Thread: Input validation loop failure

Code:

double readDouble( void )
{
    double input;

    while (!(cin >> input))
    {
        cout << "Invalid data.\n";
        cin.clear();
        cin.ignore(numeric_limits< double >::max(), '\n');
    }
    return input;
}

I get this warning when compiling on Dev-C++ 4.9.9.2

Code:

68 C:\Projects\CISP400\invdata.cpp [Warning] passing `double' for converting 1 of `std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::ignore(std::streamsize, typename _Traits::int_type) [with _CharT = char, _Traits = std::char_traits<char>]'

Problem is that if I enter a character or any invalid data it goes into the infinite loop that I am trying to avoid. I have the same loop in a function for integers but no problems there.

Look at the defintion of cin.ignore() and the types of its parameters. Then, look at the types you are passing it. In C++, the types of the arguments you send to a function have to match the types of the parameters in the function definition.

Ok, it takes an integer. I tried static_cast 'ing the whole expression to an int but still get infinite loop. Is there any way to do what I'm trying here?

Try:

cin.ignore(numeric_limits<streamsize >::max(), '\n');

Ah, very nice. Much appreciated.