From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <goswin-v-b@web.de>
Received: from mail3-relais-sop.national.inria.fr (mail3-relais-sop.national.inria.fr [192.134.164.104])
	by sympa.inria.fr (Postfix) with ESMTPS id 087867FCCB
	for <caml-list@sympa.inria.fr>; Tue, 14 Apr 2015 14:12:48 +0200 (CEST)
Received-SPF: None (mail3-smtp-sop.national.inria.fr: no sender
  authenticity information available from domain of
  goswin-v-b@web.de) identity=pra; client-ip=212.227.15.3;
  receiver=mail3-smtp-sop.national.inria.fr;
  envelope-from="goswin-v-b@web.de";
  x-sender="goswin-v-b@web.de"; x-conformance=sidf_compatible
Received-SPF: Pass (mail3-smtp-sop.national.inria.fr: domain of
  goswin-v-b@web.de designates 212.227.15.3 as permitted
  sender) identity=mailfrom; client-ip=212.227.15.3;
  receiver=mail3-smtp-sop.national.inria.fr;
  envelope-from="goswin-v-b@web.de";
  x-sender="goswin-v-b@web.de"; x-conformance=sidf_compatible;
  x-record-type="v=spf1"
Received-SPF: None (mail3-smtp-sop.national.inria.fr: no sender
  authenticity information available from domain of
  postmaster@mout.web.de) identity=helo;
  client-ip=212.227.15.3;
  receiver=mail3-smtp-sop.national.inria.fr;
  envelope-from="goswin-v-b@web.de";
  x-sender="postmaster@mout.web.de";
  x-conformance=sidf_compatible
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: A0AyAQBTAy1VnAMP49Rc0XACgT48EAEBAQEBAQERAQEBAQEGDQkJFC6EIAEBBDIBVgsYCSUPBSiISQEYxRYfhXcBCyCLK4UDFoMBgRYBBJsehwoMjVeCJB2BUoMwAQEB
X-IPAS-Result: A0AyAQBTAy1VnAMP49Rc0XACgT48EAEBAQEBAQERAQEBAQEGDQkJFC6EIAEBBDIBVgsYCSUPBSiISQEYxRYfhXcBCyCLK4UDFoMBgRYBBJsehwoMjVeCJB2BUoMwAQEB
X-IronPort-AV: E=Sophos;i="5.11,576,1422918000"; 
   d="scan'208";a="111013960"
Received: from mout.web.de ([212.227.15.3])
  by mail3-smtp-sop.national.inria.fr with ESMTP/TLS/DHE-RSA-AES256-SHA; 14 Apr 2015 14:12:47 +0200
Received: from frosties.localnet ([95.208.221.151]) by smtp.web.de (mrweb002)
 with ESMTPSA (Nemesis) id 0Lxx4O-1ZTXsA2oLc-015K33 for <caml-list@inria.fr>;
 Tue, 14 Apr 2015 14:12:46 +0200
Received: from mrvn by frosties.localnet with local (Exim 4.84)
	(envelope-from <goswin-v-b@web.de>)
	id 1Yhzht-0004dU-KT
	for caml-list@inria.fr; Tue, 14 Apr 2015 14:12:45 +0200
Date: Tue, 14 Apr 2015 14:12:45 +0200
From: Goswin von Brederlow <goswin-v-b@web.de>
To: caml-list@inria.fr
Message-ID: <20150414121245.GA16590@frosties>
References: <20150209142107.GA24464@pl-59055.rocqadm.inria.fr>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20150209142107.GA24464@pl-59055.rocqadm.inria.fr>
User-Agent: Mutt/1.5.23 (2014-03-12)
X-Provags-ID:  V03:K0:bRO+oIVebP7FkY2sYenrgicqOYbJaqz8CF6QKoPVf1ck9AtEtmG
 fYuxpVsyx6jmuLLGknb/jLJFtlMJTSXETT8+Y9hMOfyh0Y7JPCWYD0WOERcjdvG2RWnTEoO
 RZ1ZHY/mn7psZYuGD3Xfe/oTjNefXHrmBFWmM3DrgQvS4IefPQ1/nURw7TazCytFnWiFGhR
 U83gxwTTJsnWBcveAQgvg==
X-UI-Out-Filterresults: notjunk:1;
Subject: Re: [Caml-list] Polymorphic hash tables

On Mon, Feb 09, 2015 at 03:21:07PM +0100, Sébastien Hinderer wrote:
> Hi,
> 
> Is there a way to just replace OCaml's standard hash function for some
> tables?
> 
> Here is an example:
> 
> module MyHashedType : Hashtbl.HashedType = struct
>   type t
>   let my_n = 20
>   let my_m = 30
>   let equal = (=)
>   let hash = Hashtbl.hash_param my_n my_m
> end
> 
> module MyHashtbl = Hashtbl.Make(MyHashedType)
> 
> let (mytbl : int MyHashtbl.t) = MyHashtbl.create 100
> 
> With this example polymorphism seems to be lost and the compiler does
> not accept something like
> type t = 'a
> to retrieve a generic type as for the standard hash tables.
> 
> Any suggestion?
> 
> Thanks a lot.
> Sébastien.

You have to use a functor there.

MfG
	Goswin