list1012.cpp

teach yourself C++ in 21 days 第五版

// Listing 10.12 - Prefix and Postfix operator overloading

#include <iostream>

using namespace std;

class Counter
{
  public:
    Counter();
    ~Counter(){}
    int GetItsVal()const { return itsVal; }
    void SetItsVal(int x) {itsVal = x; }
    const Counter& operator++ ();      // prefix
    const Counter operator++ (int); // postfix

  private:
    int itsVal;
};

Counter::Counter():
itsVal(0)
{}

const Counter& Counter::operator++()
{
   ++itsVal;
   return *this;
}

const Counter Counter::operator++(int theFlag)
{
   Counter temp(*this);
   ++itsVal;
   return temp;
}

int main()
{
   Counter i;
   cout << "The value of i is " << i.GetItsVal() << endl;
   i++;
   cout << "The value of i is " << i.GetItsVal() << endl;
   ++i;
   cout << "The value of i is " << i.GetItsVal() << endl;
   Counter a = ++i;
   cout << "The value of a: " << a.GetItsVal();
   cout << " and i: " << i.GetItsVal() << endl;
   a = i++;
   cout << "The value of a: " << a.GetItsVal();
   cout << " and i: " << i.GetItsVal() << endl;
   return 0;
}