C++ calculator

Question

I'm tryin to make a cpp calculator but idk how do I make the user to input a int instead of str.
basiclly when someone inputs a string I want it to print ,,That isn't a number"
How do I do that?

Answer 1

int input;
if (!(std::cin >> input))
std::cerr << "Your input could not be validated, did you provide something else than a number?\n";

Answer 2

It's if you don't want to use the std namespace: https://youtu.be/4NYC-VU-svE

Answer 3

Yes, it groups classes, functions and globals, mainly to avoid name conflicts between libraries.

Answer 4

namespace example
{
class Something {…};
void foo(){…};
}

int main()
{
example::foo();
}

//or
using namespace example;
int main()
{
foo();
}

Answer 5

Oh but what does ,,std" and ,,::" do?
Also why is there ,,!" in the parenthases?

Answer 6

I'm new so I don't really understand what std and namespace is. Is namespace like a library similar like you ,,import (Library name)" in Python 3?

Answer 7

oh god I still don't get it lol

Answer 8

https://code.sololearn.com/css6v6sL3vIv/?ref=app