C++前置和后置运算符的区别

如果后面的括号里带有形参则为后置单目运算符重载，无形参则为前置单目运算符重载。

#include <iostream>
using namespace std;
//创建时钟类
class Clock
{
public:
 Clock(int NewH=0,int NewM=0,int NewS=0);//构造函数
 void ShowTime();//显示时间函数声明
 Clock& operator ++();//前置运算符重载
 Clock operator ++(int);//后置运算符重载
 //关于前置运算符的后置运算符的重载说明：如果后面的括号里带有形参则为后置单目运算符重载，或无形参则为前置单目运算符重载
private:
 int Hour,Minute,Second;
};
//构造函数实现
Clock::Clock(int NewH,int NewM,int NewS)
{
 if(0<=NewH && NewH<24 && 0<=NewM&&NewM<60&&0<=NewS && NewS<60)
 {
  Hour = NewH;
  Minute=NewM;
  Second=NewS;
 }
 else
  cout<<"Time error!"<<endl;
}
//显示时间函数实现
void Clock::ShowTime()
{
 cout<<Hour<<":"<<Minute<<":"<<Second<<endl;
}
//前置单目运算符重载实现
Clock& Clock::operator ++()//前置单目运算符重载函数
{
 Second++;
 if(Second>=60)
 {
  Second = Second-60;
  Minute++;
  if(Minute>=60)
  {
   Minute = Minute - 60;
   Hour++;
   Hour=Hour%24;
  }
 }
 return *this;
}
//后置单目运算符重载实现
Clock Clock::operator ++(int)//后置单目运算符重载
{
 Clock old = *this;
 ++(*this);
 return old;
}
void main()
{
 Clock myClock(23,59,59);
 cout<<"First time output:";
 myClock.ShowTime();
 cout<<"Show myClock++:";
 (myClock++).ShowTime();
 cout<<"Show ++myClock:";
 (++myClock).ShowTime();
}