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=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: fac41,9a0ff0bffdf63657 X-Google-Attributes: gidfac41,public X-Google-Thread: f43e6,9a0ff0bffdf63657 X-Google-Attributes: gidf43e6,public X-Google-Thread: 1108a1,9a0ff0bffdf63657 X-Google-Attributes: gid1108a1,public X-Google-Thread: 103376,4b06f8f15f01a568 X-Google-Attributes: gid103376,public From: "Robert Martin" Subject: Re: Software landmines (loops) Date: 1998/09/02 Message-ID: <6skfs7$2s6$1@hirame.wwa.com>#1/1 X-Deja-AN: 387364709 References: <6rf59b$2ud$1@nnrp1.dejanews.com> <6rfra4$rul$1@nnrp1.dejanews.com> <35DBDD24.D003404D@calfp.co.uk> <6sbuod$fra$1@hirame.wwa.com> <904556531.666222@miso.it.uq.edu.au> <6sgror$je8$3@news.indigo.ie> <6sh3qn$9p2$1@hirame.wwa.com> <6simjo$jnh$1@hirame.wwa.com> <35eeea9b.2174586@news.erols.com> <6sjj7n$3rr$1@hirame.wwa.com> <35f055a5.1431187@news.erols.com> <6sjnlu$83l$1@hirame.wwa.com> X-MimeOLE: Produced By Microsoft MimeOLE V4.72.2106.4 Organization: WorldWide Access - Midwestern Internet Services - www.wwa.com Newsgroups: comp.lang.eiffel,comp.object,comp.software-eng,comp.lang.ada Date: 1998-09-02T00:00:00+00:00 List-Id: Ell wrote in message ... >If you had quotes showing that "single entry single exit" was supposed to >be a key maxim of the structured paradigm you would quote it. At lesast >you should. Elliott, if Dijkstra had provided a nice one liner, I'd be glad to give it to you. And, after all, maybe he did and I just haven't found it. So what? The chapter is only a few pages long, the book is certain to be available at a nearby library or bookstore, so look it up. >Because all you've shown is Flowcahrt 101, that of course a flowchart >should have only one entry and one exit point on the *page*! I have no idea how you could have drawn that interpretation. First, I've never heard of such a convention. Second, it has nothing to do with the discussion in the cited chapter. The chapter is about structuring the flow of control. Dijkstra is making the point that unrestricted flow of control (i.e. goto) is harmful. He then shows four flowcharts that demonstrate the cannonical forms of flow control in structured programming. They are, sequence, decision, top exit iteration, and bottom exit iteration. He then goes on to recommend that all software be constructed of assemblages of these four control forms; and nothing but these four control forms. He then describes the four forms as having a single entry and a single exit. I strongly recommend that before you respond further to this thread, you read Dijkstra's material. >I've taken 4 formally named "Structured COBOL" courses so I've already >done my homework. Twenty-three years ago I was *teaching* "Structured COBOL" courses. Fortunately, we are not discussing the contents of structured COBOL courses. We are discussing the contents of Dijkstra's book "Structured Programming". If your courses failed to teach you about single-entry/single-exit, then I suggest you ask for your money back, because you got reamed. Robert C. Martin | Design Consulting | Training courses offered: Object Mentor | rmartin@oma.com | Object Oriented Design 14619 N Somerset Cr | Tel: (800) 338-6716 | C++ Green Oaks IL 60048 | Fax: (847) 918-1023 | http://www.oma.com "One of the great commandments of science is: 'Mistrust arguments from authority.'" -- Carl Sagan