【c++】cout重载能不能写成成员函数，若能，写出函数原型，若不能，说明原因

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// cout重载能不能写成成员函数，若能，写出函数原型，若不能，说明原因#include <iostream>using namespace std;// cout做友元class A;ostream& operator<<(ostream &out, const A &a);class A{friend ostream& operator<<(ostream &out, const A &a);public:A(int n = 0):m(n){}private:int m;};ostream& operator<<(ostream &out, const A &a){out << a.m;return out;}int main(){A a;cout << a << endl;return 0;}// cout并不是不可以做成员函数，但是它的输出形式并不符合大家的习惯，所以还是不要把它写到成员函数里比较好#include <iostream>using namespace std;class A{public:A(int n = 0) :m(n){}// cout做成员函数ostream& operator<<(ostream &out){out << m;return out;}private:int m;};int main(){A a;//注意输出格式a << cout << endl;return 0;}

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