C++ Reference Parameters

C++ supports 3 basic types of parameter passing:
1. pass-by-value
2. pass-by-address
3. pass-by-reference
Pass-by-reference is what Java does - everything is a reference.
The difference is that with reference parameters, you do not explicitly de-reference the variable; it is done automatically for you.

Here are 3 code snippets; create a C++ program called testParams that uses them:

Pass-by-value

double  average2NumsV(double num1, double num2)
{
    double sum;
    double average;

    cout << "V1. num1 is: " << num1 << endl;
    sum = num1 + num2;
    average = sum / 2.0;
    
    num1 = 0;

    cout << "V2. num1 is: " << num1 << endl;
    return(average);
}

Pass-by-address

double  average2NumsA(double *num1, double *num2)
{
    double sum;
    double average;

    cout << "A1. num1 is: " << *num1 << endl;
    sum = *num1 + *num2;
    average = sum / 2.0;
    
    *num1 = 0;
    cout << "A2. num1 is: " << *num1 << endl;
    return(average);
}

Pass-by-reference

double  average2NumsR(double &num1, double &num2)
{
    double sum;
    double average;

    cout << "R1. num1 is: " << num1 << endl;
    sum = num1 + num2;
    average = sum / 2.0;
    
    num1 = 0;
    cout << "R2. num1 is: " << num1 << endl;
    return(average);
}

What happens with each of the calls below? Code 1-3 in your main() first.

double x; double y;

Before each call, set x and y:

x = 80.5; y = 90.5;


cout << average2NumsV(x, y);
cout << average2NumsA(x, y);
cout << average2NumsR(x, y);

cout << average2NumsV(10.0, 8.0);
cout << average2NumsA(10.0, 8.0);
cout << average2NumsR(10.0, 8.0);