Re: why "unconstrained subtype in component declaration" while said component given default value ?

[Mehdi Saada <00120260a@gmail.com>]

>   type Unconstrained_Collection
>     (Maximum_Size : Positive) is new Abstract_Collection with private;

>   subtype Collection
>      is Unconstrained_Collection (Maximum_Size => Maximum_Size);

It's close, but I would like to hide publicly the discriminants. I would like:
one unconstrained subtype with (<>) which needs initialization, and one subtype who doesn't need it. In fact, I don't need necessarily subtypes:
I could have:
type A(<>) is private;
type B is private;
private
  type A( - discriminants with or without defaults -) is ...
  subtype B is A ( some values); -- not possible, I already complained about it.

I can already get what I want if B is made a derived type of A. No need for tagged types here.