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From: Runhang Li <runhang@posteo.net>
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Date: Tue, 17 Nov 2015 10:14:03 -0800
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Subject: [Caml-list] GADT and weak polymorphism

Hi, camels

Consider the following module:

    module HList =3D struct

      type (_, _) hlist =3D
        | Empty : ('a, 'a) hlist
        | Cons  : 'c * ('a, 'b) hlist -> ('c -> 'a, 'b) hlist

      let cons : type a b c. c -> (a, b) hlist -> (c -> a, b) hlist =3D
        fun h tl -> Cons (h, tl)

      let empty =3D Empty

      let ( **> ) =3D cons

      let l =3D '2' **> "str" **> empty

    end

The type of ``l`` is ``(char -> string -> =E2=80=98_a, =E2=80=98_a) hlist``=
. I would like to know the reason that weak polymorphism shows up here.

Thank you


Kindly,

Runhang