Re: In precision typing we trust

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2025-08-28 10:50, Kevin Chadwick wrote:
> 
>>
>> I can explain how it works. When a DLL is loaded its library level 
>> gets elaborated. So if you have:
>>
>> package P is
>>    type T is tagged ...
>> end P;
>>
>> in the main program or DLL and
>>
>> with P;
>> package Q is
>>    type S is new T with ...
>>    function F return T'Class;
>> end Q;
>>
>> in the DLL being loaded, then in the process of elaboration S will be 
>> created which in particular means extending of the dispatching table. 
>> You can return a class-wide object from there and dispatch on the 
>> newly created type's operation.
>>
>> Clear?
> 
> Interesting, better than the shape examples but I guess you have to get 
> that in the first instance.

Dynamic polymorphism is an extremely powerful mechanism, but it kind of 
bends out of traditional typing.

It is like the relativity theory. Everything is relative, position, 
velocity, but up to the point. Acceleration is not anymore. Same is with 
typing: value->type, so far so good, but one more step up: 
value->type->class and something happens. Primitive operations become 
reachable even if you do not see them, you cannot hide them. Multiple 
inheritance, OK, but what about conflicts, is it additive or idempotent? 
Multiple dispatch is a total dark hole.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de