详解C++编程中一元运算符的重载

// increment_and_decrement1.cpp
class Point
{
public:
  // Declare prefix and postfix increment operators.
  Point& operator++();    // Prefix increment operator.
  Point operator++(int);   // Postfix increment operator.

  // Declare prefix and postfix decrement operators.
  Point& operator--();    // Prefix decrement operator.
  Point operator--(int);   // Postfix decrement operator.

  // Define default constructor.
  Point() { _x = _y = 0; }

  // Define accessor functions.
  int x() { return _x; }
  int y() { return _y; }
private:
  int _x, _y;
};

// Define prefix increment operator.
Point& Point::operator++()
{
  _x++;
  _y++;
  return *this;
}

// Define postfix increment operator.
Point Point::operator++(int)
{
  Point temp = *this;
  ++*this;
  return temp;
}

// Define prefix decrement operator.
Point& Point::operator--()
{
  _x--;
  _y--;
  return *this;
}

// Define postfix decrement operator.
Point Point::operator--(int)
{
  Point temp = *this;
  --*this;
  return temp;
}
int main()
{
}

friend Point& operator++( Point& )   // Prefix increment
friend Point& operator++( Point&, int ) // Postfix increment
friend Point& operator--( Point& )   // Prefix decrement
friend Point& operator--( Point&, int ) // Postfix decrement

// increment_and_decrement2.cpp
class Int
{
public:
  Int &operator++( int n );
private:
  int _i;
};

Int& Int::operator++( int n )
{
  if( n != 0 )  // Handle case where an argument is passed.
    _i += n;
  else
    _i++;    // Handle case where no argument is passed.
  return *this;
}
int main()
{
  Int i;
  i.operator++( 25 ); // Increment by 25.
}