type t

type axe =
  | Horizontal of int
  | Vertical of int
  | Cell of (int * int)

(** Create a new selection from a cell *)
val create: (int * int) -> t

val is_selected: axe -> t -> bool

(** Get the selection origin *)
val extract: t -> (int * int)

val shift: t -> (int * int) -> (int * int)

val fold: ('a -> int * int -> 'a) -> 'a -> t -> 'a

val extends:  Actions.direction -> t -> t