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Next: Example Program: Area and
Up: The if-else Statement
Previous: Example Program: Wages Calculation
In exercise 7 of Lesson 7 it was
required to write a program to input two integer values 
and 
,
where 
and to output the corresponding Pythagorean triple 
, 
and 
. This is now extended so that the values
of and entered by the user are validated to ensure
that is greater than . A suitable algorithmic description is:
enter values for m and n.
if m is greater than m
then
{
calculate the pythagorean numbers
from m and n.
output the pythagorean numbers.
}
otherwise output a warning message.
This algorithmic description is now easily converted into the following C++ program:
// IEA 1996
// Program to produce pythagorean triples
// with input validation.
#include <iostream.h>
void main()
{
int m, n; // entered by user to generate triple
int t1, t2, t3; // The values of the triple
// input from user
cout << "Input values for m and n, m > n : ";
cin >> m >> n;
// now validate m and n
if (m > n)
{
t1 = m*m-n*n;
t2 = 2*m*n;
t3 = m*m+n*n;
cout << "The triple corresponding to "
<< m << " and " << n << " is "
<< t1 << " " << t2 << " " << t3
<< endl;
}
else
cout << "m must be greater than n!"
<< endl
<< "you entered m as " << m
<< " and n as " << n
<< endl;
}
Download program.
Note that the values of m and n entered by the user are
printed as part of the output. This is good practice. Programs
should not only display results but should give some indication of the
data that produced the results. In this case the input data set was
produced in full since it was small. In situations where the input
data set was large it might not be realistic to reproduce it all but
an indication such as
Results produced from Data Set No 23might be output. This is vital if a listing of results is to mean anything at a future date.