Date: Fri, 10 Dec 1999 04:41:38 +0100 From: Roelof Osinga <roelof@nisser.com> To: Brett Glass <brett@lariat.org> Cc: David Scheidt <dscheidt@enteract.com>, Tani Hosokawa <unknown@riverstyx.net>, Jonathon McKitrick <jcm@dogma.freebsd-uk.eu.org>, Alfred Perlstein <bright@wintelcom.net>, Kris Kennaway <kris@hub.freebsd.org>, freebsd-chat <chat@FreeBSD.ORG> Subject: Re: Yahoo hacked last night Message-ID: <38507672.25B7FB4F@nisser.com> References: <38502053.28737F7B@nisser.com> <4.2.0.58.19991209162117.00cc0670@localhost> <4.2.0.58.19991209200536.03b8b400@localhost>
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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 <g>. > 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 <g>. 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 <g>. 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
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