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From: Mikhail Mandrykin <mandrykin@ispras.ru>
To: Vincent Jacques <vincent@vincent-jacques.net>
Cc: caml-list@inria.fr
Date: Fri, 14 Apr 2017 21:47:09 +0300
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References: <CAEnGa7CottXs1fTttfwfBtVVPtR4rLtKw+Ok+5Zx=8=F3WgviA@mail.gmail.com> <2493165.Qrs57diDXJ@molnar>
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Subject: Re: [Caml-list] Typing of recursive function with polymorphic
 variants

On =D0=BF=D1=8F=D1=82=D0=BD=D0=B8=D1=86=D0=B0, 14 =D0=B0=D0=BF=D1=80=D0=B5=
=D0=BB=D1=8F 2017 =D0=B3. 21:11:52 MSK Mikhail Mandrykin wrote:
> the desired type ([< `A of 'a | `B ] as 'a) -> [> `B]
> val f2 :                 ([< `A of 'a | `B ] as 'a) -> [ `B ] =3D <fun>
Actually, one more polymorphic variable:
let rec f2 : 'a 'b. ([<`A of 'a | `B ] as 'a) -> ([>`B] as 'b)=3D function
  | `A x -> f2 (f2 x)
  | `B -> `B;;
val f2 : ([< `A of 'a | `B ] as 'a) -> [> `B ] =3D <fun>

--=20
Mikhail