Module Xform

module Xform : sig..end

Maps the empty list to None, and all the others lists to Some

type error =  | NoError | ErrorNoMsg | ErrorMsg of string

type 'a convert =  | ConvError of string | Converted of 'a

module type Xform = sig..end

module Xform : Xformwith type 'a monad = 'a

module XformLwt : Xformwith type 'a monad = 'a Lwt.t