//cons.cpp  -- @CopyLeft by tsaiwn@csie.nctu.edu.tw
//demo Inheritance and constructor usage, as well as friend function
#include <iostream>
using namespace std;
class gg{ public:
   gg( ) { cout << " ggg\n"; }
   ~gg( ) { cout << " gg dying; "; }
   gg(int) { cout << "g38"<<endl; }
   gg(double){ cout << "g49"<<endl; }
}; // gg
struct yy:public gg{
   yy( ) { cout << " YYY"<<endl; }  
   yy(int x):gg(x) { ddd=x; cout << "Y38\n"; } //super(x) in Java
   yy(double x){ cout << "Y4.9\n"; www=x;}  // 注意等同 super( )
   friend ostream& operator<<(ostream&, const yy&);
   friend class zz;   // 該 class zz 內所有 function 都是 friend
   // friend is the ONLY one who can touch your private
   ~yy( ) { cout << " yy "<<ddd<<" dying\n"; }
 protected: int ddd;  double www;    // can be used in derived class
}; // yy
class zz { public:
   zz( ){cout<< "zz\n";}  ~zz( ){cout<<"zz "<<getd( )<<" dying\n"; }
   zz(int x):c(x) { cout << "Z58"<<endl; }
   zz(double x) { cout << "ZDouble"<<endl; }  // 沒指定 super
   int getd( ) const { return c.ddd; }
   double getw( ) const { return c.www; }
   friend ostream& operator<<(ostream&, const zz&);
 private: yy c;  // my private data
}; // zz
gg g;  
yy y;  yy y22(58); yy y99(49.35);
int main( ) {
   cout << "Welcom to C++ Disney Land..." << endl;
   zz a;  zz bzz(88);  zz ddzz(38.49);
   //cout << "g=" << g << endl;   // required operator<<
   cout << "y=" << y << endl;
   cout << "y22=" << y22 << endl;
   cout << "y99=" << y99 << endl;
   cout << "bzz=" << bzz << endl;
}
ostream& operator<<(ostream& river, const yy& x){
   river << x.ddd << ", " << x.www;
   return river;
}// operator<<
ostream& operator<<(ostream& river, const zz& x){
   river << x.getd( ) << ", " << x.getw( ); return river;
}// operator<<
/*********************
F:\COURSE\STL>g++ cons.cpp

F:\COURSE\STL>a
 ggg
 ggg            <====== 這和以下 YYY 是 yy y; 引起的
 YYY
g38            <====== 這和以下 Y38 是 yy y22(58); 引起的
Y38
 ggg            <====== 這和以下 Y4.9 是 yy y99(49.35); 引起的
Y4.9
Welcom to C++ Disney Land...
 ggg      <====== 這和以下 YYY 和 zz 共三列是 zz a; 引起的
 YYY
zz
g38      <====== 這和以下 Y38 和 Z58 共三列是  zz bzz(88); 引起的
Y38
Z58
 ggg  <===== 這和以下 YYY 和ZDouble共三列是 zz ddzz(38.49); 引起的
 YYY
ZDouble
y=0, 0
y22=58, 0
y99=0, 49.35
bzz=88, 6.55442e+268
zz 2009056206 dying
 yy 2009056206 dying
 gg dying; zz 88 dying
 yy 88 dying
 gg dying; zz 2009118740 dying
 yy 2009118740 dying
 gg dying;  yy 0 dying
 gg dying;  yy 58 dying
 gg dying;  yy 0 dying
 gg dying;  gg dying;
****************************/