Check if input is integer

Question

In order to learn C++, I\'m translating a program I wrote in Python.

I wrote this

n = 0
while n < 2:
    try:
        n = int(raw_input(\'Please inser         


        

Answer 1

Your Python can code be translated more directly if you use C++11's std::stoi combined with std::getline to read a whole line of input. This is much easier than struggling with standard I/O error handling, which arguably does not have a very user-friendly interface.

std::stoi throws std::invalid_argument if the input could not be correctly parsed as an integer number, and std::out_of_range if the number is too small or too big to fit in an int.

#include 
#include 

int main() {
    int n = 0;
    while (n < 2) {
        std::cout << "Please insert an integer bigger than 1: ";
        std::string input;
        std::getline(std::cin, input);
        try {
            n = std::stoi(input);
        } catch (std::exception const&) {
            std::cerr << "ERROR!\n";
        }
    }
}

If you want to make the code even more similar to its Python equivalent, then you can encapsulate the input in a function:

#include 
#include 

int raw_input(std::string const& message)
{
    std::cout << message;
    std::string input;
    std::getline(std::cin, input);
    return std::stoi(input);
}

int main() {
    int n = 0;
    while (n < 2) {
        try {
            n = raw_input("Please insert an integer bigger than 1: ");
        } catch (std::exception const&) {
            std::cout << "ERROR!\n";
        }
    }
}