非类型模板参数

#ifndef _GAMEBOARD_H
#define _GAMEBOARD_H
#include <iostream>
#include <vector>
template<typename T , size_t WIDTH , size_t HEIGHT>
class GameBoard
{
    public:
        GameBoard();
//        GameBoard(const T& src);    //复制构造函数
//        GameBoard(size_t inWidth,size_t inHeight);
        virtual ~GameBoard();
        
    public:
        void setElemAt(size_t x,size_t y,const T& inElem);
        const T& getElem(size_t x,size_t y);
        size_t getWidth(){return WIDTH;}
        size_t getHeight(){return HEIGHT;}
        static const size_t mDefaultWidth = 10;
        static const size_t mDefaultHeight = 10;        
        
    private:    
        //size_t mWidth,mHeight;
//        void copyFrom(const T& src);
//        void initialContainer();
        T mCells[WIDTH][HEIGHT];
};






#endif //_GAMEBOARD_H

#include "GameBoard.h"

template<typename T , size_t WIDTH , size_t HEIGHT>
GameBoard<T,WIDTH,HEIGHT>::GameBoard()
:mCells()
{
    //initialContainer();
}
template<typename T , size_t WIDTH , size_t HEIGHT>
GameBoard<T,WIDTH,HEIGHT>::~GameBoard()
{
    
}
template<typename T , size_t WIDTH , size_t HEIGHT>
void GameBoard<T,WIDTH,HEIGHT>::setElemAt(size_t x,size_t y,const T& inElem)
{
    mCells[x][y] = inElem;
}
template<typename T , size_t WIDTH , size_t HEIGHT>
const T& GameBoard<T,WIDTH,HEIGHT>::getElem(size_t x,size_t y)
{
    return mCells[x][y];        
}

#include <iostream>
#include <initializer_list>
#include "GameBoard.h"
#include "GameBoard.cpp"
/* run this program using the console pauser or add your own getch, system("pause") or input loop */

constexpr size_t constexprHeight(){return 10;}
int main(int argc, char** argv) 
{GameBoard<int,10,10> myGameBoard;
    GameBoard<int , 10, 10>myAnotherGameBoard;
    myGameBoard.setElemAt(2,3,12);
    myAnotherGameBoard = myGameBoard;
    std::cout << myAnotherGameBoard.getElem(2,3) << std::endl;
    
    int height = 10;
    const int constHeight = 10;
    
    //GameBoard<int,10,height> myGameBoard1;    //error
    GameBoard<int,10,constHeight> myGameBoard1;    //work
    GameBoard<int,10,constexprHeight()> myGameBoard2;//work
    return 0;
}