Object-oriented Software in Ada 95

Procedures and functions 69
5.8 Different number of parameters
As the compiler can distinguish between overloaded names, several functions that deliver the maximum or larger
of their parameters can be written. With re-use in mind the first function Max2 can be written which delivers the
maximum of the two Integer parameters passed to it.
function Max2( A,B:in Integer ) return Integer is
begin
if A > B then
return A; --a is larger
else
return B;
end if;
end Max2;
--b is larger
This function Max2 can be re-used in a function Max3 that will deliver the larger of three parameters passed to it.
with Max2;
function Max3( A,B,C:in Integer ) return Integer is
begin
return Max2( Max2( A,B ), C );
end Max3;
Then the following code can be written:
with Ada.Text_io, Ada.Integer_Text_Io, Max2, Max3;
use Ada.Text_io, Ada.Integer_Text_Io;
procedure Main is
function Max(A,B:in Integer) return Integer renames Max2;
function Max(A,B,C:in Integer) return Integer renames Max3;
begin
Put("Larger of 2 and 3 is "); Put( Max(2,3) ); New_Line;
Put("Larger of 2 3 4 is "); Put( Max(2,3,4) ); New_Line;
end Main;
Note:
The use of renames to overload the name Max with 2 distinct function definitions.
which when run produces:
Larger of 2 and 3 is 3
Larger of 2 3 4 is 4
Note:
The overloading of names in an Ada program can provide a simpler interface for a programmer.
However, the overuse of overloading can lead to programs that are difficult to maintain and debug.
5.9 Default values and named parameters
If a default value is given to a parameter, then it may be omitted by a programmer when they write the call to the
function or procedure.
For example, the function sum whose four parameters have a default value of zero returns the sum of these
parameters. The procedure Answer_Is prints the first parameter with an additional message when the second
parameter has the default value True.
© M A Smith - May not be reproduced without permission