Object-oriented Software in Ada 95

Exceptions 207
The implementation of this inherited class is:
package body Class_Better_Stack is
procedure Push( The:in out Better_Stack; Item:in T ) is
D : Natural;
begin
Class_Stack_T.Push( Class_Stack_T.Stack(The), Item );
D := Class_Stack_T_Additions.Items(Class_Stack_T.Stack(The) );
if D > The.Depth then
The.Depth := The.Depth + 1;
end if;
end Push;
function Max_Depth( The:in Better_Stack ) return Natural is
begin
return The.Depth;
end Max_Depth;
end Class_Better_Stack;
14.8.1 Putting it all together
An instantiation of the class Better_stack for Positive numbers is created with the declaration:
with Class_Better_Stack;
pragma Elaborate_All( Class_Better_Stack );
package Class_Better_Stack_Pos is
new Class_Better_Stack(Positive,10);
This is then used in a small test program of the new class as follows:
with Ada.Text_Io, Ada.Integer_Text_Io, Class_Better_Stack_Pos;
use Ada.Text_Io, Ada.Integer_Text_Io, Class_Better_Stack_Pos;
procedure Main is
Numbers : Better_Stack;
Res : Positive;
begin
Put("Max depth "); Put( Max_Depth( Numbers ) ); New_Line;
Push( Numbers, 10 );
Push( Numbers, 20 );
Put("Max depth "); Put( Max_Depth( Numbers ) ); New_Line;
Push( Numbers, 20 );
Put("Max depth "); Put( Max_Depth( Numbers ) ); New_Line;
Pop( Numbers, Res );
Put("Max depth "); Put( Max_Depth( Numbers ) ); New_Line;
null;
end Main;
which when run produces the following results:
Max depth 0
Max depth 2
Max depth 3
Max depth 3
© M A Smith - May not be reproduced without permission