Object-oriented Software in Ada 95

70 Procedures and functions
function Sum( P1:in Integer := 0;
P2:in Integer := 0;
P3:in Integer := 0;
P4:in Integer := 0 ) return Integer is
begin
return P1 + P2 + P3 + P4;
end Sum;
with Ada.Text_Io, Ada.Integer_Text_io;
use Ada.Text_Io, Ada.Integer_Text_io;
procedure Answer_Is( N:in Integer;
Message:in Boolean := True ) is
begin
if Message then Put("The answer = "); end if;
Put( N, Width=>1 );
if Message then New_Line; end if;
end Answer_Is;
Note: Formal parameters to the function Sum are given a default value of 0, if a value has not been supplied
by a caller of the function.
Any actual parameter to a function or procedure may be specified either by position or by name. For example, the
second formal parameter to the function Answer_Is can be specified in the following ways:
Answer_Is( 27, True ); -- By position
Answer_Is( 27, Message => False ); -- By name
Note:
If a parameter is specified by name, then all subsequent parameters must be specified by name.
5.9.1 Putting it all together
The procedures sum and Answer_Is can be used in a program as follows:
with Sum, Answer_Is;
procedure Main is
begin
Answer_Is( Sum );
Answer_Is( Sum( 1, 2 ) );
Answer_Is( Sum( 1, 2, 3 ) );
Answer_Is( Sum( 1, 2, 3, 4 ), Message => False );
New_Line;
end Main;
The code that is actually compiled for the procedure Main above is:
with Sum, Answer_Is;
procedure Main is
begin
Answer_Is( Sum( 0, 0, 0, 0 ), True );
Answer_Is( Sum( 1, 2, 0, 0 ), True );
Answer_Is( Sum( 1, 2, 3, 0 ), True );
Answer_Is( Sum( 1, 2, 3, 4 ), False );
New_Line;
end Main;
which is more complex for the writer to construct and for a maintainer to follow.
© M A Smith - May not be reproduced without permission