Re: Ada OO Mechanism

[Matthew Heaney <matthew_heaney@acm.org>]

Hyman Rosen <hymie@prolifics.com> writes:

> So you mean in Ada, I can write a dot(a,b) which will dispatch on
> either a or b?

Yes, if A and B have the same specific type. 

    <types AT and BT derive from T>

    A1, A2 : AT;
    B1, B2 : BT;

    AC1, AC2 : T'Class := <object has type AT>;
    BC1, BC2 : T'Class := <object has type BT>;

  begin
    
   .. := Dot (A, B);    -- illegal, detected at compile-time

         Dot (A1, A2);  -- legal
         Dot (B1, B2);  -- legal

         Dot (AC1, AC2);  -- legal, tags compared at run-time
         Dot (BC1, BC2);  -- legal, tags compared at run-time

         Dot (AC1, BC1);  -- legal, but run-time tag check fails,
                          -- and Constraint_Error is raised
  end;