Arrays as Function Parameters

• When writing a function with an array parameter, we place an empty [] after the parameter name:

  void print(int values[], int size);
  

• We pass the size of the array to the function so the function knows the size of the array
  • There is no size() member function for an array
• When we call the function, we do NOT include the []:

  print(data, size); // function call
  

• Instead, we pass in the name of the array.
  
• Unlike other parameters, you can pass the array into the function and then alter the array inside of the function without needing to return a new array.
  
• For example, what do you think will be the result of running the following program?

#include <iostream>

using namespace std;

void fillArray(int data[], int size) {
    for (int i = 0; i < size; i++) {
       data[i] = i;
    }
} 

        int main() {
            const int SIZE = 5;
            int data[SIZE];
            fillArray(data, SIZE);
            for (int i = 0; i < SIZE; i++) {
                cout << data[i] << endl;
            }
        }

• Note the use of size parameter
• The programmer must keep track of the size when working with arrays
• Note that arrays cannot be function return types
• Returning an array with a return statement is not necessary

Using the const Modifier

• Normally, a function can change the values of array elements
• We can prevent the modification using the const modifier:

  void print(const int values[], int size);
  

• The compiler will issue an error message if you try to change the value of an array element
• If a function with a constant array parameter calls another function using the const array parameter as an argument, the called function must use a const array parameter as well
• Otherwise, the compiler will issue an error
• The following program shows arrays used with functions

Activity 20.3: Exploring Arrays (10 pts)

• In this exercise we explore declaring, allocating and assigning values to arrays containing lists of data.
• Create a source code file called myarrays.cpp:
• Add the following function to the code:

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

• Compile your code to make sure it has correct syntax.

  If you have problems, ask a classmate or the instructor for help as needed.

• Declare and initialize an array for a list of 10 integer scores after the current arrays using the following code:

  const int NUM_SCORES = 10;
  int scores[NUM_SCORES] = {90, 91, 92, 93, 94, 95, 96, 97, 98, 99};
  

• After declaring and initializing the array, call the print() function using the code:

  cout << "Integer scores:\n";
  print(scores, NUM_SCORES);

• Compile and run the program to make sure you made the changes correctly. When you run the program, the output should look like:

  Integer scores:
  90 91 92 93 94 95 96 97 98 99
  

• Declare and initialize an array of double values holding the the temperature values 25.7, 30.3, and 40.9
  
• Write another print() function with two parameters: one for the array of double values and one for the size of the array.
• Note that you may also name this function print. The compiler will know they are different functions as their parameters are different.
• This is called function overloading (two functions with the same name, but different parameters in the same program)
  
• After declaring and initializing the array, call the print() function.
• Compile and run the program to make sure you made the changes correctly. When you run the program, the output should look like:

  Integer scores:
  90 91 92 93 94 95 96 97 98 99
  Double temperatures:
  25.7 30.3 40.9
  

• Declare and allocate an array of char values and assign it the vowels a, e, i, o and u.

  After declaring and initializing the array, write another print function to display it. Again, this method should be named print(). Then, call this method in main.
  

  Compile and run the program to make sure you made the changes correctly. When you run the program, the output should look like this:

  Integer exam scores:
  90 91 92 93 94 95 96 97 98 99
  Double temperatures:
  25.7 30.3 40.9
  Char vowels:
  a e i o u 
  

• Finally write a function called addExtraCredit with the following signature:

void addExtraCredit(int scores[], int size){

    //fill in method body here

}

• This method should add 5 points of extra credit to each value in the scores array.
  
• Hint: Add 5 to each array element using a for loop to iterate through all values in the scores array.
  
• Write the function and then call it on the scores array like so:

addExtraCredit(scores, NUM_SCORES);

• Now print out the scores array by calling the print function to verify that the extra credit got added correctly.
• Your output should now look like the following:

Integer exam scores:
90 91 92 93 94 95 96 97 98 99
Double temperatures
25.7 30.3 40.9
Char vowels:
a e i o u
Exams scores with extra credit
95 96 97 98 99 100 101 102 103 104

• Submit your program to Canvas when you are finished.