[C++] cout object(씨아웃 오브젝트)

#include <iostream>
using namespace std;
 
class A {
    int a;
public:
    A(int a = 1000) { this->a = a; }
    void setA(int a) { this->a = a; }
    const int getA() { return a; }
    friend ostream& operator<<(ostream &cout, const A &aa); //직접 접근 불가해서 friend로 지정
    friend istream& operator>>(istream &cin, A &aa); //값을 읽기만 할 때 const로 지정
                                                     //friend int operator+(const A &aa, const A &bb);
    A& operator=(const A &aa) {
        a = aa.a;
        return *this;
    }
 
    A operator+(const A &aa) {
        A tmp; //tmp는 함수가 끝나면 사라짐
        tmp.a = a + aa.a;
        return  tmp;
    }
};
 
/*
int operator+(const A &aa, const A &bb) {
return aa.a + bb.a;
}
*/
 
ostream& operator<<(ostream &cout, const A &aa) {
    cout << aa.a;
    return cout;
}
 
istream& operator>>(istream &cout, A &bb) {
    cin >> bb.a;
    return cin;
}
 
void main() {
    A aa;
    A bb;
    A cc;
 
    cin >> aa >> bb;
    cc = aa + bb; //입력을 하고 대입
                  //내부 - cc.operator=(aa.operator+(bb))
                  //외부 - operator=(cc, operator+(aa, bb))
 
    cout << aa << endl;
    cout << bb << endl;
    cout << cc << endl;
}