Object-oriented Software in Ada 95

Ada introduction: Part 2 41
4.4 Modified countdown program
The countdown program shown earlier in Section 3.4 can be rewritten, restricting count to the values 1 to 10 as
follows:
with Ada.Text_Io;
use Ada.Text_Io;
procedure Main is
type Count_Range is range 0 .. 10;
Count : Count_Range := 10; --Declaration of count
begin
for Count in reverse Count_Range loop
if Count = 3 then --If 3 print Ignition
Put("Ignition"); New_Line;
end if;
Put( Count_Range'Image( Count ) ); --Print current count
New_Line;
Delay 1.0;
-- Wait 1 second
end loop;
Put("Blast off"); New_Line; --Print Blast off
end Main;
Note: Even though count is of type Count_range, it can be compared with the integer constant 3.
The use of the type Count_Range in the loop statement. This confines the loop to the range of
values that an instance of Count_Range can take.
The use of
Count_Range'Image( Count )
to deliver a character representation of the contents of count. Remember count is of type
Count_Range.
4.5 Input and output in Ada
One of the obstacles in writing programs in Ada is the complexity involved in outputting integer and floating
point numbers. To simplify this process Ada 95 provides the following packages:
• Ada.Integer_Text_Io for input and output of integer numbers.
• Ada.Float_Text_Io for input and output of floating point numbers.
• Ada.Text_Io for input and output of characters and strings.
Chapter 18 describes how specific packages in Ada.Text_Io are instantiated to output instances of other integer
and floating point types.
4.6 The package Ada.Float_Text_Io
The package Ada.Float_Text_Io is used to input and output floating point numbers.
© M A Smith - May not be reproduced without permission