47
generic
  type Element_Type is private;
  with function Hash
    (Element : Element_Type) return Hash_Type;
  with function Equivalent_Elements
    (Left, Right : Element_Type) return Boolean;
  with function "=" (Left, Right : Element_Type)
     return Boolean is <>;
  -- ET."=" only used for Set."="; see p.74.
package Ada.Containers.Hashed_Sets is ...;