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Newsgroups: comp.lang.ada
Subject: Re: Help needed for ada package
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From: Ludovic Brenta <ludovic.brenta@tiscali.be>
Date: Thu, 28 Jul 2005 20:33:32 +0200
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Date: 2005-07-28T20:33:32+02:00
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Whoa, everyone seems to be going over the top, I think the solution
can be much simpler.

generic
    type ID is (<>); --some discrete type to be put here
package POP is
   --update database
  type Rating is new Integer range 0..255;
  procedure Rate (Citizen : in ID;
                  Badness : in Rating);
  procedure Associate (Citizen_1, Citizen_2 : in ID);
  --query the database
  function Most_Dangerous return ID;
  function Next_Member return ID;
  function More_In_Group return Boolean;
  --administrative
  procedure reset;
end POP;


Since the type ID is discrete, why not just use that as the array index type?

package body POP is
   Society : array (ID) of Rating := (others => Rating'First);
   Associacion : array (ID, ID) of Boolean := (others => others => False));
   pragma Pack (Association);

   Last_Reported : ID := ID'First;

   procedure Rate (Citizen : in ID;
                   Badness : in Rating) is
   begin
      Society (Citizen) := Rating;
   end Rate;

   procedure Associate (Citizen_1, Citizen_2 : in ID) is
   begin
      Association (Citizen_1, Citizen_2) := True;
   end Associate;

   function Most_Dagerous return ID is
      Result : ID := ID'First;
   begin
      for J in Society'Range loop
         if Society (J) > Result then
            Result := J;
         end if;
      end loop;
      return Result;
   end Most_Dangerous;


   function Next_Member return ID is
      J : constant ID := Most_Dangerous;
   begin
      if Last_Reported = ID'First then
         Last_Reported := J;
      end if;
      for K in ID'Succ (Last_Reported) .. Association'Last (2) loop
         if Association (J, K) then
            Last_Reported := K;
            exit;
         end loop;
      end loop;
      return Last_Reported;
   end Next_Member;


   function More_In_Group return Boolean is    
      J : constant ID := Most_Dangerous;
      Result : Boolean := False;
   begin
      for K in ID'Succ (Last_Reported) .. Association'Last (2) loop
         if Association (J, K) then
            Result := True;
            exit;
         end loop;
      end loop;
      return Result;
   end More_In_Group;


   procedure Reset is
   begin
      Society := (others => Rating'First);
      Association := (others => others => False));
      Last_Reported := ID'First;
   end Reset;
end POP;


Of course, the above solution is outrageously inefficient, both
memory- and CPU-wise.  Optimisations are left as an exercise to the
reader.

-- 
Ludovic Brenta.