do.. while loops

**kbpsu** · 03-17-2009

i figured out how to incorporate the switch statements into this program, but i am having trouble making the error term come up if the user tries to divide by zero.

Code:

#include <iostream>
using namespace std;
int main()
{
	double n=0, n2=0;
	char operation;

	cout << "Current Total is " << n << endl;

	do
	{
		cout << "Enter an operation: + - * / (or enter X to exit):" << endl;
		cin >> operation;
		if (operation == 'X')
			break;
		cout << "Enter a number: " << endl;
		cin >> n2;
		switch (operation)
		{
			case '+':
				n += n2;
				break;
			case '-':
				n -= n2;
				break;
			case '*':
				n *= n2;
				break;
		/*	case (('/') && (n2==0)):		
				cout << "Can not divide by zero!" << endl;
				break;	
               */	
			case '/':
				n /= n2;
				break;
		}
		cout << "Current Total is " << n << endl;
	} while (operation != 'X');

}

the part that is blocked off by the /* and */ is the part i dont know how to figure out. everything else works well with the program, but i dont know how to combine those two like an if statement would be able to do.

thanks for any help.

**laserlight** · 03-17-2009

Like this:

Code:

switch (operation)
{
case '+':
    n += n2;
    break;
case '-':
    n -= n2;
    break;
case '*':
    n *= n2;
    break;
case '/':
    if (n2 == 0)
    {
        cout << "Can not divide by zero!" << endl;
    }
    else
    {
        n /= n2;
    }
    break;
}

You could have done something like this for your if-else chain version too. It is good practice to check for equality of floating point numbers by checking a range.

**kbpsu** · 03-17-2009

thanks for the quick response. and for being very helpful.

**brewbuck** · 03-17-2009

Originally Posted by laserlight

You could have done something like this for your if-else chain version too. It is good practice to check for equality of floating point numbers by checking a range.

But in this case, the check should be exactly for zero, because you do not divide by zero unless you divide by zero

If the value is non-zero the division should be allowed.

**laserlight** · 03-17-2009

Originally Posted by brewbuck

But in this case, the check should be exactly for zero, because you do not divide by zero unless you divide by zero

I agree, but ask vart to explain otherwise:

Originally Posted by vart

also using == on doubles is not recomended...

Possibility of overflow in this case? I am not sure.

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