From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mail4-relais-sop.national.inria.fr (mail4-relais-sop.national.inria.fr [192.134.164.105])
	by walapai.inria.fr (8.13.6/8.13.6) with ESMTP id p65NP3ev030745
	for <caml-list@sympa-roc.inria.fr>; Wed, 6 Jul 2011 01:25:03 +0200
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: AmYDAAKcE05KfVO2kGdsb2JhbAA9AQMSnF+LJwgUAQEBAQkJDQcUBCGIeqcljnKES4khAgMGhjAEhz2KeYYVhg48gT2CKQ
X-IronPort-AV: E=Sophos;i="4.65,481,1304287200"; 
   d="scan'208";a="102587242"
Received: from mail-pv0-f182.google.com ([74.125.83.182])
  by mail4-smtp-sop.national.inria.fr with ESMTP/TLS/RC4-SHA; 06 Jul 2011 01:24:57 +0200
Received: by pvg11 with SMTP id 11so9484395pvg.27
        for <caml-list@inria.fr>; Tue, 05 Jul 2011 16:24:55 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=gmail.com; s=gamma;
        h=sender:subject:mime-version:content-type:from:in-reply-to:date:cc
         :content-transfer-encoding:message-id:references:to:x-mailer;
        bh=skSKYMOrBkJbfF7hkf+sA5H6mkcXcxBd5yhG39H/uv8=;
        b=gUmAv8K8lAokiN2fJ3AVW4JHpjRB7nQj/DglFR4nRxca3ES5CgZn4o5/GB5g53pgvL
         Qfod8PuyQEYl+xiVw9cjGHAtnJoOJPMjKXokZ/HZ5Fx1DBkOwEZ/hPARreKCNu9KvUpp
         3kLwxxVjBx10X74I4IL481Z28jGj7Pns1R0Vw=
Received: by 10.68.34.228 with SMTP id c4mr9513589pbj.463.1309908295520;
        Tue, 05 Jul 2011 16:24:55 -0700 (PDT)
Received: from tet.garrigue.jp (58x158x128x157.ap58.ftth.ucom.ne.jp [58.158.128.157])
        by mx.google.com with ESMTPS id d3sm1310903pbh.69.2011.07.05.16.24.53
        (version=TLSv1/SSLv3 cipher=OTHER);
        Tue, 05 Jul 2011 16:24:54 -0700 (PDT)
Sender: Jacques Garrigue <jacques.garrigue@gmail.com>
Mime-Version: 1.0 (Apple Message framework v1084)
Content-Type: text/plain; charset=us-ascii
From: Jacques Garrigue <garrigue@math.nagoya-u.ac.jp>
In-Reply-To: <alpine.LNX.2.00.1107051757280.9196@linmac>
Date: Wed, 6 Jul 2011 08:24:51 +0900
Cc: caml-list@inria.fr
Message-Id: <098226D8-77AA-4F80-97A5-F72F47C6A98E@math.nagoya-u.ac.jp>
References: <alpine.LNX.2.00.1107051757280.9196@linmac>
To: malc <av1474@comtv.ru>
X-Mailer: Apple Mail (2.1084)
Content-Transfer-Encoding: 8bit
X-MIME-Autoconverted: from quoted-printable to 8bit by walapai.inria.fr id p65NP3ev030745
Subject: Re: [Caml-list] Type inference and marshalling

On 2011/07/05, at 22:59, malc wrote:

> Perhaps someone could explain why following behaves the way it does:
> 
> ~$ ocaml
>        Objective Caml version 3.11.2
> 
> # let f ic = let i = input_value ic in let j = i + 1 in LargeFile.seek_in ic i;;
> Warning Y: unused variable j.
> val f : in_channel -> unit = <fun>

The return type of input_value being 'a, which gets generalized by the
relaxed value restriction, i gets the polymorphic type "forall 'a. 'a".
So you can use it both as an int and an int64.
==> input_value is an unsafe function, you should always write a type
	annotation on its return type.

> # let f ic = let i = input_value ic in let j = i + 1 in LargeFile.seek_in ic j;;
> Error: This expression has type int but an expression was expected of type
>         int64

j being the result of an integer addition, it has type int, and cannot be used
as int64.

Jacques