Question

The basic idea of my code is for the user to enter either the spelling of 0-9 i.e. zero, one etc. or the actual numeral and for it to output the numeral/spelling respectively.

I managed to do this with a while loop using while(cin >> number) (number being a string variable) and then use if statements to select the appropriate output option i.e. “zero” –> 0, and “0”–> zero.

At first though I tried to do it as follows;

while (cin >> number || cin >> n) 
{
    if (n == 0)
        cout << digits[0] << endl;
           .
           . 
           .
    else if (n == 9)
        cout << digits[9] << endl;  

    if (number == digits[0])
        cout << 0 << endl;
           .
           .
           .
    else if (number == digits[9])
        cout << 9 << endl;  
}

digits is just a vector class that stores the strings “zero”, “one” etc.

This didn’t work though, when a string was entered the output was correct but when an integer was entered the output was always “zero”. I was wondering why this doesn’t work? I figured its something to do with the while loop conditions. Can’t the computer identify if a string/integer was entered and carry out the appropriate action?

Answer 1

The problem is that cin >> number is always going to succeed since number is a string (as long as you don’t hit EOF or some other failure condition); if the user types in a digit, number is going to hold the number as a string. So cin >> n won’t happen.

You should compare your number against the strings "0".."9" instead (in addition to testing the digit names). You should also use a loop instead of a chain of if/else if.