package body Stack_14
  with SPARK_Mode,
       Refined_State => (S_State       => S,
                         Pointer_State => Pointer)
is
   Stack_Size : constant := 100;
   type    Pointer_Range is range 0 .. Stack_Size;
   subtype Index_Range   is Pointer_Range range 1..Stack_Size;
   type    Vector        is array(Index_Range) of Integer;

   S : Vector;
   Pointer : Pointer_Range;

   procedure Push (X : in Integer)
     with Refined_Global => (In_Out => (S, Pointer))
   is
   begin
      Pointer := Pointer + 1;
      S (Pointer) := X;
   end Push;

   procedure Pop(X : out Integer)
     with Refined_Global => (Input  => S,
                             In_Out => Pointer)
   is
   begin
      X := S (Pointer);
      Pointer := Pointer - 1;
   end Pop;
begin
   -- initialization
   Pointer := 0;
   S := Vector'(Index_Range => 0);
end Stack_14;
