Passing Arrays To Functions

Programming in Java during CSCE145 and CSCE146 got you used to arrays that “know” their own size. In C++, things work differently.

When passing an array to a function, you don’t get the array’s size “for free.” Instead, you have to provide the array’s size as a separate parameter. This is because C++ doesn’t store the size of the array; it only knows where the array begins.

The following snippet is a prototype of a function that doubles the value of each element in an integer array:

void DoubleValues(int array[], int size);

Here’s the implementation to the previous prototype:

void DoubleValues(int array[], int size) {
  for (int i = 0; i < size; ++i) {
    array[i] *= 2;
  }
}

Finally, this is an example of calling the function and using it on an integer array:

const int kSize = 5;
int array[kSize] = {1, 2, 3, 4, 5};

DoubleValues(array, kSize);

Constant Arrays

Another new concept in C++ is making an array parameter constant. By declaring an array parameter as const, you guarantee that the function won’t alter the original array.

This is particularly helpful for functions like PrintArray or Search,
where the goal is only to read and display the data, not modify it. Using const also communicates the function’s behavior to other developers, making it clear
that the array’s contents remain unchanged after the function call.

First we’ll make a function prototype for a function that prints the values in an integer array:

void PrintArray(const int[], int);

Now we’ll add the implementation:

void PrintArray(const int array[], int size) {
  for (int i = 0; i < size; ++i) {
    cout << array[i] << endl;
  }
}

Finally, lets test the function on an integer array:

const int kSize = 5;
int array[kSize] = {1, 2, 3, 4, 5};

PrintArray(array, kSize);