自己写了一个matrix的模板类， 但是在重载运算符时，出现问题了。
下面是matrix类：

// matrix.h -- A simple matrix class; #ifndef __MATRIX_H_ #define __MATRIX_H_ #include  #include  #include  #include  #include  #include  #include  #include  using namespace std; template  class matrix { private: vector> data; public: matrix(int nRow = 2, int nCol = 2){ data.resize(nRow); for (int i = 0; i < nRow; i++) { data[i].resize(nCol); } cout << "Default Constructor" << endl; } matrix(matrix & c):data(c.data){ data = c.data; cout << "Copy Constructor" << endl; } matrix(matrix &&c):data(std::move(c.data)){ cout << "Move Constructor" << endl; } matrix operator = (matrix &c); matrix operator = (matrix &&c){ data = move(c.data); cout << "Move Assignment" << endl; return *this; } int row(){ return data.size();} // Get row of the matrix. int col(){ return (row() ? data[0].size() : 0);} // Get col of the matrix. bool is_empty(){return (row() == 0);} // check if the matrix is empty. bool is_square(){return (!is_empty()) && (row() == col());} // check if the matrix is a square matrix. void resize(int nrow, int ncol); // Resize matrix void display(); // print matrix. T &operator()(int i, int j){ if ((i < 0) || (i >= row())||(j < 0)||(j >=col())) { cerr << "(" << i << "," << j << ") Out of Range" << endl; exit(1); } return data[i][j]; } matrix operator + (matrix &c); matrix operator - (matrix &c); matrix operator * (matrix &c); matrix operator / (matrix &c); matrix operator += (matrix &c); matrix operator -= (matrix &c); matrix operator *= (matrix &c); matrix operator /= (matrix &c); matrix operator + (matrix &&c); matrix operator - (matrix &&c); matrix operator * (matrix &&c); matrix operator / (matrix &&c); matrix operator += (matrix &&c); matrix operator -= (matrix &&c); matrix operator *= (matrix &&c); matrix operator /= (matrix &&c); template friend std::ostream &operator<< (std::ostream &out, matrix &c); ~matrix(){ cout << "Free done" << endl; } }; template  matrix matrix:: operator = (matrix &c){ if (this == &c) { return *this; } if( row() != c.row()){ int nrow = row();data.resize(c.row()); if ((row() < c.row()) && (col() != c.col())) { for (int i = 0; i < c.row(); i++) { data[i].resize(c.col()); } } if ((row() < c.row()) && (col() == c.col())) { for (int i = row(); i < c.row(); i++) { data[i].resize(c.col()); } } } for (int i = 0; i < c.row(); i++) { for (int j = 0; j < c.col(); j++) { data[i][j] = c.data[i][j]; } } cout << "Copy Assignment" << endl; return *this; } template  void matrix:: resize(int nrow, int ncol){ if ((row() == nrow) && (col() == ncol)) { return; } if ((row() == nrow) && (col() != ncol)) { for (int i = 0; i < nrow; i++) { data[i].resize(ncol); } } if ((row() != nrow) && (col() == ncol)) { data.resize(nrow); if (row() < nrow) { for (int i = row(); i < nrow; i++) { data[i].resize(ncol); } } } if ((row() != nrow) && (col() != ncol)) { data.resize(nrow); for (int i = 0; i < nrow; i++) { data[i].resize(ncol); } } } template  void matrix:: display(){ cout << "Row = " << row() << "\tCol = " << col() << endl; cout.precision(10); for (int i = 0; i < row(); i++) { for (int j = 0; j < col(); j++) { cout << setw(8) << data[i][j] << " "; } cout << endl; } } template  matrix matrix:: operator + (matrix &c){ if ((row() != c.row()) || (col() != c.col())) { cerr << "Dimensions of matrices besides + don't match! Exit!!!" << endl; exit(-1); } matrix temp(c.row(),c.col()); for (int i = 0; i < c.row(); i++) { for (int j = 0; j < c.col(); j++) { temp(i,j) = data[i][j] + c(i,j); } } cout << "Copy Add" << endl; return temp; } template  matrix matrix:: operator + (matrix &&c){ if ((row() != c.row()) || (col() != c.col())) { cerr << "Dimensions of matrices besides + don't match! Exit!!!" << endl; exit(-1); } // matrix temp(c.row(),c.col()); for (int i = 0; i < c.row(); i++) { for (int j = 0; j < c.col(); j++) { c(i,j) += data[i][j]; } } cout << "Move Add" << endl; return c; } template  matrix matrix:: operator - (matrix &c){ if ((row() != c.row()) || (col() != c.col())) { cerr << "Dimensions of matrices besides + don't match! Exit!!!" << endl; exit(-1); } matrix temp(row(),col()); for (int i = 0; i < row(); i++) { for (int j = 0; j < col(); j++) { temp(i,j) = data[i][j] - c(i,j); } } return temp; } template  matrix matrix:: operator - (matrix &&c){ if ((row() != c.row()) || (col() != c.col())) { cerr << "Dimensions of matrices besides + don't match! Exit!!!" << endl; exit(-1); } for (int i = 0; i < row(); i++) { for (int j = 0; j < col(); j++) { c(i,j) = data[i][j] - c(i,j); } } return c; } template  std::ostream &operator << (std::ostream &out, matrix &c){ if(c.is_empty()){ return out; } for (int i = 0; i < c.row(); i++) { for (int j = 0; j < c.col(); j++) { out << setw(8) << c(i,j) << " "; } out << endl; } return out; } #endif /* __MATRIX_H_ */

但在调用时，

#include  #include "matrix.h" using namespace std; int main(int argc, const char *argv[]) { matrix my(3,3); my(2,2) = 2.12; cout << my; cout << endl << endl; matrix aaa(my); cout << endl << endl; matrix bbb(my); cout << endl << endl; bbb = aaa + my + bbb; cout << endl << endl; matrix ccc = aaa + my + bbb; cout << endl << endl << endl; matrix ddd=aaa; ddd = bbb; cout << endl << endl; matrix eee(aaa + bbb); cout << endl << endl; return 0; }

结果却是这样：

Default Constructor 0 0 0 0 0 0 0 0 2.12 Copy Constructor Copy Constructor Default Constructor Copy Add Default Constructor Copy Add Move Assignment Copy Constructor Free done Free done Free done Default Constructor Copy Add Default Constructor Copy Add Free done Copy Constructor Copy Assignment Copy Constructor Free done Default Constructor Copy Add Free done Free done Free done Free done Free done Free done

移动构造函数并没有执行，

matrix eee(aaa + bbb);

这里有两次复制构造，一次复制赋值， 本应该是移动构造的，太奇怪了。还有很多问题，大都与这有关。这是怎么回事呢？