Infinite Loop in C++ function

Question

I have written a very little program that adds two integers:

#include <iostream>
using namespace std;

int inpInt() {            //ask for an input in integer format
    int number = 0;
    cin >> number;       
    while (!cin) {        //keep asking if the input was not an integer
        cin >> number;
    }
    return number;
}

int main() {
    int summand1, summand2, sum;
    cout << "Summand 1: "; summand1 = inpInt();
    cout << "Summand 2: "; summand2 = inpInt();
    sum = summand1 + summand2;
    cout << "Sum: " << sum << "\n";
}

The problem is that when I do not enter an integer, I am trapped in an infinite loop where I cannot enter neither an integer nor anything else. The strange thing is that when I include the integer testing loop in main(), the code works.

Thank you very much for any help!

Answer 1

You have to explicitly clear cin and ignore newlines (newline appears when you hit return)

int inpInt() {            //ask for an input in integer format
    int number = 0;
    while (!(cin >> number)) {
        cin.clear(); // clear cin
        cin.ignore(numeric_limits<streamsize>::max(), '\n'); // ignore new lines. see: http://www.cplusplus.com/reference/istream/istream/ignore/
    }
    return number;
}

int main() {
    int summand1, summand2, sum;
    cout << "Summand 1: "; summand1 = inpInt();
    cout << "Summand 2: "; summand2 = inpInt();
    sum = summand1 + summand2;
    cout << "Sum: " << sum << "\n";
}