RE: Usage of Interfaces with Ada 95

["Mário Amado Alves" <amado.alves@netcabo.pt>]

> >   generic
> >      type Iterator_Type is private;
> >      with function Succ (Iterator : Iterator_Type)
> >        return Iterator_Type is <>;
> >      with procedure Process (Iterator : Iterator_Type) is <>;
> >      with function "=" (L, R : Iterator_Type)
> >        return Boolean is <>;
> >   procedure Generic_Algorithm (First, Back : Iterator_Type);
>
> I think the is a different view on the topic by defining a 
> functionality of an interface, providing a generic 
> implementation which defines the 
> interface for the programmer. This was exactly what i dont like to 
> do. I dont like to spent the effort of breaking down a concept into 
> a generic implementation. This is the reason why i like to 
> use interfaces.

Somebody has to implement at some point. I think the example come short.
There is a 'zero-implementation' way to specify interfaces in Ada:
signature packages. The signature package for the stuff above is

generic
  type Iterator_Type is private;
  with function Succ (Iterator : Iterator_Type) return Iterator_Type is
<>;
  with procedure Process (Iterator : Iterator_Type) is <>;
  with function "=" (L, R : Iterator_Type) return Boolean is <>;
  with procedure Generic_Algorithm (First, Back : Iterator_Type) is <>;
package Signature is end;