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Date: Sat, 14 Jun 2003 23:01:53 -0700 (PDT)
From: brogoff@speakeasy.net
To: caml-list@inria.fr
Subject: [Caml-list] Polymorphic variants and signatures
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Hi, 
    I've run into some issues with polymorphic variants that I can't find 
addressed in the manual. I'd like to define a module type which looks 
(simplified) like this

module type CELL_TYPE =
  sig
    type ('a, 'b) t

    val show_rec :
        ('a -> ('b -> string) -> string) -> ([< ('b, 'a) t ] *  'c) inst ->
            ('b -> string) -> string
    ...

  end

and obviously I can't because ('a, 'b) t is not a polymorphic variant type. 

Is there some way I can write such a module type, and, after having written it, 
use it in a functor as follows, 

module Make (Cell : CELL_TYPE) = 
  struct 
    type ('a, 'b) t = [`Newtag of 'b list | ('a, 'b) Cell.t]

    (* and some dispatch on `Newtag and #Cell.t *)
  end

-- 
-- Brian

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