From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (from majordomo@localhost) by pauillac.inria.fr (8.7.6/8.7.3) id EAA15293; Fri, 7 Nov 2003 04:53:40 +0100 (MET) X-Authentication-Warning: pauillac.inria.fr: majordomo set sender to owner-caml-list@pauillac.inria.fr using -f Received: from nez-perce.inria.fr (nez-perce.inria.fr [192.93.2.78]) by pauillac.inria.fr (8.7.6/8.7.3) with ESMTP id EAA15334 for ; Fri, 7 Nov 2003 04:53:39 +0100 (MET) Received: from kurims.kurims.kyoto-u.ac.jp (kurims.kurims.kyoto-u.ac.jp [130.54.16.1]) by nez-perce.inria.fr (8.11.1/8.11.1) with ESMTP id hA73rb105795 for ; Fri, 7 Nov 2003 04:53:37 +0100 (MET) Received: from localhost (suiren.kurims.kyoto-u.ac.jp [130.54.16.25]) by kurims.kurims.kyoto-u.ac.jp (8.9.3p2-20030924/3.7W) with ESMTP id MAA22650; Fri, 7 Nov 2003 12:53:04 +0900 (JST) To: erayo@cs.bilkent.edu.tr, exa@kablonet.com.tr Cc: caml-list@inria.fr Subject: Re: [Caml-list] A grave bug in logical shift right op? In-Reply-To: <200311070535.00172.exa@kablonet.com.tr> References: <200311070535.00172.exa@kablonet.com.tr> X-Mailer: Mew version 1.94.2 on Emacs 21.2 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: <20031107125304T.garrigue@kurims.kyoto-u.ac.jp> Date: Fri, 07 Nov 2003 12:53:04 +0900 From: Jacques Garrigue X-Dispatcher: imput version 20000228(IM140) X-Loop: caml-list@inria.fr X-Spam: no; 0.00; caml-list:01 grave:01 bug:01 jacques:01 eray:01 ozkural:01 ledit:01 3.07:01 printf:01 printf:01 cipher:01 litteral:01 fffffff:01 floats:01 jacques:01 Sender: owner-caml-list@pauillac.inria.fr Precedence: bulk From: Eray Ozkural > I'm using the debian package in testing.... > > orion:fealn-attack$ ledit ocaml > Objective Caml version 3.07+2 > > # Printf.printf "%X" 0xffffffff;; > 7FFFFFFF- : unit = () > # Printf.printf "%lx" (Int32.of_int 0xffffffff);; > ffffffff- : unit = () > # -1 lsr 24;; > - : int = 127 > # Int32.shift_right_logical (Int32.of_int (-1)) 24;; > - : int32 = 255l > > What's going on here? Something's eating the most significant bit in > both hexadecimal output routine and the logical shift right > operator. Somebody please help me! My cipher isn't working!!! Sure, the int type has only 31 bits. In good math, (2 ^ 31 - 1) quo 2 ^ 24 is 127, as far as I know. Note that the problem with your first example has already been discussed. A litteral bigger than the biggest possible integer should probably trigger an error/exception. A bit more curions is your second example: since 0xffffffff = 0x7fffffff = -1, converting it to int32 gives -1l (the 32-bit value for -1), which happens to be 0xffffffffl. If you want to do 32-bit computations, you must use only 32-bit integers. This shouldn't be too inefficient as long as you use loops rather than function calls (the same recommandations as for floats apply, I believe). Jacques Garrigue ------------------- To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ Beginner's list: http://groups.yahoo.com/group/ocaml_beginners