ndarray_oc_pack Subroutine

  subroutine ndarray_oc_pack(this, z, flags)
    class(ndarray_oc), intent(in   ) :: this
    real(pfdp),  intent(  out)       :: z(:)
    integer,     intent(in   ), optional   :: flags
    integer :: which
    
    which = 0
    if (present(flags)) which = flags

    select case (which)
    case (0)
       !z = [sol%yflatarray, sol%pflatarray] 
       !z has to be right size? initialized to nvars, so it can hold either y or p
       !is it ever needed to pack y and p simultaneously?
       stop "ERROR in ndarray_oc_pack: only 1, 2 allowed as flags"
    case (1)
       z = this%yflatarray
    case (2)
       z = this%pflatarray
    case default
       stop "ERROR in ndarray_oc_pack: only 1, 2 allowed as flags"
    end select
  end subroutine ndarray_oc_pack