[C++] Operator Overloading 1

Operator overloading literally means overloading the operators.

 

You might have a curiosity about the meaning of operator overloaing.

 

But first, let's see the following code.

 

 

Global

#include <iostream>
using namespace std;

class Point {
private:
    int x, y;
public:
    Point(int _x=0, int _y=0):x(_x), y(_y){}
    void ShowPosition();
    friend Point operator+(const Point& ref1, const Point& ref2);
    /**************************************************************
    friend declare to global function
    (keyword friend is usually used in operator overloading)
    operator+ function can access the private member of Point class
    **************************************************************/
};
void Point::ShowPosition(){
    cout<<x<<" "<<y<<endl;
}

Point operator+(const Point& ref1, const Point& ref2) //global function
{
    Point temp(ref1.x+ref2.x, ref1.y+ref2.y);
    return temp;
}

int main(void)
{
    Point p1(1, 2);
    Point p2(2, 1);

    Point p3 = p1+p2;
    p3.ShowPosition();

    Point p4 = operator+(p1, p2);
    p4.ShowPosition();

    return 0;
}

 

 

Result

3 3
3 3

 

Local

#include <iostream>
using namespace std;
 
class Point {
private:
    int x, y;
public:
    Point(int _x=0, int _y=0):x(_x), y(_y){}
    void ShowPosition() const
    {
        cout<<x<<" "<<y<<endl;
    }
    Point operator+(const Point& ref)             //local function
    {
        Point temp(x+ref.x, y+ref.y);
        return temp;
    }
};
 
int main(void)
{
    Point p1(1, 2);
    Point p2(2, 1);
    
    Point p3 = p1+p2;
    p3.ShowPosition();
    
    p4 = p1.operator+(p2);
    p4.ShowPosition();
 
    return 0;
}

 

 

Impossible to Overload

.  (member access operator)

.*  (pointer-to-member operator)

::  (scope resolution operator)

?:  (ternary operator)

sizeof

typeid

static_cast

dynamic_cast

const_cast

reinterpret_cast

 

 

 

 

 

 

 

 

[참고자료]

- 윤성우의 열혈 C++ 프로그래밍