From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Original-To: caml-list@yquem.inria.fr Delivered-To: caml-list@yquem.inria.fr Received: from nez-perce.inria.fr (nez-perce.inria.fr [192.93.2.78]) by yquem.inria.fr (Postfix) with ESMTP id 7E07DBB84 for ; Tue, 18 Apr 2006 10:57:27 +0200 (CEST) Received: from pauillac.inria.fr (pauillac.inria.fr [128.93.11.35]) by nez-perce.inria.fr (8.13.0/8.13.0) with ESMTP id k3I8vQDU018537 for ; Tue, 18 Apr 2006 10:57:27 +0200 Received: from concorde.inria.fr (concorde.inria.fr [192.93.2.39]) by pauillac.inria.fr (8.7.6/8.7.3) with ESMTP id KAA11132 for ; Tue, 18 Apr 2006 10:57:25 +0200 (MET DST) Received: from anthony.ics.uci.edu (anthony.ics.uci.edu [128.200.39.241]) by concorde.inria.fr (8.13.0/8.13.0) with SMTP id k3I8vOAk030032 for ; Tue, 18 Apr 2006 10:57:25 +0200 Received: (qmail 22098 invoked by uid 1000); 18 Apr 2006 08:58:25 -0000 Date: Tue, 18 Apr 2006 01:58:25 -0700 From: Christian Stork To: Jon Harrop , caml-list@inria.fr Subject: Re: [Caml-list] recursion/iterator question Message-ID: <20060418085825.GD21750@anthony.ics.uci.edu> Mail-Followup-To: Jon Harrop , caml-list@inria.fr References: <1145221898.16349.259200911@webmail.messagingengine.com> <200604170106.23660.jon@ffconsultancy.com> <20060417093635.GB13523@anthony.ics.uci.edu> <200604171807.47687.jon@ffconsultancy.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200604171807.47687.jon@ffconsultancy.com> X-Archive: encrypt User-Agent: Mutt/1.5.11 X-Miltered: at nez-perce with ID 4444A9F7.000 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)! X-Miltered: at concorde with ID 4444A9F4.000 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)! X-Spam: no; 0.00; recursion:01 iterator:01 rec:01 ocaml:01 compiler:01 2006:98 2006:98 806:98 021:98 wrote:01 wrote:01 caml-list:01 complains:01 matched:01 short:01 X-Spam-Checker-Version: SpamAssassin 3.0.3 (2005-04-27) on yquem.inria.fr X-Spam-Level: X-Spam-Status: No, score=0.0 required=5.0 tests=none autolearn=disabled version=3.0.3 On Mon, Apr 17, 2006 at 06:07:47PM +0100, Jon Harrop wrote: > On Monday 17 April 2006 10:36, Christian Stork wrote: > > Or, if you choose to represent triplets as lists of three elements, you can > > generalize Jon's solution to > > let rec combs = function > > | (0, _) -> [[]] > > | (n, es) when n > List.length es -> [] > > | (n, e::es) -> List.map (fun l -> e::l) (combs (n-1, es)) @ combs > > | (n, es) > > let triplets es = combs (3, es) > > Question to the rest of the list: The ocaml compiler complains with > > ... > > Warning P: this pattern-matching is not exhaustive. > > Here is an example of a value that is not matched: > > (1, []) > > (However, some guarded clause may match this value.) > > ... > > Am I right to assume there's no way to get rid of this warning short of > > disabling P-warnings on the command line? (I can't list all the lacking > > patterns since they depend on n, right?) > The lacking patterns are covered by (_, []), so you probably want: > | 0, _ | _, [] -> [[]] No, that would generate solutions shorter than the requested n elements. What we want is something like | 1, [] | 2, [] | 2, [_] | 3, [] | 3, [_] | 3, [_;_] ... | n, [] | n, [_] | n, [_;_] | ... | n, [_;...;_] (* n-1 times '_' *) -> [] Anyway, I think it's better not to use pattern matching but to use a simple if-then-else to circumvent the warning. -- Chris Stork <> Support eff.org! <> http://www.ics.uci.edu/~cstork/ OpenPGP fingerprint: B08B 602C C806 C492 D069 021E 41F3 8C8D 50F9 CA2F