User defined function issue - different answers

[AceSmith]

I have written a code which uses a number of functions but something bizarre happens for one of these functions.

it has two double parameters a and b.

cout<<expression(0,20)<<","; This gives the answer 0.179 - which is what I am expecting

but when i do the following:

  double a, b;
    cout<<"Insert values for a and b:";
    cin>>a>>b;
   cout<<"expression(a,b) = "<<expression(a,b)<<endl;

Here I get the value 1 which is not what I want.

I don't understand why this is happening. Can someone please help.

[Peter87]

Make sure a and b is read successfully.

if (cin >> a >> b)
{
	cout << "expression(a,b) = " <<expression(a, b) << endl;
}
else
{
	cout << "Invalid input!" << endl;
}

[AceSmith]

I still get 1 using this :/

[Peter87]

You enter 0 and 20 as the values for a and b?

Is the return value of expression only depending on the two arguments?

[AceSmith]

yep!

well, expression returns
return sqrt(a*a +b*b) *sum(20000);

sum(20000) is another user defined functions which then relies on another two user defined functions..all of which work perfectly well

[Peter87]

Can you show sum and the two other functions, if you don't mind?

[AceSmith]

I can't Im sorry. But I evaluated all of the functions as above and have realised sum is the problem - it comes up with "nan"

[MikeyBoy]

Just for your own sanity, I'd modify your code to print out the values of a and b, just so you're sure they're correct:

if (cin >> a >> b)
{
	cout << "expression(" << a << "," << b << ") = " <<expression(a, b) << endl;
}
else
{
	cout << "Invalid input!" << endl;
}

Edit: Actually, what I'd really suggest is stepping through your code in a debugger, so that you can see exactly what's going on.