From owner-freebsd-chat Thu Dec 9 19:42:59 1999 Delivered-To: freebsd-chat@freebsd.org Received: from nisser.com (c1870039.telekabel.chello.nl [212.187.0.39]) by hub.freebsd.org (Postfix) with ESMTP id 56F181537A; Thu, 9 Dec 1999 19:42:56 -0800 (PST) (envelope-from roelof@nisser.com) Received: from nisser.com (roelof [10.0.0.2]) by nisser.com (8.9.3/8.9.2) with ESMTP id EAA12772; Fri, 10 Dec 1999 04:41:14 +0100 (CET) (envelope-from roelof@nisser.com) Message-ID: <38507672.25B7FB4F@nisser.com> Date: Fri, 10 Dec 1999 04:41:38 +0100 From: Roelof Osinga Organization: eboa - engineering buro Office Automation X-Mailer: Mozilla 4.7 [en] (WinNT; I) X-Accept-Language: en MIME-Version: 1.0 To: Brett Glass Cc: David Scheidt , Tani Hosokawa , Jonathon McKitrick , Alfred Perlstein , Kris Kennaway , freebsd-chat Subject: Re: Yahoo hacked last night References: <38502053.28737F7B@nisser.com> <4.2.0.58.19991209162117.00cc0670@localhost> <4.2.0.58.19991209200536.03b8b400@localhost> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-chat@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org Brett Glass wrote: > > If it's allowed to run to completion it will do a complete depth-first > search and generate all possible solutions -- provided, of course, that > the tree is finite. And not all trees are. And there are those that recurse before the path with the solution(s) is taken. Breadth first would solve that. > ... > Backward chaining is the mechanism of formal logic which Prolog > implements. It tries to "chain" backward from a statement to the > facts and rules which prove it to be true. Still doesn't ring a bell. The process is known as SLD-resolution being a refinement of SL-resolution. The logic texts still await reading but from what I picked up from regular texts I gather it is not unlike Robinsons' unification algorithm. The very algorithm used in type inference. In fact, from what I recall - we're talking very early 80's here, after all - some Prolog's are more or less based on that algorithm. There was an early text floating around from Leuven University or something describing how to roll your own Prolog. I was at the time doing an inference engine in Pascal/MT+ for 8 bit CP/M . > However, it still has some niceties that Icon doesn't. Regular > expressions as implemented in Perl are far less potent than > SNOBOL patterns. (The original SNOBOL book contains a > complete parser for the SNOBOL language in SNOBOL; the set > of patterns is only about 20 lines long. Sorry, but that's even longer ago . All I had at the time was some text print out from the CDC Cyber implementation. Later on I looked at it again, but in a cursory fashion. But one wonders whether SNOBOL's conciseness had something to do with it . From what I remember it gave APL a run for its money. Roelof -- Home is where the (@) http://eboa.com/ is. Telekabel home http://nisser.com/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message