cpp——复合类型——函数——运算符重载

运算符重载

c++引入运算符重载机制目的为了类类型(枚举类型)模仿内置类型运算符操作，因此运算符重载必须确保至少一个参数为类类型(枚举类型)，且必须是对象形式，而非指针(引用)形式：

• 运算符重载机制不能改变运算符的操作数个数
• 运算符重载机制不能改变运算符的优先级
• 运算符重载机制不能改变现有类型(内置类型&复合类型)支持的运算符含义，如果重载两个整型的加运算符，改变两个整型的加运算符含义，则编译系统会混乱不堪
• 运算符重载本质还是函数，只是函数名特别的函数，函数名中包含operator和运算符，因此运算符重载函数返回值可为void，且可重载(运算符重载函数形参个数固定，只能通过形参类型不同重载)

enum运算符重载

enum EPoint5{    ZERO,    ONE,    TWO,    THREE,    FOUR,};EPoint5 operator+(EPoint5 point1, int point2){    int ret = ((int)point1 + point2) % 5;    cout << "operator+(EPoint5, int) = " << ret <<  endl;        switch(ret)    {        case 0:            return ZERO;        case 1:            return ONE;        case 2:            return TWO;        case 3:            return THREE;        case 4:            return FOUR;    }        return ZERO;}EPoint5 operator+(int point1, EPoint5 point2){    int ret = (point1 + (int)point2) % 5;    cout << "operator+(int, EPoint5) = " << ret << endl;        switch(ret)    {        case 0:            return ZERO;        case 1:            return ONE;        case 2:            return TWO;        case 3:            return THREE;        case 4:            return FOUR;    }        return ZERO;}EPoint5 operator+(EPoint5 point1, EPoint5 point2){    int ret = ((int)point1 + (int)point2) % 5;    cout << "operator+(EPoint, EPoint5) = " << ret << endl;        switch(ret)    {        case 0:            return ZERO;        case 1:            return ONE;        case 2:            return TWO;        case 3:            return THREE;        case 4:            return FOUR;    }        return ZERO;}void enum_op_overload(){    EPoint5 point = THREE;    point + 3 + 8;    3 + point + 8;    point + point;    operator+(point, 3);    operator+(3, point);    operator+(point, point);}

output：

operator+(EPoint5, int) = 1operator+(EPoint5, int) = 4operator+(int, EPoint5) = 1operator+(EPoint5, int) = 4operator+(EPoint, EPoint5) = 1operator+(EPoint5, int) = 1operator+(int, EPoint5) = 1operator+(EPoint, EPoint5) = 1

class运算符重载

class CPoint{public:    CPoint(int point) : mPoint(point) {}    public:    int mPoint;};CPoint operator+(CPoint point1, int point2){    int ret = (point1.mPoint + point2) % 5;    cout << "operator+(CPoint, int) = " << ret <<  endl;        return CPoint(ret);}CPoint operator+(int point1, CPoint point2){    int ret = (point1 + point2.mPoint) % 5;    cout << "operator+(int, CPoint) = " << ret << endl;        return CPoint(ret);}CPoint operator+(CPoint point1, CPoint point2){    int ret = (point1.mPoint + point2.mPoint) % 5;    cout << "operator+(CPoint, CPoint) = " << ret << endl;        return CPoint(ret);}void class_op_overload(){    CPoint point(3);    point + 3 + 8;    3 + point + 8;    point + point;    operator+(point, 3);    operator+(3, point);    operator+(point, point);}

output：

operator+(CPoint, int) = 1operator+(CPoint, int) = 4operator+(int, CPoint) = 1operator+(CPoint, int) = 4operator+(CPoint, CPoint) = 1operator+(CPoint, int) = 1operator+(int, CPoint) = 1operator+(CPoint, CPoint) = 1

总结

支持重载的运算符：

算术操作符：+，-，*，/，%

复合算术操作符：

位操作符

复合