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Date: Sat, 9 Aug 2008 09:08:59 -0700 (PDT)
From: Dario Teixeira <darioteixeira@yahoo.com>
Subject: Re: [Caml-list] Private and type constraints
To: caml-list@yquem.inria.fr
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X-Spam: no; 0.00; semantics:01 foobar:01 cheers:01 foobar:01 sig:01 foo:01 foo:01 val:01 val:01 struct:01 caml-list:01 functions:01 constructor:01 constraint:01 constraint:01 

Hi,

I just noted that there's already a ticket (#4580) related to this problem:
http://caml.inria.fr/mantis/view.php?id=3D4580

My doubts are a) whether the code below will be correct for 3.11 final;
and b) whether its semantics are equivalent to other uses of 'private',
namely that external pattern-matching on Foobar.t values is allowed,
but the construction of new values must be done through the constructor
functions.  Any thoughts?

Thanks in advance for your time!
Cheers,
Dario Teixeira
=20
module Foobar:
sig
  type foo_t=3D [ `A ]
  type bar_t =3D [ `B ]
  type foobar_t =3D [ foo_t | bar_t ]
  type 'a t =3D private 'a constraint 'a =3D [< foobar_t ]
=20
  val make_a: unit -> foo_t t
  val make_b: unit -> bar_t t
end =3D
struct
  type foo_t =3D [ `A ]
  type bar_t =3D [ `B ]
  type foobar_t =3D [ foo_t | bar_t ]
  type 'a t =3D 'a constraint 'a =3D [< foobar_t ]

  let make_a () =3D `A
  let make_b () =3D `B
end
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