I am trying to define a matrix class with simple operations. To be compitable with int, float, double data type, I use the template. And I overload the "<<" operator to print the matrix. How ever, when I compile the program, I get a LNK2019 error.
Error 2 error LNK1120: 1 unresolved externals
Error 1 error LNK2019: unresolved external symbol "class std::basic_ostream > & __cdecl operator<<(class std::basic_ostream > &,class Mat const &)" (??6@YAAAV?$basic_ostream@DU?$char_traits@D@std@@@std@@AAV01@ABV?$Mat@H@@@Z) referenced in function _main
I have tried to find the error and just could not figure out the problem.
Here is the detail: system infromation: windows 10 x64, visual studio 2013
mat.h file
#ifndef _MAT_H_
#define _MAT_H_
#include <iostream>
#include <ostream>
#include <sstream>
#include <vector>
#include <cstring>
#include <cassert>
//implement Mat class in c++
template<typename T>
class Mat{
friend std::ostream& operator<<(std::ostream &os, const Mat<T> &m);
friend std::istream& operator>>(std::istream &is, Mat<T> &m);
public:
//construct
Mat();
Mat(size_t i, size_t j);
//destructor
~Mat();
//access element value
T& MatVale(size_t i, size_t j);
const T& MatVale(size_t i, size_t j) const;
//get row and col number
const size_t rows() const{ return row; }
const size_t cols() const{ return col; }
private:
size_t row;
size_t col;
T* pdata;
};
#endif
mat.cpp file
`
#include "mat.h"
using std::cout;
using std::endl;
using std::istream;
using std::ostream;
template<typename T>
ostream& operator<<(ostream &os, const Mat<T>&m){
for (int i = 0; i < m.row; i++){
for (int j = 0; j < m.col; j++){
os << m.pdata[i*m.col + j] << " ";
}
os << std::endl;
}
os << std::endl;
return os;
}
template<typename T>
istream& operator>>(istream &is, Mat<T>&m){
for (int i = 0; i < m.row; i++){
for (int j = 0; j < m.col; j++){
is >> m.pdata[i*m.col + j];
}
}
return is;
}
//construct
template<typename T>
Mat<T>::Mat(){
cout << "defalut constructor" << endl;
row = 0;
col = 0;
pdata = 0;
}
template<typename T>
Mat<T>::Mat(size_t i, size_t j){
row = i; col = j;
pdata = new T[row*col];
std::memset(pdata, 0, row*col*sizeof(T));
}
//destructor
template<typename T>
Mat<T>::~Mat(){
if (pdata) delete[] pdata;
}
//access element value
template<typename T>
inline T& Mat<T>::MatVale(size_t i, size_t j){
assert(pdata && i>=0 && j>=0 && i < row && j < col);
return pdata[i*col + j];
}
template<typename T>
inline const T& Mat<T>::MatVale(size_t i, size_t j) const{
assert(pdata && i >= 0 && j >= 0 && i < row && j < col);
return pdata[i*col + j];
}
int main(){
Mat<int> mat1(7, 2);
Mat<int> mat2(7, 2);
for (size_t i = 0; i < mat1.rows(); i++){
for (size_t j = 0; j < mat1.cols(); j++){
mat1.MatVale(i, j) = i + j+3;
mat2.MatVale(i, j) = 2 * i + j+11;
}
}
std::cout << mat1;//comment this line then it is okay.
return 1;
}