//cat.cpp -- by tsaiwn
// test default constructor, copy constructor, assignment operator, 
// and operator overloading: operator<<, operator+, ...
#include <iostream>
using namespace std;
class Cat {
     int wet;
  public:
   Cat( ) { wet=0; cout << "( " << wet<< " born. ";}
   Cat(int x){wet=x; cout << "( " << wet<< " appears. ";}
   Cat(const Cat& x){wet=x.wet; cout << "( " << wet<< " Copy. ";}
   Cat& operator=(const Cat&x) {wet=x.wet; cout << " [op] "; return *this;}
   Cat& operator+(const Cat&x) {wet += x.wet; cout << "=add= "; return *this;}
   friend ostream& operator<<(ostream&river, const Cat&);
   ~Cat( ) { cout << "[" << wet << "dying. "; }
};
int main( ) {
    Cat x;
    Cat y(x);  // copy constructor
    Cat m(38); // Cat(int)
    cout << "x=" << x << endl;
    cout << "y=" << y << ",  m=" << m << endl;
    cout << "\n--------\n";
    m = x+y;
    cout << "m=" << m << endl;
    cout << "\n-------- --------\n";
    m = x+ 38;
    cout << "m=" << m << endl;
}
ostream& operator<<(ostream&river, const Cat&x) {
   river << x.wet;
   return river;
}
/******
C:\cpp>g++ cat.cpp

C:\cpp>a
( 0 born. ( 0 Copy. ( 38 appears. x=0
y=0,  m=38

--------
=add=  [op] m=0

-------- --------
( 38 appears. =add=  [op] [38dying. m=38
[38dying. [0dying. [38dying.

C:\cpp>

******/