关于#c++#的问题：计算二维数组相加

Question

哪位能帮我解释一下这个代码哪里出错了！

//重载+，<<,>>运算符，计算二维数组相加。
#include<iostream>
using namespace std;
class Mat
{
public:
    friend Mat operator+(Mat& a, Mat& b);
    friend istream operator>>(istream& in, Mat& a);
    friend ostream operator<<(ostream& cout, Mat& a);
    Mat();
    
private:
    int mat[2][3];
};
Mat::Mat()
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
            mat[i][j] = 0;
}

istream operator>>(istream& in, Mat& m)
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            cin >> m.mat[i][j];
        };
    return cin;
}
ostream operator<<(ostream& cout, Mat& m)
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            cout << m.mat[i][j];
        };
    return cout;
}
Mat operator+(Mat& a, Mat& b)
{
    Mat n;
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            n.mat[i][j] = a.mat[i][j] + b.mat[i][j];
        }
    return n;
}
int main()
{
    Mat a, b, c;
    cin >> a;
    cin >> b;
    cout << "a=" << a;
    cout << "b=" << b;
    c = a + b;
    cout << "c=" << c;
    
    system("pause");
    return 0;
}

Answer 1

在重载输入输出运算符时，应该使用流对象的引用，而不是对象本身。因此，在重载输入和输出运算符时，应该将参数的类型改为istream&和ostream&，并在返回值处返回相应的流对象。
此外，在输出运算符中，应该以空格或换行符分隔每个数字，而不是将它们挤在一起输出。
下面是修改后的代码：

#include<iostream>
using namespace std;

class Mat
{
public:
    friend Mat operator+(Mat& a, Mat& b);
    friend istream& operator>>(istream& in, Mat& a);
    friend ostream& operator<<(ostream& cout, Mat& a);

    Mat();
private:
    int mat[2][3];
};

Mat::Mat()
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
            mat[i][j] = 0;
}

istream& operator>>(istream& in, Mat& m)
{
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            in >> m.mat[i][j];
        };
    return in;
}

ostream& operator<<(ostream& cout, Mat& m)
{
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 3; j++) {
            cout << m.mat[i][j] << " ";
        }
        cout << endl;
    }
    return cout;
}

Mat operator+(Mat& a, Mat& b)
{
    Mat n;
    for (int i = 0; i < 2; i++)
        for (int j = 0; j < 3; j++)
        {
            n.mat[i][j] = a.mat[i][j] + b.mat[i][j];
        }
    return n;
}

int main()
{
    Mat a, b, c;
    cin >> a >> b;
    cout << "a=" << endl << a;
    cout << "b=" << endl << b;
    c = a + b;
    cout << "c=" << endl << c;

    system("pause");
    return 0;
}