clock_member自增自减重载实现

/*代码如下*/

#ifndef CLOCK_H
#define CLOCK_H

class Clock {
    public:
        Clock(int h=0,int m=0, int s=0);
        Clock& operator++();  // 前置++，形如++t
        Clock operator++(int notused);  // 后置++，形如t++
        Clock& operator--();
        Clock operator--(int notused);
        void showTime();
    private:
        int hour,minute, second;
};

#endif

#include "clock.h"
#include <iostream>
#include <cstdlib> 
#include <iomanip>
using namespace std;
        
const int HT = 24;        
        
Clock::Clock(int h,int m, int s):hour(h), minute(m), second(s) {
    
    if(! (hour >= 0 && hour < HT && minute >= 0 && minute < 60 && second >=0 && second < 60 ) ) {
        cout << "时钟值不在合理范围..." << endl;
        exit(0); 
    }
             
}

// ++t 
Clock& Clock::operator++(){
    ++second;
    
    minute += (second / 60);
    second %= 60;
    
    hour += (minute / 60);
    minute %= 60;
    
    hour %= HT;
    
    return *this;
} 

// t++
Clock Clock::operator++(int notused){
    Clock old = *this;
    
    ++(*this);
    
    return old;
}


void Clock::showTime() {
    cout << setw(2) << setfill('0') << hour   <<":" 
         << setw(2) << setfill('0') << minute << ":" 
         << setw(2) << setfill('0') << second << endl;
}

Clock& Clock::operator--() {
    if (second == 0) {
        second = 59;
        if (minute == 0) {
            minute = 59;
            if (hour == 0)
                hour = HT - 1;
        }
    }
    else
        second--;
    return *this;
}
Clock Clock::operator--(int notused) {
    Clock old;
    old = *this;
     --(*this);
     return old;
}

#include "clock.h"
#include <iostream>
using namespace std;

int main() {
    cout << "自减重载:" << endl;
    Clock t1(0,0,0), t2(t1), t3, t4;
    
    t3 = t1--;
    t4 = --t2;
    
    t1.showTime();system("pause");

    t2.showTime();system("pause");

    t3.showTime();system("pause");

    t4.showTime();system("pause");

    cout << "自增重载：" << endl;

    Clock c1(23,59,59), c2(c1), c3, c4;
    
    c3 = c1++;
    c4 = ++c2;
    
    c1.showTime();system("pause");

    c2.showTime();system("pause");

    c3.showTime();system("pause");

    c4.showTime();system("pause");
    
    return 0;
}

/*运行截图*/

临界情况的测试。