From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <edwin+ml-ocaml@etorok.net>
X-Original-To: caml-list@sympa.inria.fr
Delivered-To: caml-list@sympa.inria.fr
Received: from mail1-relais-roc.national.inria.fr (mail1-relais-roc.national.inria.fr [192.134.164.82])
	by sympa.inria.fr (Postfix) with ESMTPS id 0BEAE7EDC2
	for <caml-list@sympa.inria.fr>; Thu, 22 Nov 2012 11:33:40 +0100 (CET)
Received-SPF: None (mail1-smtp-roc.national.inria.fr: no sender
  authenticity information available from domain of
  edwin+ml-ocaml@etorok.net) identity=pra;
  client-ip=176.9.138.55;
  receiver=mail1-smtp-roc.national.inria.fr;
  envelope-from="edwin+ml-ocaml@etorok.net";
  x-sender="edwin+ml-ocaml@etorok.net";
  x-conformance=sidf_compatible
Received-SPF: Pass (mail1-smtp-roc.national.inria.fr: domain of
  edwin+ml-ocaml@etorok.net designates 176.9.138.55 as
  permitted sender) identity=mailfrom; client-ip=176.9.138.55;
  receiver=mail1-smtp-roc.national.inria.fr;
  envelope-from="edwin+ml-ocaml@etorok.net";
  x-sender="edwin+ml-ocaml@etorok.net";
  x-conformance=sidf_compatible; x-record-type="v=spf1"
Received-SPF: Pass (mail1-smtp-roc.national.inria.fr: domain of
  postmaster@mail.etorok.net designates 176.9.138.55 as
  permitted sender) identity=helo; client-ip=176.9.138.55;
  receiver=mail1-smtp-roc.national.inria.fr;
  envelope-from="edwin+ml-ocaml@etorok.net";
  x-sender="postmaster@mail.etorok.net";
  x-conformance=sidf_compatible; x-record-type="v=spf1"
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: AgIFAOH+rVCwCYo3/2dsb2JhbABEgmyDNbt+FnOCHgEBBSMdAQE2Ag8LGAICBRYLAgIJAwIBAgFFEwYCAogKAwesB3CDRwEFjycGgSKLEoEqghSBE5YCgRyPJYJx
X-IronPort-AV: E=Sophos;i="4.83,299,1352070000"; 
   d="scan'208";a="182683986"
Received: from mail.etorok.net ([176.9.138.55])
  by mail1-smtp-roc.national.inria.fr with ESMTP; 22 Nov 2012 11:33:39 +0100
Received: from [IPv6:2a02:2f02:1022:9089:1e6f:65ff:fe23:db0d] (unknown [IPv6:2a02:2f02:1022:9089:1e6f:65ff:fe23:db0d])
	by mail.etorok.net (Postfix) with ESMTPSA id B967746AE
	for <caml-list@inria.fr>; Thu, 22 Nov 2012 11:33:38 +0100 (CET)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=etorok.net;
	s=MAILOUT; t=1353580418;
	bh=mmZdaLkY57SY2qDkQV/iAdxBpbkYuRZmC6ol9E5lbVA=;
	h=Message-ID:Date:From:MIME-Version:To:Subject:References:
	 In-Reply-To:Content-Type:Content-Transfer-Encoding;
	b=RLiEEeas50QyT6TkilzfDn+ytZvSYRBcva7HDaCbQWXwOmQHkdSVkFW/S5pn0zIuz
	 0c/BqieobEDIzKtLwPqDrGogv0xW2tfpi+BeuaNDEDSgsFdng26Keb+ehe63mMIMlZ
	 I2rDLB9LiTrnFeXgQGM1YevBrqdu175JFLe1cbfw=
Message-ID: <50ADFF81.4000300@etorok.net>
Date: Thu, 22 Nov 2012 12:33:37 +0200
From: =?UTF-8?B?VMO2csO2ayBFZHdpbg==?= <edwin+ml-ocaml@etorok.net>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.10) Gecko/20121027 Icedove/10.0.10
MIME-Version: 1.0
To: caml-list@inria.fr
References: <b3cd867690b0f42d9c5a3bb1b22f7b2d@lipn.univ-paris13.fr>
In-Reply-To: <b3cd867690b0f42d9c5a3bb1b22f7b2d@lipn.univ-paris13.fr>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
X-Virus-Scanned: clamav-milter 0.97.6 at mail
X-Virus-Status: Clean
Subject: Re: [Caml-list] Lazyness and exceptions

On 11/22/2012 12:29 PM, Jean-vincent.Loddo@lipn.univ-paris13.fr wrote:
> Hello,
> 
> I have observed a strange behaviour of lazy values when an exception is raised. Here a minimal code that reproduces the behaviour:
> 
> # let action =
>     let thunk () =
>       Printf.printf "aaa\n";
>       failwith "bbb"
>     in
>     lazy (thunk ());;
> 
> val action : unit lazy_t = <lazy>
> 
> # Lazy.force action ;;
> aaa
> Exception: Failure "bbb".
> 
> # Lazy.force action ;;
> Exception: Failure "bbb".
> 
> The lazy value seems to be (correctly) not re-evaluated but the exception is (strangely) raised again. Why does this happen?

Its the documented behavior:
http://caml.inria.fr/pub/docs/manual-ocaml/libref/Lazy.html

Unfortunately the original backtrace will be lost.

--Edwin