構造函數重載(Overloading constructors)

 std;

 Rectangle {
     width, height;
  :
    Rectangle ();
    Rectangle ();
     area () { (width*height);}
};

Rectangle::Rectangle () {
  width = 5;
  height = 5;
}

Rectangle::Rectangle (int a,  b) {
  width = a;
  height = b;
}

 main () {
  Rectangle rect (3,4);
  Rectangle rectb;
  cout << "rect area: " << rect.area() << endl;
  cout << "rectb area: " << rectb.area() << endl;
   0;
}

(default constructor)。默認構造函數是的，它之所以特殊，是因為

，如果寫上，則不能調用 默認構造函數：