plS :: Eq a => TraverseKind -> RFactor -> Endom (Skel a)
replS k _r sk =
  case k of
    SeqK -> sk `dotS` sk
    TenK -> sk
    ParK -> sk
    -- ParK -> error "replS ParK impossible"


replS :: Eq a => TraverseKind -> RFactor -> Endom (Skel a)
replS k _r sk =
  case k of
    SeqK -> sk `dotS` sk
    TenK -> sk
    ParK -> sk
    -- ParK -> error "replS ParK impossible"
replS k _r sk =
  case k of
    SeqK -> sk `dotS` sk
    TenK -> sk
    ParK -> sk
    -- ParK -> error "replS ParK impossible"