C++中特殊运算符的重载

#include <iostream>
#include <stdio.h>
#include <stdlib.h>

using namespace std;

class Operat
{
    float x;
    float y;
public:
    Operat(float _x = 0,float _y = 0)    
    {
        x = _x;
        y = _y;
    }
    Operat(Operat& that)
    {
        x = that.x;
        y = that.y;
    }
    /*
    Operat operator + (Operat& that) //成员函数+重载
    {
        Operat t;
        t.x = x + that.x;
        t.y = y + that.y;
        return t;
    }
    Operat& operator ++ (void)//成员函数前++重载
    {
        x++;
        y++;
        return *this;
    }
    Operat operator ++ (int)//成员函数后++重载
    {
        Operat t(*this);
        t.x++;
        t.y++;
        return t;
    }*/
    Operat& operator [] (int i)//成员函数[]重载
    {
        return *(this+i);
    }
    Operat& operator -> (void)//成员函数->重载
    {
        return *this;
    }
　

　　　　void show()
　　　　{
　　　　　　printf("x=%f,y=%f\n",x,y);
　　　　}

　　　　//注意：普通函数 在类里加上friend声明成类的友元以后 就可以使用类的成员变量，不然成员变量一般式封装在类里的。外面函数是无法使用的

    friend Operat operator + (Operat& a,Operat& b); //声明友员函数 ，这样外部函数就可以访问类的成员变量 
    friend Operat& operator ++ (Operat& a);
    friend Operat operator ++ (Operat& a,int);
    friend ostream& operator << (ostream& os,Operat& p);
    friend istream& operator >> (istream& is,Operat& p);
    ~Operat(){}
};

void* operator new (unsigned int size)//全局函数new的重载
{
        return malloc(size);
}

Operat operator + (Operat& a,Operat& b)//全局函数+的重载
{
    Operat t(a.x+b.x,a.y+b.y);
    return t;
}

Operat& operator ++ (Operat& a)//全局函数前++的重载
{
    a.x++;
    a.y++;
    return a;
}

Operat operator ++ (Operat& a,int)//全局函数后++的重载
{
    Operat t = a;
    a.x++;
    a.y++;
    return t;
}

ostream& operator << (ostream& os,Operat& p)//全局函数 << 的重载
{
    return os << "x=" << p.x << " " << "y=" << p.y << " ";
}

istream& operator >> (istream& is,Operat& p)//全局函数 >> 的重载
{
    return is >> p.x >> p.y;
}

int main()
{
    Operat a(1,2);
    Operat b(3,4);
    (a++).show();
    a.show();
    cin >> a;
    cout << a << b << endl;
}