尝试过载输出运算符时出错

我正在学习C++，但在构建项目时遇到了链接错误。

该错误与我的代码重载输出<<运算符有关。

这是我收到的错误：

1>lab4.obj : error LNK2019: unresolved external symbol "class std::basic_ostream<char,struct std::char_traits<char> > & __cdecl operator<<(class std::basic_ostream<char,struct std::char_traits<char> > &,class Matrix<2,2> const &)" (??6@YAAAV?$basic_ostream@DU?$char_traits@D@std@@@std@@AAV01@ABV?$Matrix@$01$01@@@Z) referenced in function _main
1>c:usersmattdocumentsvisual studio 2010Projectslab4Debuglab4.exe : fatal error LNK1120: 1 unresolved externals

如何修复此错误？我在下面附上了我的代码

#include <iostream>
#include <string>
#include <stdio.h>
using namespace std;
template <int m, int n> 
class Matrix{
public:
    int data[m][n];
public:
    Matrix(){};
    void setup(){
        for(int i=0;i<m;i++){
            for(int j=0;j<n;j++){
                data[i][j] = 0;
            }
        }
    }
    void setAll(int integer){
        for(int i=0;i<m;i++){
            for(int j=0;j<n;j++){
                data[i][j] = integer;
            }
        }
    }
    void output(){
        for(int i=0;i<m;i++){
            cout << "[ ";
            for(int j=0;j<n;j++){
                cout << data[i][j] << " ";
            }
            cout<<"]"<<endl;
        }
    }
    Matrix<m,n> operator+ (const Matrix<m,n> &rhs)
    {
        Matrix<m,n> result;
        for(int i=0;i<m;i++){
            for(int j=0;j<n;j++){
                result.data[i][j] = this->data[i][j] + rhs.data[i][j];
            }
        }
        return result;
    }
    Matrix<m,n> operator- (const Matrix<m,n> &rhs)
    {
        Matrix<m,n> result;
        for(int i=0;i<m;i++){
            for(int j=0;j<n;j++){
                result.data[i][j] = this->data[i][j] - rhs.data[i][j];
            }
        }
        return result;
    }
    template <int l>
    Matrix <m,l> operator*(const Matrix<n,l> &rhs) //const
    {
        //only if number of columns in the first matrix equals the number of rows in the second matrix. 
        Matrix<m,l> result;
        for(int i = 0; i < m; i++){
            for(int j = 0 ; j < l ; j++){
                result.data[i][j] = 0;
                for(int k = 0; k < n; k++){
                    result.data[i][j] += this->data[i][k] * rhs.data[k][j];
                }
            }
        }
        return result;
    };
    Matrix <m,n> operator*(int scalar){
        Matrix <m,n> result;
        for(int i= 0; i < m; i++){
            for(int j = 0; j < n; j++){
                result.data[i][j] = this->data[i][j] * scalar;
            }
        }
        return result;
    };
    friend ostream& operator<<(ostream &os, const Matrix<m,n> &rhs);
    friend Matrix <m,n> operator++(const Matrix<m,n> &rhs, int);
    friend Matrix <m,n> operator--(const Matrix<m,n> &rhs, int);
};
template <int m, int n> 
ostream& operator<< (ostream &os, const Matrix<m,n> &rhs){
    for(int i=0;i<m;i++){
        os << "[ ";
        for(int j=0;j<n;j++){
            os << rhs.data[i][j] << " ";
        }
        os<<"]"<<endl;
    }
    return os;
}
template <int m, int n> 
 Matrix <m,n> operator++(const Matrix<m,n> &rhs, int){
    for(int i=0;i<m;i++){
        for(int j=0;j<n;j++){
            rhs.data[i][j]++;
        }
    }
}
template <int m, int n> 
 Matrix <m,n> operator--(const Matrix<m,n> &rhs, int){
    for(int i=0;i<m;i++){
        for(int j=0;j<n;j++){
            rhs.data[i][j]--;
        }
    }
}
int main(){
    Matrix<2,2> m = Matrix<2,2>();
    m.setup();
    //m.output();
    Matrix<2,2> p = Matrix<2,2>();
    p.setup();
    Matrix<2,2> z = Matrix<2,2>();
    z = m + p;
    //z.output();
    z = z * z;
    cout << z;
    string stopper;
    getline(cin, stopper);
}