From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,bc1361a952ec75ca X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2001-07-31 14:29:20 PST Path: archiver1.google.com!newsfeed.google.com!newsfeed.stanford.edu!paloalto-snf1.gtei.net!news.gtei.net!enews.sgi.com!newshub2.rdc1.sfba.home.com!news.home.com!news1.rdc2.on.home.com.POSTED!not-for-mail Message-ID: <3B672322.B5EA1B66@home.com> From: "Warren W. Gay VE3WWG" X-Mailer: Mozilla 4.75 [en] (Windows NT 5.0; U) X-Accept-Language: en MIME-Version: 1.0 Newsgroups: comp.lang.ada Subject: Re: The concept of := (was How to make Ada a dominant language) References: <3B6555ED.9B0B0420@sneakemail.com> <87n15lxzzv.fsf@deneb.enyo.de> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Date: Tue, 31 Jul 2001 21:29:19 GMT NNTP-Posting-Host: 24.141.193.224 X-Complaints-To: abuse@home.net X-Trace: news1.rdc2.on.home.com 996614959 24.141.193.224 (Tue, 31 Jul 2001 14:29:19 PDT) NNTP-Posting-Date: Tue, 31 Jul 2001 14:29:19 PDT Organization: Excite@Home - The Leader in Broadband http://home.com/faster Xref: archiver1.google.com comp.lang.ada:10897 Date: 2001-07-31T21:29:19+00:00 List-Id: Keith Thompson wrote: > Florian Weimer writes: > > Russ Paielli <18k11tm001@sneakemail.com> writes: > [...] > > > What's so great about ":="? Why not use "$=" or "%="? > > > > ':=' was already used to denote assignent even before programming > > languages existed. > > Is that true? I would have assumed that the concept of assignment > didn't exist, or at least wasn't very widespread, before programming > languages existed. Equality assertions using "=" are far more common > in mathematics. In response to "the concept of assignment didn't exist" : Quoting from "Imperative Programming Languages: Vol II" by Peter H. Salus, Series Editor in Chief (ISBN 1-57870-009-4) : "In 1954, a project was begun under the leadership of John Backus at IBM to develop an 'automatice programming' systemthat would convert programs written in a *mathematical notation* to machine instructions for the IBM 704 computer. Many were skeptical about the success of the project because, at the time, computer memories were so small and expensive and execution time so valuable that it was believed necesssary for the compiled program to be almost as efficient as that produced by a good assembly language programmer. ..." The chapter goes on to describe the beginnings of FORTRAN. The point of this excerpt was that there was a "mathematical notation" in use. While this is not described, I would not be surprised that any step-wise description would have some sort of "assignment notation" like :=, since mathematics types would be loath to say =. Further note that John Backus was involved here, and he is the one behind "BNF". See http://www-groups.dcs.st-andrews.ac.uk/~history/Mathematicians/Backus.html for picture and other background. >From http://www.digitalcentury.com/encyclo/update/backus.html : "After FORTRAN, Backus turned his focus to other elements of computer programming. In 1959, he developed a notation called the Backus-Naur Form. It describes grammatical rules for high-level languages, and has been adapted for use in a number of languages." What is interesting about BNF, it uses the ::= notation for describing grammars, for example : ::= It's not hard to imagine that while grammar rules may use ::=, then the assignment rule may indeed have been := . -- Warren W. Gay VE3WWG http://members.home.net/ve3wwg