How to check if the input number integer not float?

Question

I want to check if the input is valid, but when i do run this code I see that it checks only input for charcters. If i input a float number it will take it and going t

Answer 1

You can try to convert the input string to a int using a std::istringstream. If it succeeds then check for eof() (after ignoring blank spaces) to see if the whole input was consumed while converting to int. If the whole input was consumed then it was a valid int.

Something a bit like this:

int input_int()
{
    int i;

   // get the input
    for(std::string line; std::getline(std::cin, line);)
    {
        // try to convert the input to an int
        // if at eof() all of the input was converted - must be an int
        if((std::istringstream(line) >> i >> std::ws).eof())
            break;

        // try again
        std::cout << "Not an integer please try again: " << std::flush;
    }

    return i;
}

int main()
{
    std::cout << "Enter an integer: " << std::flush;

    std::cout << "i: " << input_int() << '\n';
}