Returning multiple values using pointers in a function

Question

Can anyone help me to understand how to return multiple values using pointers in a function? I am confused with the following example.

Can we assign other values to int value besides 0 or 1, while the program can still run normally?
What does defining the value of 0 and 1 in the if statement and else statement do for us in the int factor function?
What does if(!error) statement do in the main ()?

#include <iostream>
using namespace std;

int factor(int n, int *p_addition, int *p_subtraction, int *p_squared, int *p_cubed)
{
    int value = 0;
    if (n >= 0 && n <= 100)
    {
        *p_addition = n + n;
        *p_subtraction = n - n;
        *p_squared = n*n;
        *p_cubed = n*n*n;
        value = 0;
    }
    else
    {
        value = 1;
    }
    // This function will return a value of 0 or 1
    return value;
}

int main()
{
    int number, num_add, num_sub, squared, cubed;
    int error;

    cout << "Enter a number between 0 and 100: ";
    cin >> number;

    error = factor(number, &num_add, &num_sub, &squared, &cubed);

    if (!error)
    {   
        cout << "number: " << number << endl;
        cout << "num_add: " << num_add << endl;
        cout << "num_sub: " << num_sub << endl;     
        cout << "squared: " << squared << endl;
        cout << "cubed: " << cubed << endl;
    }
    else
    {
        cout << "Error encountered!!" << endl;
    }
    return 0;
}

https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list I think that your questions are better addressed by a tutorial. SO doesn't aim at teaching a language from scratch. Also, perhaps take the [tour] and read [ask]. — Ulrich Eckhardt, Feb 19 '22 at 08:07
@TedKleinBergman All questions seem to be more or less related to int->bool implicit conversion, so I think it to be ok to keep it together — Sebastian, Feb 19 '22 at 08:37

Sebastian · Answer 1 · 2022-02-19T08:44:30.903

int is at least 16 bits (depending on the system - hardware, operating system, 32-bit computing / vs. 64-bit computing), for numeric range, cf: https://en.cppreference.com/w/cpp/language/types (at least -32768 to 32767 for 16 bit integers).
factor contains return value, which (here) signifies to the caller, whether an error occurred. It has no other effect within factor.
The ! negates the boolean value, so that the test is for false. if with an int implicitly converts to bool and tests for error being 0: https://en.cppreference.com/w/cpp/language/implicit_conversion#Boolean_conversions The value zero (for integral [...]) [...] become[s] false. All other values become true.

So any value beside 0 would have the same effect instead as 1.

It would have been better to name value something like wrong_input_range.

It would have been better to make value a bool type instead of int and make the return type of factor bool, too.

Whether your main returns a value beside 0 in case of the error, you can decide by yourself. Within a script, the returned value of called programs often is tested to know, whether the script can continue.

Returning multiple values using pointers in a function

1 Answers1