14.10. Private functionsΒΆ
In some cases, there are member functions that are used internally by a
class, but that should not be invoked by client programs. For example,
calculatePolar and calculateCartesian are used by the accessor
functions, but there is probably no reason clients should call them
directly (although it would not do any harm). If we wanted to protect
these functions, we could declare them private the same way we do
with instance variables. In that case the complete class definition for
Complex would look like:
class Complex
{
private:
double real, imag;
double mag, theta;
bool cartesian, polar;
void calculateCartesian ();
void calculatePolar ();
public:
Complex () { cartesian = false; polar = false; }
Complex (double r, double i)
{
real = r; imag = i;
cartesian = true; polar = false;
}
void printCartesian ();
void printPolar ();
double getReal ();
double getImag ();
double getMag ();
double getTheta ();
void setCartesian (double r, double i);
void setPolar (double m, double t);
};
The private label at the beginning is not necessary, but it is a
useful reminder.
The active code below updates calculatePolar and calculateCartesian
to be private functions. Notice how we are no longer able to call
calculateCartesian in main. Feel free to modify the code and experiment around!