【发布时间】：2017-01-31 04:56:45
【问题描述】：
我正在为学校编写一段代码，定义一个具有各种功能的 Time 类，例如添加和设置时间。我现在遇到的问题是重载了“+=”运算符。
Time& Time::operator+=(Time& a) {
*this = a + *this;
return *this;
}
我已经重载了“+”运算符，所以我只是为我的“+=”运算符调用它。
Time operator+(Time a, Time b) {
int sumhr = a.hour + b.hour;
int summin = a.minute + b.minute;
if (summin > 59) {
sumhr += summin / 60;
summin = summin % 60;
}
if (sumhr > 23)
sumhr = sumhr % 24;
return Time(sumhr, summin);
}
Time operator+(Time a, int addminutes) {
Time t = a + Time(addminutes);
return t;
}
Time operator+(Time a, double addhours) {
Time t = a + Time(addhours);
return t;
}
在我的 int main() 中，我使用的是：
Time c(61);
c += 120;
cout << "\tc += 120;\t\t";
cout << "c = " << c << "\n";
这给了我错误。我不确定自己做错了什么，因为我已经用 int 和 double 参数重载了“+”运算符。
有什么办法可以解决这个问题？
这是完整的类定义和声明。我正在创建该类并针对我的教授提供的驱动程序运行它，因此无法更改 int main()。
#include <iostream>
using namespace std;
using std:: cout;
class Time {
private:
int hour;
int minute;
public:
Time();
Time(int min);
Time(int hr, int min);
Time(double hrs);
int minutes();
int hours();
Time& operator+=(Time& a);
void set_minutes(int min);
void set_minutes(double min);
void set_hours(int hr);
void set_hours(double hr);
friend ostream& operator<<(ostream& os, const Time& t);
friend Time operator+(Time a, Time b);
friend Time operator+(Time a, int addminutes);
friend Time operator+(Time a, double addhours);
friend bool operator<(Time a, Time b);
friend bool operator==(Time a, Time b);
friend bool operator>=(Time a, Time b);
friend bool operator!=(Time a, Time b);
};
Time::Time() {
hour = 0;
minute = 0;
}
Time::Time(int min) {
if (min > 59) {
hour = min / 60;
minute = min % 60;
}
else {
hour = 0;
minute = min;
}
}
Time::Time(int hr, int min) {
if (min > 59) {
hour = min / 60;
minute = min % 60;
}
else {
hour = hr;
minute = min;
}
if (hour > 23)
hour = hour % 24;
}
Time::Time(double hrs) {
double fraction = 0;
fraction = hrs - (int)hrs;
minute = fraction * 60;
hour = hrs - fraction;
if (hour > 23)
hour = hour % 24;
}
int Time::minutes() {
return minute;
}
int Time::hours() {
return hour;
}
ostream& operator<<(ostream& os, const Time& t)
{
if (t.minute > 9)
os << t.hour << ":" << t.minute;
else
os << t.hour << ":0" << t.minute;
return os;
}
Time operator+(Time a, Time b) {
int sumhr = a.hour + b.hour;
int summin = a.minute + b.minute;
if (summin > 59) {
sumhr += summin / 60;
summin = summin % 60;
}
if (sumhr > 23)
sumhr = sumhr % 24;
return Time(sumhr, summin);
}
Time operator+(Time a, int addminutes) {
Time t = a + Time(addminutes);
return t;
}
Time operator+(Time a, double addhours) {
Time t = a + Time(addhours);
return t;
}
Time& Time::operator+=(Time& a) {
*this = a + *this;
return *this;
}
bool operator<(Time a, Time b) {
if (a.hour > b.hour)
return false;
else if (a.hour < b.hour)
return true;
else {
if (a.minute > b.minute)
return false;
else if (a.minute == b.minute)
return false;
else
return true;
}
}
bool operator==(Time a, Time b) {
