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[extremeprogramming] Re: only code what you need today - rubbish !

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  • Robert C. Martin
    ... Not for today. The problems *may* come tomorrow. If on the other hand you try to anticipate tomorrows problems and protect yourself from them, you: 1)
    Message 1 of 20 , Feb 1, 2000
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      > -----Original Message-----
      > From: cbrooksbank@...
      > [mailto:cbrooksbank@...]
      > Sent: Tuesday, February 01, 2000 10:52 AM
      > To: extremeprogramming@egroups.com
      > Subject: [extremeprogramming] only code what you need today -
      > rubbish !
      >
      >
      > If you always write the simplist ( and the most specific )
      > solution to your
      > current immediate requirement you will generate problems.

      Not for today. The problems *may* come tomorrow. If on the other hand
      you try to anticipate tomorrows problems and protect yourself from them,
      you:

      1) make the software bigger and more complex than it needs to be right
      now.

      2) will guess wrong part of the time and force the next guy to undo, or
      work around, what you did.

      3) will spend a lot of time worrying about things that may never happen.

      BTW, XP doesn't recommend that you DO the simplest thing that could
      work. XP recommends that you consider WHAT the simplest thing that
      could possible work might be, and then extrapolate from there. Assume
      simplicity first.

      > The next guy that comes along with a slightly different
      > problem will write his
      > own specific class. It would take longer to work back looking
      > for a way
      > to generlalise the solution at a higher class level.

      It might indeed take longer. But the rules of XP force you to do it
      anyway. XP does not allow duplicate code in any form. Thus, when you
      find duplication, you must abstract it out.

      > With
      > lots of programmers
      > you get lots of classes over time, likely some bits will be
      > cut and paste
      > from other classes.

      Cut and paste is not allowed in XP because it is a form of duplication.
      The duplication must be factored out. We find that this makes us go
      faster in the long run.

      > When a bug is fixed or implementation
      > improved its only
      > fixed in some of these bits of code.

      Shouldn't happen in XP.

      > A new maintenance
      > programmer has lots of
      > bits
      > of code to work with instead of just one. Some will be subtly
      > different with
      > their own bugs. Your best coders will hate you for making
      > them produce inelegant
      > designs
      > and leave for other companys. Tell me Im wrong ( Im sure you
      > will ) . . .

      You aren't wrong. You just misunderstand XP. XP recommend that you do
      *exactly* what you recommend; with one exception. In XP we build the
      abstractions as soon as there is any duplication. Not when we suspect
      that there *might* be duplication. The rule in XP is "The second use
      pays for generality."


      Robert C. Martin | "Uncle Bob" | Training Courses:
      Object Mentor Inc. | rmartin@... | OOD, Patterns, C++,
      Java,
      PO Box 85 | Tel: (800) 338-6716 | Extreme Programming.
      Grayslake IL 60030 | Fax: (847) 548-6853 |
      http://www.objectmentor.com

      "One of the great commandments of science is:
      'Mistrust arguments from authority.'" -- Carl Sagan
    • Michael C. Feathers
      Nick, This is where things get dangerous in mailing lists. Below the last edit, I said that you end up in trouble if you don t surround doing the simplest
      Message 2 of 20 , Feb 1, 2000
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        Nick,

        This is where things get dangerous in mailing
        lists. Below the last edit, I said that you end up in
        trouble if you don't surround 'doing the simplest
        thing with other practices.' The net result of a lot
        of little locally advantageous changes is a big
        ball of mud, if you don't refactoring and simplify
        along the way.

        "Simple" works at two levels: simple changes to
        add the functionality that you need and
        "simple" overall design. You maintain the
        latter by refactoring.

        So, being clearer. The answer is, yes, do the
        simplest thing. But do the other practices as
        well, especially the testing and refactoring,
        so that you do not end up with the cruft that
        the original poster mentioned.

        Regarding the other question, you code
        what you need for each test that you have
        to run to get the functionality that your
        customer needs for this iteration.

        Michael

        ----- Original Message -----
        From: Pratt, Nick <npratt@...>
        > -----Original Message-----
        > From: Michael C. Feathers [mailto:mfeathers@...]
        > Sent: Tuesday, February 01, 2000 12:14
        > To: extremeprogramming@egroups.com
        > Subject: [extremeprogramming] Re: only code what you need today -
        > rubbish !
        >
        > [snip snip]
        >
        > Sure, if you only write the simplest solution to your
        > immediate requirement -- and that is all that you do,
        > you will end up in trouble.
        >
        > Don't do that.
        >
        > Question:
        > =========
        >
        > Isnt that what XP states, or did I misread/misunderstand what Kent
        wrote in
        > his book? Isnt one of the XP principles - code for today, ie the
        simplest
        > solution to your immediate requirement?
        >
        > I fully appreciate that if you are going to add some new functionality
        in
        > say, 2 weeks, then maybe you should code for that new addition, but at
        what
        > point do you call the cut-off. How long is ok to code for - 1 week, 1
        month,
        > an iteration?

