type t =
  1. | Start
  2. | End
include Sexplib0.Sexpable.S with type t := t
val t_of_sexp : Sexplib0.Sexp.t -> t
val sexp_of_t : t -> Sexplib0.Sexp.t
include Ppx_compare_lib.Comparable.S with type t := t
val compare : t -> t -> int