Integer validation for input

Question

I tried to prompt user for input and do the validation. For example, my program must take in 3 user inputs. Once it hits non-integer, it will print error message and prompt

Answer 1

The problem is in the while condition

bool valid = true;
while(valid){

You loop until you get a non valid input, this absolutly not what you want! loop condition should be like this

bool valid = false;
while(! valid){ // repeat as long as the input is not valid

Here is a modified version of your read_double

double read_input()
{
    double input;
    bool valid = false;
    while(! valid){ // repeat as long as the input is not valid
        cout << "Enter number: " ;
        cin >> input;
        if(cin.fail())
        {
            cout << "Wrong input" << endl;

            // clear error flags
            cin.clear(); 
            // Wrong input remains on the stream, so you need to get rid of it
            cin.ignore(INT_MAX, '\n');
        }
        else 
        {
            valid = true;
        }
    }
    return input;
}

And in your main you need to ask for as may doubles as you want, for example

int main()
{
    double d1 = read_input();
    double d2 = read_input();
    double d3 = read_input();

    cout << "Numbers entered are: " << d1 << ", " << d2 << ", " << d3 << endl;

    return 0;
}

You may also want to have a loop where you call read_double() and save the returned values in an array.