Question

Give an example where an argument should be passed by reference.

Short answer

Answer: Passing arguments by reference in the given example allows the function to directly modify the original variable values, thus swapping their values successfully. This saves memory and processing time as it doesn't create a copy of the variables.

Step-by-step solution

Example: Swapping Two Values

Let's consider a simple function that swaps the values of two integer variables. In this case, we should pass the arguments by reference so that the original values of the variables are modified. Here's a step-by-step solution: 1. Define a function `swap` with two integer parameters, passed by reference. 2. Within the `swap` function, use a temporary variable to store the value of the first parameter. 3. Assign the value of the second parameter to the first parameter. 4. Assign the value of the temporary variable (originally the value of the first parameter) to the second parameter. 5. The values of the original variables are now swapped. Here's the code for this example: ```cpp #include void swap(int &a, int &b) { int temp = a; a = b; b = temp; } int main() { int x = 5; int y = 10; std::cout << "Before swapping: x = " << x << ", y = " << y << std::endl; swap(x, y); std::cout << "After swapping: x = " << x << ", y = " << y << std::endl; return 0; } ``` In this example, the `swap` function accepts two integer arguments by reference, allowing it to directly modify their values. The variables `x` and `y` are swapped within the `swap` function, and since they are passed by reference, the change is also reflected in the `main` function.