    with function "=" (Left, Right : Element_Type) return Boolean is <>;
> package Ada.Containers.Ordered_Sets is
> 
> Isn't all types acceptable as Element_Type a "conceptual" class?

Making elementary classes would certainly require multiple inheritance (and 
even "virtual" multiple inheritance, in C++ terms).

I think it would be very hard to modify Ada standard to support this.

-- 
Victor Porton - http://portonvictor.org