accesstypes.adb

Ada 2005 Training Notes.

package body AccessTypes is

procedure Init is
   Cell : Game_Cell := Abyss;
   begin

      for Neighbor_Idx in Cell.Neighbor_Count'Range loop

         Cell.Total_Neighbor_Count :=
           Cell.Total_Neighbor_Count +
             Cell.Neighbor_Count(Neighbor_Idx).all;
      end loop;

      Live_Access.Life_Count := 1;

      -- ACT access to constant type
      -- can access to different objects of the defined type
      -- but cannot change them
      --
      ACT := NWCell'Access;

      --
      -- CAT can only access to object its initialized with.
      CAT.Life_Count := 1;	-- Can access the object it's initialized with
      -- Cannot access the objects other then its initialized with
      -- ERROR : left hand side of assignment must be a variable
      -- CAT := NWCell'Access;


   end Init;

function MyProc(CATP: access constant Game_Cell; ACTP: access constant Game_Cell)
                return not null Game_Cell_Ptr is
      R: Game_Cell_Ptr;
   begin
      R := new Game_Cell'(Abyss);
      R.Total_Neighbor_Count := CATP.Total_Neighbor_Count;
      return R;
   end MyProc;

   procedure AccessNotAllowed is
      type AI is access all Integer;
      Ref1: AI;
   begin
      declare
         Ref2: AI;
         I: aliased Integer;
      begin
         -- Assignment not allowe because using Ref1 := Ref2
         -- would refer to I out of it's life.
         -- Ref2 := I'Access;
         -- Ref1 := Ref2;
         I := 1;
      end;
   end AccessNotAllowed;


--
--   function CannotAddToList(The_List: access Game_Cell;
--                            Obj_Ptr: access Game_Cell) return access Game_Cell is
--      Local: access Game_Cell := new Game_Cell;
--   begin
--      Local.Next := The_List;
--      return Local;
--   end CannotAddToList;
--

   function AddToList(The_List: access Game_Cell;
                      Obj_Ptr: access constant Game_Cell) return access Game_Cell is
   begin
      return Local: access Game_Cell := new Game_Cell do
         Local.Next := The_List;
      end return;
   end AddToList;

   --
   -- ERROR: functions can only have "in" parameters
   --
   -- function InOutParameter(PIO: in out Game_Cell) return Game_Cell is
   -- begin
   --   return PIO;
   -- end InOutParameter;


end AccessTypes;