Robert Fischer a écrit :
>
>> You don't invent them, they exist. I can't agree to dismiss this 
>> suggestion without further thought. It might end up being 
>> non-sensical, maybe not. It merely suggests a way, to derive new 
>> values, whose type happen to be a supertype of the original one. Why 
>> not ? It may be considered to the Haskell-like "derive" feature, and 
>> such. It is just a way to build new values out of known one.
>>
> Formally, can you explain what you're looking for here, and how it's 
> not congruent with inheritance?
>
> ~~ Robert.
Nope. Absolutely not :p . I wouldn't have a clue of what it should 
formally look like, since again I can't find any example of mathematical 
reasoning using that, I have no intuition at all. But it's not 
impossible that there is a good way to make/read such a feature, that's 
just what I am stating.


Arnaud Spiwack