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Date: Thu, 1 Sep 2022 11:54:00 -0700 (PDT)
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Subject: Re: Calling inherited primitive operations in Ada
From: Emmanuel Briot <briot.emmanuel@gmail.com>
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I think I have a more interesting example. This one is extracted from my at=
tempted traits containers, for which I had published a blog post at AdaCore=
. My enhanced fork of the library is at=20
 https://github.com/briot/ada-traits-containers
if someone wants to experiment with non-trivial generics code (and containe=
rs are of course a case where generics fully make sense).

Here is the example:

generic
   type Element_Type is private;
   type Stored_Type is private;
package Elements is
end Elements;

with Elements;
generic
   type Element_Type is private;
package Definite_Elements is
   package Traits is new Elements (Element_Type, Stored_Type =3D> Element_T=
ype);
end Definite_Elements;

with Definite_Elements;
generic
   type Key_Type is private;
package Maps is
   package Keys is new Definite_Elements (Key_Type);
   function "=3D" (L, R : Keys.Traits.Stored_Type) return Boolean   --   "S=
tored_Type" is not a visible entity of "Traits"
      is (False);
end Maps;


This is not case where the actual is visible unless I happen to know how De=
finite_Element is implemented and that it will use Element_Type for Stored_=
Type (and this is not a knowledge I wish client packages to have, the whole=
 point of Element and Definite_Element is to basically hide how elements ca=
n be stored in a container, and whether we need memory allocation for insta=
nce).