ReadAndValidateTemplate.cpp

template<class T>
T ReadAndValidate() {
    T n;
    cout << "enter number:";
    cout.flush();
    cin >> n;

    while (cin.fail() == 1 || n < 0) {
        cin.clear();
        cin.ignore(1000, '\n'); //throw away 1000 chars, or next end of line
        cout << "\nincorrect value, enter another:";
        cin >> n;
    }

    cout << "\n entered: " << n << endl;
}

Reads in a single value and does not allow user to enter incorrect values, prompts indefinitely until valid input has been registered.