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Date: Fri, 10 Jun 2016 22:18:40 +0200
From: =?utf-8?Q?S=C3=A9bastien?= Hinderer <Sebastien.Hinderer@inria.fr>
To: Gabriel Scherer <gabriel.scherer@gmail.com>
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Subject: Re: [Caml-list] Error: The type abbreviation t is cyclic while
 defining submodules

Gabriel Scherer (2016/06/10 16:05 -0400):
> P.S.: Note that "nonrec" is only in definitions (struct .. end) and
> signatures (sig .. end), not in equations such as "with type t = t"
> which are a different construct, interpreted recursively -- not the
> best choice for consistency, but well.

So to make an equality between two types public one has to first
introduce a signature, right?

Now the code looks like this:

type t = float * float

let compare = Pervasives.compare

(* Other functions on points *)

module OrderedPoints : Set.OrderedType with type t = t = struct
  type nonrec t = t
  let compare = compare
end

module PointSet (* : Set.S with type t = t *) = Set.Make(OrderedPoints)

Note the commented bit in the last line, when it is uncommented it does
indeed not work.

Thanks,

Sébastien.