运算符重载

运算符重载本质

重新定义运算符的操作，返回自定义的结果。

对于A operator sign (B res1 , C res2)
B类型的res1和C类型的res2，进行sign操作，返回一个类型是A的结果。

1. 一元运算符重载

(1)重载++

class student
{
    public:
        int a;
        student(int a)
        {
            this->a = a;
        }
        student operator ++  ()
        {
            ++a;
            return student(a);
        }
};

int main()
{
    student a(3);
    ++a;
    cout<<a.a;
    return 0;
}

(2)重载-(负号)

class student
{
    public:
        int a;
        student(int a)
        {
            this->a = a;
        }
        student operator -  ()
        {
            return student(-a);
        }
};

int main()
{
    student a(3);
    cout<<-a.a;
    return 0;
}

2. 二元运算符重载(+)

class student
{
    public:
        int a;
        student(int a)
        {
            this->a = a;
        }
        student operator + (student res)
        {
            return student(a+res.a);
        }
};

int main()
{
    student res1(3),res2(4);
    cout<<(res1+res2).a;
    return 0;
}

3. 关系运算符重载(<)

struct student
{
    int a;
    bool operator <  (student x)
    {
        return a<x.a;
    }
};

4. 输入输出运算符重载

class student
{
    public:
        int a,b;
//         student(int a,int b)
//         {
//             this->a = a;this->b = b;
//         }
        friend ostream &operator << (ostream &output,student &s)
        {
            output<<s.a<<" "<<s.b;
            return output;
        }
        friend istream &operator >> (istream &input , student &s)
        {
            input>>s.a>>s.b;
            return input;
        }
};

int main()
{
    student a;
    cin>>a;
    cout<<a;
    return 0;
}

5. 赋值运算符重载(=)

class student
{
    public:
        int a,b;
        student(int a,int b)
        {
            this->a = a;this->b = b;
        }
        
        void operator = (student res)
        {
            a = res.a;b = res.b;
        }
};

int main()
{
    student a(3,2),b(2,3);
    a = b;
    cout<<a.a<<" "<<a.b;
    return 0;
}

6. 下标运算符重载

class student
{
    public:
        int a,b;
        int arr[100];
        student(int a,int b)
        {
            this->a = a;this->b = b;
        }
        int operator [] (int i)
        {
            return arr[i];
        }
};

int main()
{
    student a(3,2);
    a.arr[3] = 2;
    cout<<a[3];
    return 0;
}