Swap By Reference

Functions can take references when they need to update caller-owned values directly.

swap_by_reference.cpp

#include <iostream>

void swap_values(int& left, int& right) {
    int saved = left;
    left = right;
    right = saved;
}

int main() {
    int first = ;
    int second = 9;

    swap_values(first, second);

    std::cout << "first=" << first << std::endl;
    std::cout << "second=" << second << std::endl;
    return 0;
}

#include <iostream>

void swap_values(int& left, int& right) {
    int saved = left;
    left = right;
    right = saved;
}

int main() {
    int first = ;
    int second = 9;

    swap_values(first, second);

    std::cout << "first=" << first << std::endl;
    std::cout << "second=" << second << std::endl;
    return 0;
}

#include <iostream>

void swap_values(int& left, int& right) {
    int saved = left;
    left = right;
    right = saved;
}

int main() {
    int first = ;
    int second = 9;

    swap_values(first, second);

    std::cout << "first=" << first << std::endl;
    std::cout << "second=" << second << std::endl;
    return 0;
}

reference parameter A non-const reference parameter allows a function to update the caller's variable.

swap Swapping through reference parameters changes both variables outside the function.