Re: [Caml-list] recursive types and modules problem

[Jacques Garrigue <garrigue@math.nagoya-u.ac.jp>]

2013/11/01 5:13、Nicolas Ojeda Bar <N.Ojeda.Bar@dpmms.cam.ac.uk> のメール：

> What is the best way to rewrite the following recursive definitions so that
> I can actually compile them?
> 
> S = Set.Make (struct type t = t1 let compare x1 x2 = x1.stamp - x2.stamp end)
> 
> type t1 = {
>  stamp : int;
>  x : t2
> }
> 
> and t2 = {
>  y : S.t
> }

A slightly shorter version, using the fact that recursive modules containing only
types require no implementation:

module rec T : sig
  type t1 = { stamp: int; x: t2 }
  and t2 = { y: S.t }
end = T
and S : Set.S with type elt = T.t1 =
  Set.Make
    (struct open T type t = t1 let compare x1 x2 = x1.stamp - x2.stamp end)

Jacques Garrigue