class Complex
{
int a;
int b;
public:
Complex(int a = 0, int b = 0)
{
this->a = a;
this->b = b;
}
int getA()
{
return a;
}
int getB()
{
return b;
}
friend Complex Add(const Complex& p1, const Complex& p2);
};
Complex Add(const Complex& p1, const Complex& p2)
{
Complex ret;
ret.a = p1.a + p2.a;
ret.b = p1.b + p2.b;
return ret;
}
int main()
{
Complex c1(1, 2);
Complex c2(3, 4);
Complex c3 = Add(c1, c2); // 能实现: c1 + c2
printf("c3.a = %d, c3.b = %d\n", c3.getA(), c3.getB());
return 0;
}
通过operator关键字可以定义特殊的函数:
operator的本质是通过函数重载操作符。
Type operator sign(const Type p1, const Type p2)
{
Type ret;
return ret;
}
sign为系统中预定义的操作符,如 + - * / 等。
#include <stdio.h>
class Complex
{
int a;
int b;
public:
Complex(int a = 0, int b = 0)
{
this->a = a;
this->b = b;
}
int getA()
{
return a;
}
int getB()
{
return b;
}
friend Complex operator + (const Complex& p1, const Complex& p2);
};
Complex operator + (const Complex& p1, const Complex& p2)
{
Complex ret;
ret.a = p1.a + p2.a;
ret.b = p1.b + p2.b;
return ret;
}
int main()
{
Complex c1(1, 2);
Complex c2(3, 4);
Complex c3 = c1 + c2; // operator + ( c1, c2) 仅仅是函数调用
printf("c3.a = %d, c3.b = %d\n", c3.getA(), c3.getB());
return 0;
}
可以将操作符重载函数定义为类的成员函数
比全局操作符重载函数少一个参数(左操作数,隐藏的this指针可以代替左操作数)。
不需要依赖友元就可以完成操作符重载。
编译器优先在成员函数中寻找操作符重载函数。
class Type
{
public:
Type operator sign(const Type& p)
{
Type ret;
return ret; }}
#include <stdio.h>
class Complex
{
int a;
int b;
public:
Complex(int a = 0, int b = 0)
{
this->a = a;
this->b = b;
}
int getA()
{
return a;
}
int getB()
{
return b;
}
Complex operator + (const Complex& p)
{
Complex ret;
printf("Complex operator + (const Complex& p)\n");
ret.a = this->a + p.a;
ret.b = this->b + p.b;
return ret;
}
friend Complex operator + (const Complex& p1, const Complex& p2);
};
Complex operator + (const Complex& p1, const Complex& p2)
{
Complex ret;
printf("Complex operator + (const Complex& p1, const Complex& p2)\n");
ret.a = p1.a + p2.a;
ret.b = p1.b + p2.b;
return ret;
}
int main()
{
Complex c1(1, 2);
Complex c2(3, 4);
Complex c3 = c1 + c2; // c1.operator + (c2)
printf("c3.a = %d, c3.b = %d\n", c3.getA(), c3.getB());
return 0;
}
首先调用的是成员函数的版本。
操作符重载的本质是通过函数扩展操作符的功能。全局函数和成员函数都可以实现对操作符的重载。