Ada Containers

Ada Containers

[rwilco19]

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?

Re: Ada Containers

[Maciej Sobczak]

W dniu niedziela, 7 października 2012 21:58:41 UTC+2 użytkownik rwil...@gmail.com napisał:

> Can someone please explain to me the difference between Ada.Containers.Hashed_Tables and Ada.Containers.Hashed_Maps,

Yes, it is very easy - Hashed_Tables does not exists at all, whereas Hashed_Maps is a pretty useful package. :-)

Did you perhaps meant some other package? Which one?

-- 
Maciej Sobczak * http://www.msobczak.com * http://www.inspirel.com

Re: Ada Containers

[rwilco19]

Do you mean doesn't exist, or cannot be used?

Here's a reference page for it:
http://www.martin.dowie.btinternet.co.uk/Containers/adabrowse/ada-containers-hash_tables.html

This page shows it in the dependency list for Hashed_Maps
http://www.martin.dowie.btinternet.co.uk/Containers/adabrowse/ada-containers-hashed_maps.html

"with Ada.Containers.Hash_Tables;"

Re: Ada Containers

[Martin]

I should probably pull these pages down...that's 8 years old now and "real" versions are available.

-- Martin

Re: Ada Containers

[georg bauhaus]

Martin <martin@thedowies.com> wrote:
> I should probably pull these pages down...that's 8 years old now and
> "real" versions are available.

They are good to have if you still
run nice Ada 95 compilers.

Re: Ada Containers

[rwilco19]

Maby I caused some confusion earlier with a type. I misspelled the package name. It's Ada.Containers.Hash_Tables not Ada.Containers.Hashed_Tables.

Re: Ada Containers

[Georg Bauhaus]

On 07.10.12 23:30, rwilco19@gmail.com wrote:
> Maby I caused some confusion earlier with a type. I misspelled the package name. It's Ada.Containers.Hash_Tables not Ada.Containers.Hashed_Tables.
>

In GNAT, package Ada.Containers.Hash_Tables
"declares the hash-table type used to implement hashed containers."

In Ada, the hashed containers are Ada.Containers.Hashed_Maps
and Ada.Containers.Hashed_Sets, and variants like Bounded_*
(new in Ada 2012) and Indefinite_*. So Hash_Tables is part of
GNAT's implementation of Ada's hashed containers, perhaps for
use by implementers only.

(You can see in the sources of GNAT's implementation of
Ada's library, this context clause in Ada.Containers.Hashed_Maps:

(private with Ada.Containers.Hash_Tables;)

Re: Ada Containers

[Simon Wright]

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."