Size : Positive;
type Item is private;
package Stack is
procedure Push(E : in Item);
procedure Pop (E : out Item);
Overflow, Underflow : exception;
end Stack;
Space : Table(1 .. Size);
Index : Natural := 0;
begin
if Index >= Size then
raise Overflow;
end if;
Index := Index + 1;
Space(Index) := E;
end Push;
begin
if Index = 0 then
raise Underflow;
end if;
E := Space(Index);
Index := Index - 1;
end Pop;
package Stack_Bool is new Stack(100, Boolean);
Stack_Bool.Push(True);
type Item is private;
package On_Stacks is
type Stack(Size : Positive) is limited private;
procedure Push(S : in out Stack; E : in Item);
procedure Pop (S : in out Stack; E : out Item);
Overflow, Underflow : exception;
private
type Table is array (Positive range <>) of Item;
type Stack(Size : Positive) is
record
Space : Table(1 .. Size);
Index : Natural := 0;
end record;
end On_Stacks;
package Stack_Real is new On_Stacks(Real); use Stack_Real;
S : Stack(100);
begin
...
Push(S, 2.54);
...
end;