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 QAA18947; Fri, 8 Oct 2004 16:32:54 +0200 (MET DST) 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 QAA18936 for ; Fri, 8 Oct 2004 16:32:52 +0200 (MET DST) Received: from smtp1.adl2.internode.on.net (smtp1.adl2.internode.on.net [203.16.214.181]) by nez-perce.inria.fr (8.13.0/8.13.0) with ESMTP id i98EWoWJ026189 for ; Fri, 8 Oct 2004 16:32:51 +0200 Received: from [192.168.1.200] (ppp213-29.lns2.syd3.internode.on.net [203.122.213.29]) by smtp1.adl2.internode.on.net (8.12.9/8.12.9) with ESMTP id i98EWe4Y019709; Sat, 9 Oct 2004 00:02:41 +0930 (CST) Subject: Re: [Caml-list] Recursive lists From: skaller Reply-To: skaller@users.sourceforge.net To: Keith Wansbrough Cc: Luca Pascali , caml-list In-Reply-To: References: Content-Type: text/plain Message-Id: <1097245959.19722.27.camel@pelican.wigram> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.2.2 (1.2.2-4) Date: 09 Oct 2004 00:32:39 +1000 Content-Transfer-Encoding: 7bit X-Miltered: at nez-perce with ID 4166A512.001 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)! X-Loop: caml-list@inria.fr X-Spam: no; 0.00; caml-list:01 sourceforge:01 2004:99 descent:01 acyclic:01 9660:01 glebe:01 tokens:01 equality:01 token:01 nsw:01 snail:02 lazy:02 nodes:02 node:02 Sender: owner-caml-list@pauillac.inria.fr Precedence: bulk On Fri, 2004-10-08 at 23:31, Keith Wansbrough wrote: > > Can some functions of the List library support the use of the recursive > > lists? > How could they do this? > You might be able to do it by keeping a list of all the nodes you've > visited, and using physical equality to check if you have already > visited a node. I use that technique to perform recursive descent on acyclic graphs, which the recursive list is. For a list with the cycle *known* to be length 1, this is very cheap, since you only need to compare against previous element. You can also use lazy evaluation. An example of a stream (infinite list) being a *correct* data structure is a list of tokens with a cycle on the 'end of file' token. Much easier to analyse with matches against substring patterns .. since you don't have to worry about the end of the list. -- John Skaller, mailto:skaller@users.sf.net voice: 061-2-9660-0850, snail: PO BOX 401 Glebe NSW 2037 Australia Checkout the Felix programming language http://felix.sf.net ------------------- 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