hour14_3.cpp

《24学时精通c++》的随书源码的下半部分。欢迎下载学习。

 // Listing 14.5
 //Overload operator plus (+)
 #include <iostream>
 
 class Counter
 {
 public:
     Counter();
     Counter(int initialValue);
     ~Counter(){}
     int GetItsVal()const { return itsVal; }
     void SetItsVal(int x) {itsVal = x; }
     Counter operator+ (const Counter &);
     Counter operator- (const Counter &);   // very important!
 private:
     int itsVal;
 };
 
 Counter::Counter(int initialValue):
 itsVal(initialValue)
 {}
 
 Counter::Counter():
 itsVal(0)
 {}
 
 Counter Counter::operator+ (const Counter & rhs)
 {
     return Counter(itsVal + rhs.GetItsVal());
 }

 Counter Counter::operator- (const Counter & rhs)    // overloaded subtraction operator
 {
     return Counter(itsVal - rhs.GetItsVal());
 }
 
 int main()
 {
     Counter varOne(2), varTwo(4), varThree;
     varThree = varOne - varTwo;
     std::cout << "varOne: " << varOne.GetItsVal()<< std::endl;
     std::cout << "varTwo: " << varTwo.GetItsVal() << std::endl;
     std::cout << "varThree: " << varThree.GetItsVal() 
         << std::endl;

     varThree = varTwo - varOne;
     std::cout << "varOne: " << varOne.GetItsVal()<< std::endl;
     std::cout << "varTwo: " << varTwo.GetItsVal() << std::endl;
     std::cout << "varThree: " << varThree.GetItsVal() 
         << std::endl;

     return 0;
 }