        ---------------------------------------------------
        Michael Feathers mfeathers@...
        Object Mentor Inc. www.objectmentor.com
        Training/Mentoring/Development
        -----------------------------------------------------
        "You think you know when you can learn, are more sure when
        you can write, even more when you can teach, but certain when
        you can program. " - Alan Perlis
      • Thomas Matelich
        zhon johansen wrote: original article:http://www.egroups.com/group/extremeprogramming/?start =1178 ... and probably should ... probably don t
        Message 3 of 20 , Feb 1, 2000
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          zhon johansen <zho-@...> wrote:
          original article:http://www.egroups.com/group/extremeprogramming/?start
          =1178
          > This message is an example of how one XP practice in isolation can
          and probably should
          > be attacked. XP is a tightly knit collection of Values and Practices.
          >
          > Your question assumes you don't do
          > *refactoring* to keep the design elegant, which means you
          probably don't have
          > *unit tests* to catch mistakes. You are probably not
          > *pair programming* to give you confidence. You are also probably
          missing an
          > *onsite customer* telling you the business requirements and that
          missing customer
          > is probably not writing
          > *functional tests* so you can know when you are finished...
          >
          > HTH,
          >
          > Zhon
          >

          One more important factor in this problem is communication. If there
          was good communication, developer B would talk to developer A and find
          out that there is something that could be refactored into what he needs.
        • Ron Jeffries
          ... As I read the text and walk the walk, it means exactly that: DO the simplest thing that could possibly work. See, for example: p 38: Treat every problem as
          Message 4 of 20 , Feb 1, 2000
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            At 12:17 PM 2/1/2000 -0600, you wrote:
            >BTW, XP doesn't recommend that you DO the simplest thing that could
            >work. XP recommends that you consider WHAT the simplest thing that
            >could possible work might be, and then extrapolate from there. Assume
            >simplicity first.

            As I read the text and walk the walk, it means exactly that: DO the
            simplest thing that could possibly work. See, for example:

            p 38: Treat every problem as if it can be solved with ridiculous simplicity.

            p 103: The design strategy in XP is to always have the simplest design that
            runs the current test suite.

            p 104: We should assume that the simplest design we can imagine possibly
            working will work. This will give us time to do a thorough job in case the
            simples design doesn't work.

            Of course, one often falls short of the goal of always doing the simplest
            thing that could possibly work. Sometimes fear is just too much. Sometimes
            we don't think of the simplest thing until later. Then the rules of code
            simplicity encourage us to reduce the system back to where it belongs.

            Regards,

            Ron Jeffries
            Extreme Programming Training and Consultation
            www.XProgramming.com
          • Joshua Kerievsky
            Robert Martin writes ... Wiki has had a page called DoTheSimplestThingThatCouldPossiblyWork for well over a year now, and the expression has certainly made its
            Message 5 of 20 , Feb 1, 2000
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              Robert Martin writes
              >>BTW, XP doesn't recommend that you DO the simplest thing that could
              >>work. XP recommends that you consider WHAT the simplest thing that
              >>could possible work might be, and then extrapolate from there. Assume
              >>simplicity first.

              Ron Jeffries responds:
              >As I read the text and walk the walk, it means exactly that: DO the
              >simplest thing that could possibly work.

              Wiki has had a page called DoTheSimplestThingThatCouldPossiblyWork for well
              over a year now, and the expression has certainly made its way into the
              culture. However, Kent recently wrote in an email thread I exchanged with him:
              ----
              Note that I never said "do the simplest thing that could possibly work".
              That would be stupid. I try to get people to think in terms of simplicity,
              hence the phrasing "what is the simplest..." It's a mantra.
              ----

              I personally like the question better than the statement. The question is
              an invitation to think - it might lead to a 10 minute round-table on just
              what is the simplest thing. The statement form (Do The...) may not invite
              enough reflection.

              -jk





              regards
              jk


              _______________________________
              Industrial Logic, Inc.
              Joshua Kerievsky, founder
              mailto:joshua@...
              http://industriallogic.com
              415-292-6266
              415-292-6267 (fax)
            • Ron Jeffries
              I could be mistaken, but I m sure Kent did tell the C3 team exactly that. Of course a lot of what we told them has been refined. Kent is usually more extreme
              Message 6 of 20 , Feb 1, 2000
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                I could be mistaken, but I'm sure Kent did tell the C3 team exactly that.
                Of course a lot of what we told them has been refined. Kent is usually more
                extreme than I am, but in my simple way I've just been doing what he told
                me and I've never gone wrong yet with the simplest thing "that could
                possibly work".

