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From: Ivan Gotovchits <ivg@ieee.org>
To: Jacques Garrigue <garrigue@math.nagoya-u.ac.jp>
Cc: OCaML List Mailing <caml-list@inria.fr>
References: <00C57DF0-C6F0-4EDE-8607-2155F3A17146@math.nagoya-u.ac.jp>
Date: Mon, 29 Apr 2013 07:45:36 +0400
In-Reply-To: <00C57DF0-C6F0-4EDE-8607-2155F3A17146@math.nagoya-u.ac.jp>
	(Jacques Garrigue's message of "Sun, 28 Apr 2013 09:02:56 +0900")
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Subject: Re: [Caml-list] Request for feedback: A problem with injectivity
 and GADTs

Jacques Garrigue <garrigue@math.nagoya-u.ac.jp> writes:
>
> If we need to be able to define GADTs relying on the injectivity of some =
abstract
> types, a straightforward solution is to add injectivity annotations on ty=
pe parameters,
> the same way it was done for variance:
>
>   type #'a t
>

I'm not sure that symbol '#' is a good choice. It is already used for
open types and may impose difficulties in undestanding code (and
compiler messages) when overriden. For me '#' is something polymorphic
and related to OOP.=20

And indeed, =C2=AB#'a=C2=BB is to perlish... Personally, I would prefer som=
ething
like:

  type 'a t
  constraint 'a is injective


P.S. the following symbols looks more =C2=ABinjective=C2=BB for me: '>', '^=
', '=3D',
though the last one can be confused with the invariance.



--=20
         (__)=20
         (oo)=20
   /------\/=20
  / |    ||=20=20=20
 *  /\---/\=20
    ~~   ~~=20=20=20
...."Have you mooed today?"...