Functions asking for user input, with default prompts

Question

I succeeded in the first part of the exercise, this attempt is the second part. I am not sure I have accomplished the goal, and would appreciate the input of more knowledgeable minds. As always, critiques of my techniques welcome.

This is an exercise from the book titled 'Beginning C++ through Game Programming' by Michael Dawson.

Challenge me, despite my novice level of understanding.

The exercise:

Using default arguments, write a function that asks the user for a number and returns that number. The function should accept a string prompt from the calling code. If the caller doesn't supply a string for the prompt, the function should use a generic prompt.

Next, using function overloading, write a function that achieves the same results.

My code:

// Chapter 05, Exercise 03: Beginning C++ through Game Programming

/*  Using default arguments, write a function that asks the user for a 
    number and returns that number. The function should accept a string
    prompt from the calling code. If the caller doesn't supply a string
    for the prompt, the function should use a generic prompt. 

    Next, using function overloading, write a function that achieves 
    the same results.
*/

#include <iostream>
#include <string>

int askNumberFn(int number, std::string prompt = "Please enter a number, now: "); // default arguments must come last, in order of excecution
std::string askNumberFn(std::string prompt = "Please type a number, now: "); // default parameters must be different in order to overload Fn

char exitTimeFn();

int main()
{
    askNumberFn("Please type a number: "); // We require the calling code to return a prompt
    askNumberFn(); // We also require the Fn to return a default prompt

    int number = 0;
    number = askNumberFn(number, "Please enter a number: "); // To prove we have overloaded the FN, we require the Fn to also return an int

    number = 0; // We return the value of number to zero, in order to remove any doubt, if we input the same number again
    number = askNumberFn(number); // Lastly, we have to prove our overloaded Fn displays a default prompt 

    exitTimeFn();
    return 0;
}

int askNumberFn(int number, std::string prompt)
{
    std::cout << prompt;
    std::cin >> number;
    std::cout << "You entered the number: " << number << std::endl;
    return number;
}

std::string askNumberFn(std::string prompt)
{
    std::string word;
    std::cout << prompt;
    std::cin >> word;
    std::cout << "You typed the number: " << word << std::endl;
    return word;
}

char exitTimeFn()
{
    char exitNow;
    std::cout << "Press 'x' to exit: ";
    std::cin >> exitNow;
    return exitNow;
}

Answer 1

Correctness: There are some cases that aren't handled. What happens if the user enters a word instead of a number? What if the user enters 2.1? The program will exit regardless of what character the user enters when exitTimeFn() is called.

I think your overload was a clever solution to a vague instruction. To make it clear that the extra parameter is irrelevant, you could comment out the name. For example:

int askNumberFn(int /*number*/, std::string prompt)
{
    int number;
    std::cout << prompt;

Because parameters are used to supply data to functions, it doesn't make sense to pass in a value, then immediately re-assign it before use.

Parameters: I would pass the strings by const reference instead of by value.

Naming: No need for Fn at the end of every function. It's obvious that it's a function from how it's used. The names could also be slightly more descriptive: getNumberFromUser, showExitDialogue, for example.

Commenting: Generally, I'd discourage line-by-line comments explaining what each line of code is doing. It's usually a sign you need to write clearer code. The way you use it in your main function to document your testing has some merit, I think. Look into unit testing for a more scalable/professional way of doing the same thing.

If accidentally using the same input for testing is a concern, I'd just use a different variable completely. A unit testing library would provide better tools to handle this.

While I believe this fulfils the question literally, there is an implied task of reacting reasonably to invalid input. I would test more thoroughly and make sure the edges don't do anything surprising.