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5天前关闭。
我尝试重载运算符〈〈和++（post和pre）。这是我的代码的一部分，但是我得到错误“e0349：没有与这些操作数”“匹配的运算符。您能告诉我哪里出错了吗？（C++，VS2022）

#include <iostream>
#include <string>

using namespace std;

class K {
    int x, y;
public:
    K(int a, int b) :x(a), y(b) {};
    K() :x(0), y(0) {};
    K operator++(int);
    K& operator++();
    friend ostream& operator<< (ostream & str, K & obj);
    
};

K K::operator++(int) {
    K temp(*this);
    x += 1;
    y += 1;
    return temp;
}
K& K::operator++() {
    x += 1;
    y += 1;
    return *this;
}
ostream& operator<<(ostream& str, K& obj) {
    str << "[" << obj.x << ", " << obj.y << "]";
    return str;
}

int main(int argc, char* argv[])
{
    K obj{10, 20};
    cout << obj++ << endl;  //here I get error
    cout << obj << endl;
    cout << ++obj << endl;

}