Object-oriented Software in Ada 95

200 Child libraries
14.4.1 Example of the use of the generic procedure G_3Order
A program to order the height of three people is shown below. In this program, a record of type Person is
created for each of the individuals. A specific instance of the generic procedure G_3Order is created to order
these records into ascending height order.
with Ada.Text_Io, G_3Order;
use Ada.Text_Io;
procedure Main is
Max_Chs : constant := 7;
type Gender is ( Female, Male );
type Height_Cm is range 0 .. 300;
type Person is record
Name : String( 1 .. Max_Chs ); --Name as a String
Height : Height_Cm := 0; --Height in cm.
Sex : Gender; --Gender of person
end record;
function Gt( First,Second:in Person ) return Boolean is
begin
return First.Height > Second.Height;
end Gt;
procedure Order is new G_3Order( Person, Gt ); --Instantiate
Person1 : Person := ("Corinna", 171, Female );
Person2 : Person := ("Miranda", 74, Female );
Person3 : Person := ("Mike ", 183, Male );
begin
Order( Person1, Person2, Person3 );
Put("List of people in ascending height order are"); New_Line;
Put( Person1.Name ); New_Line;
Put( Person2.Name ); New_Line;
Put( Person3.Name ); New_Line;
end Main4;
which when run would print:
List of people in ascending height order are
Miranda
Corinna
Mike
14.4.2 Summary
The following table summarizes the effect of different subprogram specifications for a formal parameter.
Generic formal subprogram
with function ">" ( a, b:in T )
return Boolean is ;
with function ">" ( a, b:in T )
return Boolean;
with procedure exec is exec;
Explanation
Has a default value of the current
definition of ">" at the point of
instantiation of the generic subprogram.
Takes the value of the formal parameter
">" at the point of instantiation of the
generic subprogram.
Takes the value of the formal parameter
at the point of definition of the generic
subprogram.
© M A Smith - May not be reproduced without permission