Matrix(const Matrix<T>& other) {
        elem = make_unique<T[other.numRows*other.numColumns]>;
        numRows = other.numRows;
        numColumns = other.numColumns;

        for (int i = 0; i!=numRows; ++i)
            for (int j = 0; j!=numColumns; ++j)
                elem[i*numColumns + j] = other.elem[i*numColumns + j];

        return *this;

    }