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-- CC54003.A

--

--                             Grant of Unlimited Rights

--

--     Under contracts F33600-87-D-0337, F33600-84-D-0280, MDA903-79-C-0687,

--     F08630-91-C-0015, and DCA100-97-D-0025, the U.S. Government obtained

--     unlimited rights in the software and documentation contained herein.

--     Unlimited rights are defined in DFAR 252.227-7013(a)(19).  By making

--     this public release, the Government intends to confer upon all

--     recipients unlimited rights  equal to those held by the Government.

--     These rights include rights to use, duplicate, release or disclose the

--     released technical data and computer software in whole or in part, in

--     any manner and for any purpose whatsoever, and to have or permit others

--     to do so.

--

--                                    DISCLAIMER

--

--     ALL MATERIALS OR INFORMATION HEREIN RELEASED, MADE AVAILABLE OR

--     DISCLOSED ARE AS IS.  THE GOVERNMENT MAKES NO EXPRESS OR IMPLIED

--     WARRANTY AS TO ANY MATTER WHATSOEVER, INCLUDING THE CONDITIONS OF THE

--     SOFTWARE, DOCUMENTATION OR OTHER INFORMATION RELEASED, MADE AVAILABLE

--     OR DISCLOSED, OR THE OWNERSHIP, MERCHANTABILITY, OR FITNESS FOR A

--     PARTICULAR PURPOSE OF SAID MATERIAL.

--*

--

-- OBJECTIVE:

--      Check that a general access-to-subprogram type may be passed as an

--      actual to a generic formal access-to-subprogram type. Check that

--      designated subprograms may be called by dereferencing the access

--      values.

--

-- TEST DESCRIPTION:

--      The generic implements a stack of access-to-subprogram objects as an

--      array. The profile of the access-to-subprogram formal corresponds to

--      a function which accepts a parameter of some type and returns an

--      object of the same type.

--

--      For this test, the functions for which access values will be pushed

--      onto the stack accept a parameter of type access-to-string, lengthen

--      the pointed-to string, then return an access object pointing to this

--      lengthened string.

--

--      The instance declares a function Execute_Stack which executes each

--      subprogram on the stack in sequence. This function accepts some initial

--      access-to-string, then returns an access object pointing to the

--      lengthened string resulting from the execution of the stacked

--      subprograms. Access-to-string objects are used rather than strings

--      themselves because the initial string "grows" during each iteration.

--

--

-- CHANGE HISTORY:

--      06 Dec 94   SAIC    ACVC 2.0

--      10 Apr 96   SAIC    ACVC 2.1: Added pragma Elaborate to context clause

--                          preceding CC54003_2.

--

--!

generic

   Size : in Positive;

   type Item_Type (<>) is private;

   type Item_Ptr is access Item_Type;

   type Function_Ptr is access function (Item : Item_Ptr)

     return Item_Ptr;

package CC54003_0 is -- Generic stack of pointers.

   type Stack_Type is private;

   procedure Push (Stack    : in out Stack_Type;

                   Func_Ptr : in     Function_Ptr);

   function Execute_Stack (Stack         : Stack_Type;

                           Initial_Input : Item_Ptr) return Item_Ptr;

   -- ... Other operations.

private

   subtype Index is Positive range 1 .. (Size + 1);

   type Stack_Type is array (Index) of Function_Ptr;       -- Last slot unused.

   Top : Index := 1;                  -- Top refers to the next available slot.

end CC54003_0;

     --===================================================================--

package body CC54003_0 is

   procedure Push (Stack    : in out Stack_Type;

                   Func_Ptr : in     Function_Ptr) is

   begin

      Stack(Top) := Func_Ptr;

      Top := Top + 1;     -- Artificial: no Constraint_Error protection.

   end Push;

   -- Call each subprogram on the stack in sequence. For the first call, pass

   -- Initial_Input. For succeeding calls, pass the result of the previous

   -- call.

   function Execute_Stack (Stack         : Stack_Type;

                           Initial_Input : Item_Ptr) return Item_Ptr is

      Result : Item_Ptr := Initial_Input;

   begin

      for I in reverse Index'First .. (Top - 1) loop    -- Artificial: no C_E

         Result := Stack(I)(Result);                    -- protection.

      end loop;

      return Result;

   end Execute_Stack;

end CC54003_0;

     --===================================================================--

package CC54003_1 is

   subtype Message     is String;

   type    Message_Ptr is access Message;

   function Add_Prefix (Msg_Ptr : Message_Ptr) return Message_Ptr;

   function Add_Suffix (Msg_Ptr : Message_Ptr) return Message_Ptr;

   -- ...Other operations.

end CC54003_1;

     --===================================================================--

package body CC54003_1 is

   function Add_Prefix (Msg_Ptr : Message_Ptr) return Message_Ptr is

      Sender  : constant String := "Dummy: ";    -- Artificial; in a real

                                                 -- application Sender might

      New_Msg : Message := Sender & Msg_Ptr.all; -- be a call to a function.

   begin

      return new Message'(New_Msg);

   end Add_Prefix;

   function Add_Suffix (Msg_Ptr : Message_Ptr) return Message_Ptr is

      Time : constant String := " (12:03pm)";    -- Artificial; in a real

                                                 -- application Time might be a

      New_Msg : Message := Msg_Ptr.all & Time;   -- be a call to a function.

   begin

      return new Message'(New_Msg);

   end Add_Suffix;

end CC54003_1;

     --===================================================================--

with CC54003_0;      -- Generic stack of pointers.

pragma Elaborate (CC54003_0);

with CC54003_1;      -- Message abstraction.

package CC54003_2 is

   type Operation_Ptr is access function (Msg_Ptr : CC54003_1.Message_Ptr)

     return CC54003_1.Message_Ptr;

   Maximum_Ops : constant := 4;         -- Arbitrary.

   package Stack_of_Ops is new CC54003_0

     (Item_Type    => CC54003_1.Message,

      Item_Ptr     => CC54003_1.Message_Ptr,

      Function_Ptr => Operation_Ptr,

      Size         => Maximum_Ops);

   Operation_Stack : Stack_Of_Ops.Stack_Type;

   procedure Create_Operation_Stack;

end CC54003_2;

     --===================================================================--

package body CC54003_2 is

   procedure Create_Operation_Stack is

   begin

      Stack_Of_Ops.Push (Operation_Stack, CC54003_1.Add_Prefix'Access);

      Stack_Of_Ops.Push (Operation_Stack, CC54003_1.Add_Suffix'Access);

   end Create_Operation_Stack;

end CC54003_2;

     --===================================================================--

with CC54003_1;  -- Message abstraction.

with CC54003_2;  -- Message-operation stack.

with Report;

procedure CC54003 is

   package Msg_Ops renames CC54003_2.Stack_Of_Ops;

   Msg      : CC54003_1.Message_Ptr := new CC54003_1.Message'("Hello there");

   Expected : CC54003_1.Message     := "Dummy: Hello there (12:03pm)";

begin

   Report.Test ("CC54003", "Check that a general access-to-subprogram type " &

                           "may be passed as an actual to a generic formal " &

                           "access-to-subprogram type");

   CC54003_2.Create_Operation_Stack;

   declare

      Actual : CC54003_1.Message_Ptr :=

        Msg_Ops.Execute_Stack (CC54003_2.Operation_Stack, Msg);

   begin

      if Actual.all /= Expected then

         Report.Failed ("Wrong result from dereferenced subprogram execution");

      end if;

   end;

   Report.Result;

end CC54003;