c++ operator 关键字详解

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在C++中，operator关键字用于定义和重载运算符，使得自定义类的对象可以使用标准运算符（如 +, -, *, /, ==, != 等）进行操作。通过运算符重载，可以使自定义类的行为类似于内置类型，从而提高代码的可读性和可维护性。

运算符重载的基本语法
运算符重载通过定义一个特殊的成员函数或友元函数来实现，其语法如下：

返回类型 operator 运算符 (参数列表);

例如，重载 + 运算符：

class Complex {
public:double real, imag;Complex(double r, double i) : real(r), imag(i) {}// 重载 + 运算符Complex operator+(const Complex& other) const {return Complex(real + other.real, imag + other.imag);}
};

重载常见运算符的示例

重载加法运算符 (+)：

#include <iostream>
using namespace std;class Complex {
public:double real, imag;Complex(double r = 0, double i = 0) : real(r), imag(i) {}// 重载 + 运算符Complex operator+(const Complex& other) const {return Complex(real + other.real, imag + other.imag);}void print() const {cout << "(" << real << ", " << imag << ")" << endl;}
};int main() {Complex c1(3.0, 4.0);Complex c2(1.0, 2.0);Complex c3 = c1 + c2; // 使用重载的 + 运算符c3.print();           // 输出: (4, 6)return 0;
}

重载等于运算符 (==)：

#include <iostream>
using namespace std;class Complex {
public:double real, imag;Complex(double r = 0, double i = 0) : real(r), imag(i) {}// 重载 == 运算符bool operator==(const Complex& other) const {return (real == other.real) && (imag == other.imag);}
};int main() {Complex c1(3.0, 4.0);Complex c2(3.0, 4.0);Complex c3(1.0, 2.0);if (c1 == c2) {cout << "c1 and c2 are equal." << endl; // 输出: c1 and c2 are equal.} else {cout << "c1 and c2 are not equal." << endl;}if (c1 == c3) {cout << "c1 and c3 are equal." << endl;} else {cout << "c1 and c3 are not equal." << endl; // 输出: c1 and c3 are not equal.}return 0;
}

重载插入运算符 (<<)：

插入运算符通常重载为友元函数，以便可以访问私有成员。

#include <iostream>
using namespace std;
class Complex {
public:double real, imag;Complex(double r = 0, double i = 0) : real(r), imag(i) {}// 声明友元函数来重载 << 运算符friend ostream& operator<<(ostream& os, const Complex& c);
};
// 定义友元函数来重载 << 运算符
ostream& operator<<(ostream& os, const Complex& c) {os << "(" << c.real << ", " << c.imag << ")";return os;
}
int main() {Complex c1(3.0, 4.0);cout << c1 << endl; // 输出: (3, 4)return 0;
}