重载++后缀运算符

问题描述

#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;
	}

	Time& operator++()
	{
		++minutes;
		if (minutes>=60)
		{
			++hours;
			minutes = minutes - 60;
		}
		return *this;
	}

	Time& Time::operator++(int){

		Time temp(hours, minutes);
		minutes++;
		if (minutes >= 60)
		{
			hours++;
			minutes = minutes - 60;
		}
		return *this;
	}

};

int main() {
	Time T1(11, 59), T2(10, 40);

	T2 = ++(++T1); //
	T1.displayTime();        // display 12,01 ok
	T2.displayTime();        // display 12,01 ok

	T2 = (T1++)++;
	T1.displayTime();        // display 12,03 οκ
	T2.displayTime();        // display 12,03 why?? i think it must be 12,01

	return 0;
}

我的尝试：



问题出在对象T2

What I have tried:

The problem is at the object T2

推荐答案

T2 = ++(++T1);

1.你在括号中增加T1

2.你增加大括号外的T1

3.你将 T1值分配给T2



提示：使用调试器步骤进入此代码行的三个函数调用。

1. you increment the T1 in the braces
2. you increment the T1 outside the braces
3. you assign the T1 values to T2

tip: use a debugger to step into the three function calls of this code line.

Time operator++(int)
{
    Time temp(hours, minutes);
    minutes++;
    if (minutes >= 60)
    {
        hours++;
        minutes = minutes - 60;
    }
    // Return unchanged object here!
    return temp;
}

另请参阅 []。

使用后缀实现中的前缀增量：

See also Increment and Decrement Operator Overloading (C++)[^].
That uses the prefix increment within the postfix implementation:

Time operator++(int)
{
    Time temp = *this;
    *++this;
    return temp;
}

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