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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Tally
Date: Wed, 15 Jan 2020 11:52:56 +0000
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Date: 2020-01-15T11:52:56+00:00
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Simon Wright <simon@pushface.org> writes:

> The Booch Components included Bags, which would solve this directly!
> (not that I'd recommend anyone to use the BCs for a new project)

This is what it'd look like (it's a lot uglier in Ada 95, because the
containers and iterators, while tagged, can't use dotted notation).
Sorry about the silly Hash function.

with BC.Containers.Bags.Unmanaged;
with Ada.Text_IO; use Ada.Text_IO;

procedure Main
is
   package Abstract_Containers is new BC.Containers (Natural);
   package Abstract_Bags is new Abstract_Containers.Bags;
   function Hash (N : Natural) return Natural is (N);
   package Bags is new Abstract_Bags.Unmanaged
     (Buckets => 43,
      Hash => Hash);

   type Input_Data is array (Natural range <>) of Natural;

   Input : Input_Data := (2, 3, 8, 2, 2, 2, 7, 2, 3, 4, 8);

   Counts : Bags.Bag;

begin
   for Number of Input loop
      Counts.Add (Number);
   end loop;
   declare
      It : Abstract_Containers.Iterator'Class := Counts.New_Iterator;
   begin
      while not It.Is_Done loop
         Put_Line (It.Current_Item'Image
                     & " -> "
                     & Counts.Count (It.Current_Item)'Image);
         It.Next;
      end loop;
   end;
end Main;