Notation "t @@@ l" := (mapOptionTree (fun t' => t' @@ l) t) (at level 20).
Notation "'<[' a '|-' t ']>'" := (@HaskBrak _ a t).
Notation "t @@@ l" := (mapOptionTree (fun t' => t' @@ l) t) (at level 20).
Notation "'<[' a '|-' t ']>'" := (@HaskBrak _ a t).