if (a.hour != b.hour)
return false;
else {
if (a.minute != b.minute)
return false;
else
return true;
}
}
bool operator>=(Time a, Time b) {
if (a < b)
return false;
else
return true;
}
bool operator!=(Time a, Time b) {
if (a == b)
return false;
else
return true;
}
void Time::set_minutes(int min) {
minute = min % 60;
if (minute == 60) {
minute = 0;
}
}
void Time::set_minutes(double min) {
minute = (int)min % 60;
double rounding = min = (int)min;
if (rounding >= 0.5) {
minute += 1;
if (minute == 60) {
minute = 0;
}
}
}
void Time::set_hours(int hr) {
hour = hr % 24;
if (hour == 24)
hr = 0;
}
void Time::set_hours(double hr) {
hour = (int)hr % 24;
if (hour == 24)
hr = 0;
}
int main() {
Time a;
Time b(5);
Time c(61);
Time d(47, 59);
Time X(5.0);
Time Y(1.5);
Time Z(25.1);
cout << "Testing constructors:\n";
cout << "\tTime a;\t\t\t";
cout << "a = " << a << "\n";
cout << "\tTime b(" << b.minutes() << ");\t\t";
cout << "b = " << b << "\n";
cout << "\tTime c(61);\t\t";
cout << "c = " << c << "\n";
cout << "\tTime d(47,59);\t\t";
cout << "d = " << d << "\n";
cout << "\tTime X(5.0);\t\t";
cout << "X = " << X << "\n";
cout << "\tTime Y(1.5);\t\t";
cout << "Y = " << Y << "\n";
cout << "\tTime Z(25.1);\t\t";
cout << "Z = " << Z << "\n";
cout << "Testing operator+:\n";
cout << "\te = b + c;\t\te = " << b + c << "\n";
cout << "\tf = d + 2;\t\tf = " << 2 + d << "\n";
cout << "\tg = c + 2.75;\t\tg = " << 2.75 + c << "\n";
cout << "Testing operator+=:\n";
c += 120;
cout << "\tc += 120;\t\t";
cout << "c = " << c << "\n";
c += 1.99166666;
cout << "\tc += 1.99166666;\t";
cout << "c = " << c << "\n";
c += 1.99166667;
cout << "\tc += 1.99166667;\t";
cout << "c = " << c << "\n";
cout << "Testing other member functions:\n";
c.set_minutes(60);
cout << "\tc.set_minutes(60);\t";
cout << "c = " << c << "\n";
c.set_minutes(123.45);
cout << "\tc.set_minutes(123.45);\t";
cout << "c = " << c << "\n";
c.set_minutes(67.89);
cout << "\tc.set_minutes(67.89);\t";
cout << "c = " << c << "\n";
cout << "\tc.set_hours(45);\t";
c.set_hours(45);
cout << "c = " << c << "\n";
cout << "\tc.set_hours(1.9);\t";
c.set_hours(1.9);
cout << "c = " << c << "\n";
cout << "\tc.set_hours(1.9999);\t";
c.set_hours(1.9999);
cout << "c = " << c << "\n";
cout << "Testing comparison operators:\n";
if (b < c)
cout << b << " occurs earlier in the day than " << c << ", ";
if (!(b == c))
cout << "hence b != c.\n";
if (c >= b)
cout << c << " occurs later in the day than " << b << ", ";
if (b != c)
cout << "hence c != b.\n";
return 0;
}
【问题讨论】：
-
好吧，显然你的
main看不到这些额外的+操作符并且不知道它们的存在。你在哪里声明它们？从你贴出来的点点滴滴是不可能弄清楚的。 -
刚刚发布了完整的代码。我将 + 运算符作为朋友运算符，将 += 作为成员运算符。
-
但是在您的代码中，您从未定义过在右侧采用
int的+=运算符。难怪编译器找不到它。要么定义它，要么停止尝试使用它。 -
编译器会在其错误消息中告诉您有什么问题：
operator+=采用Time&，但您给它的是int，但没有转换。 -
我的印象是成员运算符只能带一个参数。由于我试图更新时间 c，因此我使用 Time& 作为参数。我不确定应该将 int 放在我的运算符中的哪个位置。对这个话题真的很陌生。谢谢大家。
标签： c++ class compiler-errors overloading operator-keyword