From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on yquem.inria.fr X-Spam-Level: * X-Spam-Status: No, score=1.1 required=5.0 tests=AWL,SPF_NEUTRAL autolearn=disabled version=3.1.3 Received: from mail4-relais-sop.national.inria.fr (mail4-relais-sop.national.inria.fr [192.134.164.105]) by yquem.inria.fr (Postfix) with ESMTP id 874A3BC6B for ; Wed, 7 Nov 2007 11:22:03 +0100 (CET) X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AgAAAB4gMUfAXQInh2dsb2JhbACOewEBAQgKKQ X-IronPort-AV: E=Sophos;i="4.21,383,1188770400"; d="scan'208";a="19024957" Received: from concorde.inria.fr ([192.93.2.39]) by mail4-smtp-sop.national.inria.fr with ESMTP; 07 Nov 2007 11:22:03 +0100 Received: from mail4-relais-sop.national.inria.fr (mail4-relais-sop.national.inria.fr [192.134.164.105]) by concorde.inria.fr (8.13.6/8.13.6) with ESMTP id lA7AM2KA019858 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=OK) for ; Wed, 7 Nov 2007 11:22:02 +0100 X-IronPort-AV: E=Sophos;i="4.21,383,1188770400"; d="scan'208";a="19024956" Received: from peray.inria.fr (HELO ausone.inria.fr) ([128.93.8.98]) by mail4-relais-sop.national.inria.fr with SMTP; 07 Nov 2007 11:22:02 +0100 Received: by ausone.inria.fr (sSMTP sendmail emulation); Wed, _d Nov 2007 11:21:23 +0100 From: "Nicolas Pouillard" Cc: tmp123 , caml-list Subject: Re: [Caml-list] log function without evaluate arguments To: "till.varoquaux" References: <47309EEC.4080706@menta.net> <1194373338-sup-9994@ausone.local> <9d3ec8300711061040l424aac69y4b859a029d815089@mail.gmail.com> In-Reply-To: <9d3ec8300711061040l424aac69y4b859a029d815089@mail.gmail.com> Date: Wed, 07 Nov 2007 11:21:23 +0100 Message-Id: <1194430860-sup-6629@port-ext2.ensta.fr> User-Agent: Sup/0.2 Content-Type: text/plain; charset=UTF-8 X-Miltered: at concorde with ID 473191CA.000 by Joe's j-chkmail (http://j-chkmail . ensmp . fr)! X-Spam: no; 0.00; kprintf:01 printf:01 printf:01 val:01 fprintf:01 fprintf:01 fmt:01 fmt:01 wrote:01 caml-list:01 computation:01 computation:01 boolean:01 lazy:02 parameters:03 Excerpts from till.varoquaux's message of Tue Nov 06 19:40:19 +0100 2007: > On 11/6/07, Nicolas Pouillard wrote: > > Excerpts from tmp123's message of Tue Nov 06 18:05:48 +0100 2007: > > > Hello, > > > > > > In order to implement a function that prints log messages only, by > > > example, if a boolean flag is true, and does nothing elsewhere, I've > > > been reading the (long) post sequence "kprintf with user formatters" > > > (2004 Jun 30). > > > > > > In this context, "does nothing" means not convert parameters to text nor > > > evaluate them. > > > > Have a look to the Printf.ifprintf [1] function, it does exactly what you want. > > > > Regards, > > > Actually it doesn't: > > log (lazy (Printf.printf "%s" (awfully_long_computation ()))) > > when log_val is false (or sylvain's solution, which I prefer), will > not behave like > > Printf.ifprinf "%s" (awfully_long_computation ()) > > (it won't evaluate its arguments). Of course but you should use %a: let log fmt = if debug_mode then Printf.fprintf fmt else Printf.ifprintf fmt;; let awfully_long_computation' oc () = Printf.fprintf "%s" (awfully_long_computation ());; log "%a" awfully_long_computation' () Regards, -- Nicolas Pouillard aka Ertai