Question

我正在尝试让重载的postfix运算符make day = 1每当第365天第一次剪切是我创建原型时，第二个片段是实际的代码定义，我似乎无法解决这个问题。任何帮助，将不胜感激。基本上该程序会询问用户一年中哪一天他们想要日期。

所以这一天可能是364，即12月30日。

我希望++运算符在每天使用它来增加当天为365的对象时将这一天带回第1天。如果对象不是365，我只希望它增加1天

每当我将其更改为if（day == 365）它做同样的事情，它仍然增加1，但我最终得到366，而不是1。

我很感激帮助。这是一个家庭作业，但它让我st脚。编辑：发布更多代码。再次感谢帮助人员

#include<iostream>
#include<string>

using namespace std;

class DayOfYear {            
    public:
        DayOfYear(int d);
        void print();
        static string month;
        DayOfYear();
        DayOfYear(string m, int d);
        DayOfYear operator++(int);
        int day;    
};

string DayOfYear::month;

DayOfYear DayOfYear::operator++(int) {
    DayOfYear temp = *this;    

    if (day == 365) {
        day = 1;
    } else {
        day++;
    }

    return temp;
}

DayOfYear::DayOfYear(string m, int d) {
    month = m;
    day = d;

    if (m == "January" && d > 31) {
        cout << "ERROR: PROGRAM TERMINATING!" << endl;
        system("pause");
        exit(0);
    } else if (m == "February" && d > 28) {
        cout << "ERROR INVALID DATE: PROGRAM TERMINATING!" << endl;
        system("pause");
        exit(0);
    } else if (m == "March" && d > 31) {
        cout << "ERROR INVALID DATE: PROGRAM TERMINATING!" << endl;
        system("pause");
        exit(0);
    } else if (m == "April" && d > 30) {
        cout << "ERROR INVALID DATE: PROGRAM TERMINATING!" << endl;
        system("pause");
        exit(0);
    } else if (m == "May" && d > 31) {
        cout << "ERROR INVALID DATE: PROGRAM TERMINATING!" << endl;
        system("pause");
        exit(0);
    } else if (m == "June" && d > 30) {
        cout << "ERROR INVALID DATE: PROGRAM TERMINATING!" << endl;
        system("pause");
        exit(0);
    } else if (m == "July" && d > 31) {
        cout << "ERROR INVALID DATE: PROGRAM TERMINATING!" << endl;
        system("pause");
        exit(0);
    } else if (m == "August" && d > 31) {
        cout << "ERROR INVALID DATE: PROGRAM TERMINATING!" << endl;
        system("pause");
        exit(0);
    } else if (m == "September" && d > 30) {
        cout << "ERROR INVALID DATE: PROGRAM TERMINATING!" << endl;
        system("pause");
        exit(0);
    } else if (m == "October" && d > 31) {
        cout << "ERROR INVALID DATE: PROGRAM TERMINATING!" << endl;
        system("pause");
        exit(0);
    } else if (m == "November" && d > 30) {
        cout << "ERROR INVALID DATE: PROGRAM TERMINATING!" << endl;
        system("pause");
        exit(0);
    } else if (m == "December" && d > 31) {
        cout << "ERROR INVALID DATE: PROGRAM TERMINATING!" << endl;
        system("pause");
        exit(0);
    }

    cout << month << " " << day << endl; 
}

DayOfYear::DayOfYear() {
    cout << "Enter a day number." << endl;
    cin >> day;
    print();
}

DayOfYear::DayOfYear(int d) {
    day = d;

    while (d > 365 || d < 1) {
        cout << "Day can't be higher than 365 and must be at least one. " << endl;
        cin >> d; 
        day = d; 
    }

    print();
}

void DayOfYear::print() {
    if (day > 0 && day < 32) //jan 31 
    {
        month = "January";
        cout << month << " " << 31 + day - 31 << endl;
    }
    else if (day > 31 && day < 60) // feb 28
    {
        month = "February";
        cout << month << " " << day - 31  << endl;
    }
    else if (day > 59 && day < 91) // march 31
    {
        month = "March";
        cout << month << " " << day - 59 << endl;
    }
    else if (day > 90 && day < 121) // april 30 
    {
        month = "April";
        cout << month << " " << day - 90 << endl;
    }
    else if (day > 120 && day < 152) //may 31
    {
        month = "May";
        cout << month << " " << day - 120 << endl;
    }
    else if (day > 151 && day < 182) //june 30
    {
        month = "June";
        cout << month << " " << day - 151 << endl;
    }
    else if (day > 181 && day < 213) //july 31
    {
        month = "July";
        cout << month << " " << day - 181 << endl;
    }
    else if (day > 212 && day < 244) // august 31
    {
        month = "August";
        cout << month << " " << day - 212 << endl;
    }
    else if (day > 243 && day < 274) // sept 30
    {
        month = "September";
        cout << month << " " << day - 243 << endl;
    }
    else if (day > 273 && day < 305) // oct 31
    {
        month = "October";
        cout << month << " " << day - 273 << endl;
    }
    else if (day > 304 && day < 335) // nov 30
    {
        month = "November";
        cout << month << " " << day - 304  << endl;
    }
    else if (day > 334 && day < 366) //dec 31
    {
        month = "December";
        cout << month << " " << day - 334 << endl;
    }
}


int main() {
    DayOfYear day;

    cout << day.day << endl; 
    cout << day.day ++ << endl;
    cout << day.day << endl;

    system("pause"); 
    return 0;
}

Answer 1

if(day = 365)
{day = 1;}
else
{day ++;}

这不符合你的想法。 =是赋值运算符。 ==将是比较运算符。目前，该表达式将值365分配给day变量，并返回365，执行day = 1;（任何不0的内容都是{{} 1}}）

这是你想要做的：

true

您的代码存在的问题是，虽然您要为该类定义修复后if (day == 365) { day = 1; } else { day++; }，但您在该类的operator++成员上使用此运算符。

在int day中，你不应该int main，你应该做day.day++。

Answer 2

您没有在任何地方调用过载的operator++。

DayOfYear day;
cout << day.day << endl; 
cout << day.day ++ << endl;
cout << day.day << endl;

day.day是day类的成员DayOfYear，因此day.day++只是int的普通增量。你想这样做：

DayOfYear day;
cout << day.day << endl; 
cout << (day++).day << endl;
cout << day.day << endl;

c ++ if语句不能在重载的“++”后缀运算符中工作

2 个答案: