addVec Subroutine

    subroutine addVec(this, k, vec)
        type(LanczosCalcType), intent(inout) :: this
        integer, intent(in) :: k
        HElement_t(dp), intent(in) :: vec(:)
        if (this%super%t_store_subspace_basis) then
            this%super%basis_vectors(:, k) = vec
        else
            this%old_v = this%current_v
            if (k == 2) this%first_v = this%current_v
            this%current_v = vec
        end if
    end subroutine addVec