重载流插入运算符《和流提取运算符》 第五题

#include <iostream.h> //using namespace std; class Matrix  {public:    Matrix();    friend Matrix operator+(Matrix &,Matrix &);    friend ostream& operator<<(ostream&,Matrix&);    friend istream& operator>>(istream&,Matrix&);   private:    int mat[2][3];  };   Matrix::Matrix() {for(int i=0;i<2;i++)   for(int j=0;j<3;j++)    mat[i][j]=0; }  Matrix operator+(Matrix &a,Matrix &b) {Matrix c;  for(int i=0;i<2;i++)    for(int j=0;j<3;j++)      {c.mat[i][j]=a.mat[i][j]+b.mat[i][j];      }  return c; }  istream& operator>>(istream &in,Matrix &m) {cout<<"input value of matrix:"<<endl;  for(int i=0;i<2;i++)   for(int j=0;j<3;j++)    in>>m.mat[i][j];  return in; }  ostream& operator<<(ostream &out,Matrix &m) {for (int i=0;i<2;i++)   {for(int j=0;j<3;j++)    {out<<m.mat[i][j]<<" ";}     out<<endl;}  return out; }  int main() { Matrix a,b,c;  cin>>a;  cin>>b;  cout<<endl<<"Matrix a:"<<endl<<a<<endl;  cout<<endl<<"Matrix b:"<<endl<<b<<endl;  c=a+b;  cout<<endl<<"Matrix c = Matrix a + Matrix b :"<<endl<<c<<endl;  return 0; }