spacepaste

code.ml

open Batteries
module type N = sig
type t
val make: unit -> t
val add_to_self: t -> t -> unit
val as_float: t -> float
end
module Int: N = struct
type t = int ref
let make () = ref 1
let add_to_self x y = x := !x + !y
let as_float = (!) |- float_of_int
end
module Float: N = struct
type t = float ref
let make () = ref 0.5
let add_to_self x y = x := !x +. !y
let as_float = (!) |- identity
end
let which_module = function
| "float" -> (module Float: N)
| "int" -> (module Int: N)
| _ -> invalid_arg "which_module"
let parse: string -> (module N with type t = 'a) * 'a = fun (type a) s ->
let module C = (val (which_module s): N) in
(module C: N), C.make ()

error.txt

File "code.ml", line 30, characters 2-72:
Error: This `let module' expression has type (module N) * C.t
In this type, the locally bound module name C escapes its scope
Command exited with code 2.