Computer Science - Object Oriented Programming Using C++ - Discussion

Ex.
int add(int a, int b, int c= 50).
Default argument are declared from righ- hand side.

Call add(10,20)
a=10, b=20 and c=50 is default value.

void printValues(int x, int y=10) // 10 is the default argument, y is now an optional parameter
{
std::cout << "x: " << x << '\n';
std::cout << "y: " << y << '\n';
}

int main()
{
printValues(1); // y will use default argument 10
printValues(3, 4); // y will use user-supplied argument 4
}

This program produces the following output:
x: 1
y: 10
x: 3
y: 4

@All.

If you want to override constructor default values for an object you are instantiating, you must also override.

B. all parameters to the left of that value.

Things to Remember:-

Once we provide a default value for a parameter, all subsequent parameters must also have default values.

For example:

// Invalid
void add(int a, int b = 3, int c, int d);

// Invalid
void add(int a, int b = 3, int c, int d = 4);

// Valid
void add(int a, int c, int b = 3, int d = 4);