C++ 增量++和减-重载

• 

  增量++和减-重载

  增量（++）和减量（-）运算符是C++中可用的两个重要的一元运算符。下面的示例说明如何为前缀以及后缀用法重载增量（++）运算符。同样，您可以重载运算符（-）。

  
  #include <iostream> 
  
  using namespace std;
   
  class Time {
     private:
        int hours;             // 0 to 23
        int minutes;           // 0 to 59
        
     public:
        // required constructors
        Time() {
           hours = 0;
           minutes = 0;
        }
        Time(int h, int m) {
           hours = h;
           minutes = m;
        }
        
        // method to display time
        void displayTime() {
           cout << "H: " << hours << " M:" << minutes << endl;
        }
        
        // overloaded prefix ++ operator
        Time operator++ () {
           ++minutes;          // increment this object
           if(minutes >= 60) {
              ++hours;
              minutes -= 60;
           }
           return Time(hours, minutes);
        }
        
        // overloaded postfix ++ operator
        Time operator++( int ) {
        
           // save the orignal value
           Time T(hours, minutes);
           
           // increment this object
           ++minutes;                    
           
           if(minutes >= 60) {
              ++hours;
              minutes -= 60;
           }
           
           // return old original value
           return T; 
        }
  };
  
  int main() {
     Time T1(11, 59), T2(10,40);
   
     ++T1;                    // increment T1
     T1.displayTime();        // display T1
     ++T1;                    // increment T1 again
     T1.displayTime();        // display T1
   
     T2++;                    // increment T2
     T2.displayTime();        // display T2
     T2++;                    // increment T2 again
     T2.displayTime();        // display T2
     return 0;
  }
  

  尝试一下

  编译并执行上述代码后，将产生以下结果-

  
  H: 12 M:0
  H: 12 M:1
  H: 10 M:41
  H: 10 M:42