C++: Validate input: Ensure input is int?

Dave!

Hey folks,

I'm doing a little project at the moment and I'm trying to figure out what's the best method to validate the input.

The program prompts the user for an int (for a few functions actually), and I want to ensure that an int -- and only an int -- is accepted.

I've been browsing around looking for ideas, and this is my current attempt:

int number, m;
bool o;
	do {
		cout << "Please enter an integer:";
		cin >> m;
		if(cin >> m && isdigit(m)) {
			number = m;
			o = 1;
			break;
		} else {
			o = 0;
		}
	} while(o == 0);

But it keeps looping through and printing 'please enter.....' if I enter a non-int.

Any ideas? All the methods I've seen are a bit messy, so anything a bit neater would be great!

ps. 3rd year comp sci student, but 1st year doing C++, so go easy!

EL_Loco

try putting a cout statement in each section of the IF and ELSE
and see if it's triggering them correctly based on your input.

sorry I can't be of specific C++ assistance it's been too long.

marco_polo

Just scanned the code but it looks to me to be the expected behaviour of the code as written, unless I'm missing something.

If you enter a non-int then isdigit(m) will evaluate to false as a result the whole if clause will evaluate to false, o will be assigned to zero in the else section, and the do while loop will execute again as long as o is 0.

Dave!

Cheers lads

I actually found an acceptable solution

	int i = 0;
	cout << "Enter int: ";
	while (!(cin >> i)) {
		cin.clear();
		cin.ignore(1000,'\n');
		cout << "Enter an integer value, dipsh*t!";
	}
		other_int = i;

Finally finished this bloody thing I think!!!