The first public function we encounter is a so-called
constructor, which tells how we declare a variable of type Complex
and how this variable is initialized. We have chose three possibilities in the example above:
A declaration like Complex c; calls the member function Complex() which can have the following implementation
Complex:: Complex () { re = im = 0.0; }
meaning that it sets the real and imaginary parts to zero. Note the way a member function is defined. The constructor is the first function that is called when an object is instantiated.