#include <cstring>
#include <iostream>

using std::size_t;

class Mesh2D
{
private:

    double* mesh;
    size_t  rows;
    size_t  columns;

public:

    /* constructor */
    Mesh2D(size_t Nx, size_t Ny){
        rows    = Nx;
        columns = Ny;
        mesh    = new double[Nx*Ny] {};
        std::cout << "Mesh created." << std::endl;
    }

    /* destructor */
    ~Mesh2D()
    {
        delete[] mesh;
        std::cout << "Mesh deleted." << std::endl;
    }

    /* accessors */
    double getrows() const {return rows;}
    double getcolumns() const {return columns;}
    double& operator()(size_t i, size_t j)
    {
        if (i > rows || j > columns){
            throw std::out_of_range("Index exceeds array bounds.");
        }
        return mesh[j + i*columns]; // row major access
    }

	double operator()(size_t i, size_t j) const
    {
        if (i > rows || j > columns){
            throw std::out_of_range("Index exceeds array bounds.");
        }
        return mesh[j + i*columns]; // row major access
    }

    /* copy constructor */
    Mesh2D& operator=(const Mesh2D& rhs) // what is the difference between this line and the following? inline operator=(const Mesh2D& rhs)
    {
        if (rhs.rows != rows || rhs.columns != columns){
            throw std::out_of_range("Assignment cannot be performed, mesh dimensions do not agree.");
        }
        if (&rhs == this) //copying the same object
        	return *this;

//        I want to avoid using a for loop
//        for (int i=0; i<rows*columns; i++){
//            mesh[i] = rhs.mesh[i];
//        }
//      Use this instead
        std::memcpy(mesh, rhs.mesh, rows*columns * sizeof(double)); //however the output is not the expected.
        std::cout << "copied!" << std::endl;
        return *this;
    }

};



void PrintMesh2D(const Mesh2D &mesh){ //why isn't it going to work if I add const? I mean: void PrintMesh2D(const Mesh2D &mesh)

    for (int i=0; i<mesh.getrows(); i++){

        for (int j=0; j<mesh.getcolumns(); j++){

            std::cout << mesh(i,j) << " ";
        }
        std::cout << std::endl;
    }
}

int main()
{

    Mesh2D mesh{3,3};
    Mesh2D newmesh{3,3};

    for (int i=0; i<mesh.getrows(); i++){
        for (int j=0; j<mesh.getcolumns(); j++){
            mesh(i,j) = j + i * mesh.getcolumns();
        }
    }

    newmesh = mesh;
    PrintMesh2D(newmesh);

}