C++ Operator Overload implicit conversion

#include <cstdio>
#include <cstdlib>
#include <iostream>
using namespace std;

class Complex/*  w w w.  j  a  v  a2 s  .  c  o  m*/
{
  public:
    Complex() : dReal(0.0), dImag(0.0)
    { 
        cout << "invoke default constructor" << endl;
    }
    explicit Complex(double _dReal): dReal(_dReal), dImag(0.0){ 
        cout << "invoke real constructor " << dReal <<endl;
    }
    Complex(double _dReal, double _dImag): dReal(_dReal), dImag(_dImag){
        cout << "invoke complex constructor " << dReal << ", " << dImag << endl;
    }

    double dReal;
    double dImag;
};

int main(int argcs, char* pArgs[])
{
    Complex c1, c2(1.0), c3(1.0, 1.0);

    // constructor can be used to convert from one type to another
    c1 = Complex(10.0);

    c1 = (Complex)20.0;
    c1 = static_cast<Complex>(30.0);

    return 0;
}