Re: Ada Containers

[Simon Wright <simon@pushface.org>]

rwilco19@gmail.com writes:

> Can someone please explain to me the difference between
> Ada.Containers.Hashed_Tables and Ada.Containers.Hashed_Maps, and when
> you might want to use a Hashed_Table over a Hashed_Map?

Ada.Containers.Hash_Tables, as you noted.

Hashed_Maps is in the Standard, Hash_Tables is not; it's part of
AdaCore's implementation (and maybe others, for all I know).

GCC 4.7.0 says for Hashed_Maps

   with Ada.Iterator_Interfaces;

   private with Ada.Containers.Hash_Tables;
   private with Ada.Finalization;
   private with Ada.Streams;

   generic
      type Key_Type is private;
      type Element_Type is private;

      with function Hash (Key : Key_Type) return Hash_Type;
      with function Equivalent_Keys (Left, Right : Key_Type) return Boolean;
      with function "=" (Left, Right : Element_Type) return Boolean is <>;

   package Ada.Containers.Hashed_Maps is

and you will see that Hash_Tables is withed privately (i.e., it's only
used in the private part, "not specified by the language").

A further clue: the comment at the start of Hash_Tables says "This
package declares the hash-table type used to implement hashed
containers."