From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 23813 invoked from network); 3 Aug 2020 09:25:28 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 3 Aug 2020 09:25:28 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id B92109CA94; Mon, 3 Aug 2020 19:25:26 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id C5FB69CA83; Mon, 3 Aug 2020 19:24:47 +1000 (AEST) Received: by minnie.tuhs.org (Postfix, from userid 112) id 95AEE9CA7F; Mon, 3 Aug 2020 19:24:43 +1000 (AEST) Received: from freefriends.org (freefriends.org [96.88.95.60]) by minnie.tuhs.org (Postfix) with ESMTPS id D86C69CA7E for ; Mon, 3 Aug 2020 19:24:42 +1000 (AEST) X-Envelope-From: arnold@skeeve.com Received: from freefriends.org (freefriends.org [96.88.95.60]) by freefriends.org (8.14.7/8.14.7) with ESMTP id 0739OYCH005391 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 3 Aug 2020 03:24:35 -0600 Received: (from arnold@localhost) by freefriends.org (8.14.7/8.14.7/Submit) id 0739OYR7005390; Mon, 3 Aug 2020 03:24:34 -0600 From: arnold@skeeve.com Message-Id: <202008030924.0739OYR7005390@freefriends.org> X-Authentication-Warning: frenzy.freefriends.org: arnold set sender to arnold@skeeve.com using -f Date: Mon, 03 Aug 2020 03:24:34 -0600 To: tuhs@tuhs.org, doug@cs.dartmouth.edu, arnold@skeeve.com References: <202008021340.072Demtg086822@tahoe.cs.Dartmouth.EDU> <202008021357.072DvOYo024549@freefriends.org> <202008021713.072HD7Ba120877@tahoe.cs.Dartmouth.EDU> In-Reply-To: <202008021713.072HD7Ba120877@tahoe.cs.Dartmouth.EDU> User-Agent: Heirloom mailx 12.5 7/5/10 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Subject: Re: [TUHS] BTL summer employees X-BeenThere: tuhs@minnie.tuhs.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: The Unix Heritage Society mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" Doug McIlroy wrote: > >> Even high-school employees could make lasting contributions. I am > >> indebted to Steve for a technique he conceived during his first summer > >> assignment: using macro definitions as if they were units of associative > >> memory. This view of macros stimulated previously undreamed-of uses. > > > Can you give some examples of what this looked like? > > One useless, but telling, program of mine was a Turing-machine > simulator. Tape cells were represented by macros that contained > a symbol and the (macro) names of adjacent cells. New cells > could be generated as needed, with names derived from a counter. > A natural way to store the state-transition table (I forget > how it was actually done) would be as macros whose names > are the concatenation of state and symbol names. > > Path-compression as used in union-find algorithms originated > in a macroprocessor implementation by Bob Morris. Each graph > node was represented by a macro that pointed to or toward > the root of a tree spanning its graph component. Thanks Doug. I have to admit, I didn't really grok this. My mental processes seem to have frozen somewhat and I need to see something like this in code before I really understand it. :-) Thanks, Arnold