运算符重载

操作符重载

• C++不允许用户自己定义新的运算符,只能对已有的 C++运算符进行重载

  
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• 运算符重载函数可以是类的成员函数,也可以是类的友元函数,还可以是既非
  类 的成员函数也不是友元函数的普通函数

操作符重载基本语法

#include <iostream>

using namespace std;

class Complex {
    private:
        int m_a;
        int m_b;
    public:
        Complex(int a, int b) {
            m_a = a;
            m_b = b;
        }
        void printComplex() {
            cout << "( m_a = "<< m_a << ", m_b = " << m_b << "i)" << endl;
        }

        Complex operator-(Complex& c1) {
            Complex tmp(this->m_a - c1.m_a, this->m_b - c1.m_b);
            return tmp;
        }

        friend Complex operator+(Complex& com1, Complex& com2);
};

//操作符重载写在全局  operator和要重载的操作符中间不能有空格
Complex operator+(Complex& com1, Complex& com2) {
    Complex tmp(com1.m_a + com2.m_a, com1.m_b + com2.m_b);
    return tmp;
}

int main() {
    Complex c1(1,2);
    Complex c2(2,3);
    c1.printComplex();
    c2.printComplex();

    Complex c3 = c1+c2;
    c3.printComplex();

    Complex c4 = c3 - c2 - c1;
    c4.printComplex();
    return 0;
}

双目运算符重载

#include <iostream>

using namespace std;

class Complex {
    private:
        int m_a;
        int m_b;
    public:
        Complex(int a, int b) {
            m_a = a;
            m_b = b;
        }
        Complex(){}
        void printComplex() {
            cout << "( m_a = "<< m_a << ", m_b = " << m_b << "i)" << endl;
        }

        Complex& operator+=(Complex& c1) {
            this->m_a += c1.m_a;
            this->m_b += c1.m_b;
            return *this;
        }

        Complex& operator++() {
            this->m_a++;
            this->m_b++;
            return *this;
        }

        const Complex& operator++(int) {
            Complex temp(this->m_a, this->m_b);
            this->m_a++;
            this->m_b++;
            return temp;
        }
};

int main() {
    Complex c1(1,2);
    Complex c2(2,3);
    
    (c1 += c2) += c2;
    c1.printComplex();

    Complex c3(5,6);
    ++++c3;
    c3.printComplex();

    Complex c4(3,2);
    c4++;
    c4.printComplex();
    
    return 0;
}

左移右移运算符重载

#include <iostream>

using namespace std;

class Complex {
    private:
        int m_a;
        int m_b;
    public:
        Complex(int a, int b) {
            m_a = a;
            m_b = b;
        }
        friend ostream& operator<<(ostream &os, Complex &c1);
        // 左移操作符，只能写在全局, 不能写在成员方法在，因为调用顺序会变反 c1 << cout;
        // ostream& operator<<(ostream &os){
        //     os <<"( m_a = "<< this->m_a << ", m_b = " << this->m_b << "i)" << endl;
        //     return os;
        // }
        friend istream& operator>>(istream &is, Complex &c1);
};


ostream& operator<<(ostream &os, Complex &c1){
    os <<"( m_a = "<< c1.m_a << ", m_b = " << c1.m_b << "i)";
    return os;
}

istream& operator>>(istream &is, Complex &c1) {
    cout <<" m_a = ";
    is >> c1.m_a;
    cout <<" m_b = ";
    is >> c1.m_b;
    return is;
}

int main() {
    Complex c1(1,2);
    cout << c1 << "    "<< c1 << endl;
    
    cin >> c1;
    cout << c1 << "    "<< c1 << endl;
    return 0;
}

=号操作符重载

#include <iostream>
#include <string.h>

using namespace std;

class Student {
    private:
        int id;
        char * name;
    public:
        Student() {
            this->id = 0;
            this->name = NULL;
        }
        Student(int id, char *name) {
            this->id = id;
            int length = strlen(name);
            this->name = new char[length +1];
            strcpy(this->name, name);
        }

        Student& operator=(const Student &stu) {
            //防止自身赋值
            if (this == &stu)
            {
                return *this;
            }
            // 先将自身的额外开辟的空间回收
            if (this->name != NULL)
            {
                delete this->name;
                this->name = NULL;
                this->id = 0;
            }
            
            //执行深拷贝
            this->id = stu.id;
            int length = strlen(stu.name);
            this->name = new char[length +1];
            strcpy(this->name, stu.name);
        }

        void print() {
            cout<< "id = " << id << "   name = " << name << endl;
        }

        ~Student() {
            if (this->name != NULL)
            {
                delete this->name;
                this->name = NULL;
            }
        }
};

int main() {
    Student stu1(22, "张三丰");
    Student stu2;
    stu2 = stu1;
    stu2.print();
    return 0;
}