Why isn't a function parameter used here?

Question

I'm going through this tutorial: https://www.learncpp.com/cpp-tutorial/how-to-design-your-first-programs/ I noticed the author didn't use a parameter in this function:

int getUserInput()
{
    std::cout << "Enter an integer ";
    int input{};
    std::cin >> input;

    return input;
}

Would it be okay to do something like this?

int getUserInput(int input)
{
    std::cout << "Enter an integer ";
    std::cin >> input;

    return input;
}

Answer 1

It would work, but it wouldn't make much sense.

The first version of your function is used something like this:

int some_number = getUserInput();

That makes sense; the caller isn't providing any input to the function, so it takes no parameters.

---

The second version takes a parameter though, so the caller has to provide it. The function doesn't actually do anything with that value though. All of the following behave exactly the same:

int some_number1 = getUserInput(0);
int some_number2 = getUserInput(123456);
int some_number3 = getUserInput(some_number2);

It makes no sense for the caller to provide a parameter to the function since the function doesn't use it at all.