sig
type t = string
val string : string -> t
val substring : string -> int -> int -> t
val file : string -> t
val to_hex : t -> string
val from_hex : string -> t
val channel : BatIO.input -> int -> Digest.t
val output : 'a BatIO.output -> t -> unit
val print : 'a BatIO.output -> Digest.t -> unit
val input : BatIO.input -> Digest.t
val compare : t -> t -> int
end