From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <5764c029b688c1c0d24a2e97cd764f@gmail.com>
X-Original-To: caml-list@sympa.inria.fr
Delivered-To: caml-list@sympa.inria.fr
Received: from mail2-relais-roc.national.inria.fr (mail2-relais-roc.national.inria.fr [192.134.164.83])
	by sympa.inria.fr (Postfix) with ESMTPS id 31B5D7EE49
	for <caml-list@sympa.inria.fr>; Fri, 22 Feb 2013 21:13:43 +0100 (CET)
Received-SPF: None (mail2-smtp-roc.national.inria.fr: no sender
  authenticity information available from domain of
  5764c029b688c1c0d24a2e97cd764f@gmail.com) identity=pra;
  client-ip=74.125.82.50;
  receiver=mail2-smtp-roc.national.inria.fr;
  envelope-from="5764c029b688c1c0d24a2e97cd764f@gmail.com";
  x-sender="5764c029b688c1c0d24a2e97cd764f@gmail.com";
  x-conformance=sidf_compatible
Received-SPF: Pass (mail2-smtp-roc.national.inria.fr: domain of
  5764c029b688c1c0d24a2e97cd764f@gmail.com designates
  74.125.82.50 as permitted sender) identity=mailfrom;
  client-ip=74.125.82.50;
  receiver=mail2-smtp-roc.national.inria.fr;
  envelope-from="5764c029b688c1c0d24a2e97cd764f@gmail.com";
  x-sender="5764c029b688c1c0d24a2e97cd764f@gmail.com";
  x-conformance=sidf_compatible; x-record-type="v=spf1"
Received-SPF: None (mail2-smtp-roc.national.inria.fr: no sender
  authenticity information available from domain of
  postmaster@mail-wg0-f50.google.com) identity=helo;
  client-ip=74.125.82.50;
  receiver=mail2-smtp-roc.national.inria.fr;
  envelope-from="5764c029b688c1c0d24a2e97cd764f@gmail.com";
  x-sender="postmaster@mail-wg0-f50.google.com";
  x-conformance=sidf_compatible
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: AhkHAG7QJ1FKfVIyk2dsb2JhbABEgh0Eg2a7IYENFg4BAQEBCQkLCRQEI4IfAQEFJxEIARscAgMMBgULDQkWDwkDAgECARERAQUBHAYNCAKHewEDDwShKIwygnuEQQoZJw1ZiGUBBQyOTzqDQAOWOoEdhFeJDT+EKg
X-IPAS-Result: AhkHAG7QJ1FKfVIyk2dsb2JhbABEgh0Eg2a7IYENFg4BAQEBCQkLCRQEI4IfAQEFJxEIARscAgMMBgULDQkWDwkDAgECARERAQUBHAYNCAKHewEDDwShKIwygnuEQQoZJw1ZiGUBBQyOTzqDQAOWOoEdhFeJDT+EKg
X-IronPort-AV: E=Sophos;i="4.84,717,1355094000"; 
   d="scan'208";a="4135511"
Received: from mail-wg0-f50.google.com ([74.125.82.50])
  by mail2-smtp-roc.national.inria.fr with ESMTP/TLS/RC4-SHA; 22 Feb 2013 21:13:42 +0100
Received: by mail-wg0-f50.google.com with SMTP id es5so854751wgb.29
        for <caml-list@inria.fr>; Fri, 22 Feb 2013 12:13:42 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=gmail.com; s=20120113;
        h=x-received:message-id:date:from:user-agent:mime-version:to:subject
         :references:in-reply-to:content-type:content-transfer-encoding;
        bh=pgMP8rB8insECDIgxPoIcnLfzbLXOkG+NB99OC4pOmg=;
        b=umJAl7CUsLQ4POzfWA1pDWvo3SLs/H9LdySp+8hU1H/KiJa/JX2CFLp1LVTnBf2dHw
         HZVWd81F3xG4SnRHG7DP9dnx8xejVqDloU1eJo6VY6WS0MjxsaD6TWRZhwESVnV1sKVd
         QKqOE4bibZAqW56rADSGTV4WwKE6SEn9WL5VGRQB/eKzzZgQOkgepHRBmGDrOgPXa8ah
         TI6yHKCAG8X8x/uxyNA8ila3j0wQog5c9UVNtEnI2nLtj+Q3QB4IcP1lSvpp/OnOSnAx
         pJsillZPUJB3lRKrneoENRLYRcSv1+8uZuUnmFxLczAYBekHvCyQ90l+e4HLuoJNO5n0
         l+Mw==
X-Received: by 10.194.91.211 with SMTP id cg19mr5939870wjb.43.1361564022641;
        Fri, 22 Feb 2013 12:13:42 -0800 (PST)
Received: from [172.27.6.173] ([213.106.240.92])
        by mx.google.com with ESMTPS id j4sm354534wiz.10.2013.02.22.12.13.41
        (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128);
        Fri, 22 Feb 2013 12:13:41 -0800 (PST)
Message-ID: <5127D1AB.6090204@gmail.com>
Date: Fri, 22 Feb 2013 20:14:35 +0000
From: Matej Kosik <5764c029b688c1c0d24a2e97cd764f@gmail.com>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.12) Gecko/20130116 Icedove/10.0.12
MIME-Version: 1.0
To: OCaml <caml-list@inria.fr>
References: <5127AFD7.5040002@gmail.com> <Prayer.1.3.5.1302221833330.26859@hermes-1.csi.cam.ac.uk>
In-Reply-To: <Prayer.1.3.5.1302221833330.26859@hermes-1.csi.cam.ac.uk>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: [Caml-list] strange typechecking result

On 22/02/13 18:33, Leo White wrote:
>>
>
> I think that by default recursive uses of a function are monomorphic.
> You can fix this with an explicit polymorphic annotation:
>
> let rec f1: 'a. 'a -> unit = fun _ -> ()
> and f2 r1 = f1 r1.l1
> and f3 r2 = f1 r2.l2;;
>
> Regards,
>
> Leo
>

Yuri, Leo, thanks.

Now I see that there is even simpler program, that demonstrates the problem:

   let rec f1 _ =
     ()

   and f2 (value:int) =
     f1 value

   and f3 (value:char) =
     f1 value

The typechecker rejects it for similar reasons.

   File "test.ml", line 8, characters 5-10:
   Error: This expression has type char but an expression
          was expected of type int.

That's quite strange.

I would like to ask:

- Where is that restriction explained?
   (I've searched Ocaml reference manual for "monomorphic" but nothing
    relevant seemed to come up)

- Where are things like:

      'a. 'a -> unit

   described?

   I've already seen it in some document, but now I fail
   to find it again.