                I can't help thinking, so I don't worry about accidentally forgetting to do
                so. Perhaps I should. What were we talking about?

                Oh, yeah, simplicity. Certainly it is a mantra. But when you do it, it
                seems to work. Kent should try it ... ;->

                Ron

                At 12:08 PM 2/1/2000 -0800, you wrote:
                >Robert Martin writes
                > >>BTW, XP doesn't recommend that you DO the simplest thing that could
                > >>work. XP recommends that you consider WHAT the simplest thing that
                > >>could possible work might be, and then extrapolate from there. Assume
                > >>simplicity first.
                >
                >Ron Jeffries responds:
                > >As I read the text and walk the walk, it means exactly that: DO the
                > >simplest thing that could possibly work.
                >
                >Wiki has had a page called DoTheSimplestThingThatCouldPossiblyWork for well
                >over a year now, and the expression has certainly made its way into the
                >culture. However, Kent recently wrote in an email thread I exchanged with him:
                >----
                >Note that I never said "do the simplest thing that could possibly work".
                >That would be stupid. I try to get people to think in terms of simplicity,
                >hence the phrasing "what is the simplest..." It's a mantra.
                >----
                >
                >I personally like the question better than the statement. The question is
                >an invitation to think - it might lead to a 10 minute round-table on just
                >what is the simplest thing. The statement form (Do The...) may not invite
                >enough reflection.
                >
                >-jk
                >
                >
                >
                >
                >
                >regards
                >jk
                >
                >
                >_______________________________
                >Industrial Logic, Inc.
                >Joshua Kerievsky, founder
                >mailto:joshua@...
                >http://industriallogic.com
                >415-292-6266
                >415-292-6267 (fax)
                >
                >
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                Ron Jeffries
                Extreme Programming Training and Consultation
                www.XProgramming.com
              • Michael C. Feathers
                ... From: Joshua Kerievsky ... well ... the ... work . ... simplicity, ... I like how Chet Hedrickson of the C3 team put it on
                Message 7 of 20 , Feb 1, 2000
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                  ----- Original Message -----
                  From: Joshua Kerievsky <joshua@...>
                  > Wiki has had a page called DoTheSimplestThingThatCouldPossiblyWork for
                  well
                  > over a year now, and the expression has certainly made its way into
                  the
                  > culture. However, Kent recently wrote in an email thread I exchanged
                  with him:
                  > ----
                  > Note that I never said "do the simplest thing that could possibly
                  work".
                  > That would be stupid. I try to get people to think in terms of
                  simplicity,
                  > hence the phrasing "what is the simplest..." It's a mantra.
                  > ----

                  I like how Chet Hedrickson of the C3 team put it on Wiki:
                  "The rule is, 'Do the simplest thing that could possibly
                  work', not the most stupid."

                  Whenever I can draw the distinction between the simplicity
                  and stupidity, I make the effort and shoot for the former.

                  Michael

                  ---------------------------------------------------
                  Michael Feathers mfeathers@...
                  Object Mentor Inc. www.objectmentor.com
                  Training/Mentoring/Development
                  -----------------------------------------------------
                  "You think you know when you can learn, are more sure when
                  you can write, even more when you can teach, but certain when
                  you can program. " - Alan Perlis
                • Phlip
                  From: ... your ... If you only type just enough to change the code the tiniest amount to satisfy one requirement, you l
                  Message 8 of 20 , Feb 1, 2000
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                    From: <cbrooksbank@...>


                    > If you always write the simplist ( and the most specific ) solution to
                    your
                    > current immediate requirement you will generate problems.

                    If you only type just enough to change the code the tiniest amount to
                    satisfy one requirement, you'l produce bad code.

                    If you also apply OnceAndOnlyOnce and UnitTestFirst (the supporting
                    practices for DTSTTCPW and YAGNI), you can always try to leave the code
                    (and the UnitTests) in their simplest, cleanest state.

                    If you apply any of the 12 canonical XP processes extremely but in
                    isolation from the others you'l get a bad result. Kent's book XPE covers
                    this fully.

                    > The next guy that comes along with a slightly different problem will
                    write his
                    > own specific class.

                    Nope. He'd have broken OAOO. Sacrifice him to an XP principle at their
                    next love fest.

                    Phlip
                    ======= http://users.deltanet.com/~tegan/home.html =======
                  • William Rutiser
                    Some well known aircraft designer once said Simplificate and add lightness . This is one of those things that is easier to say than do. Changes that restrict
                    Message 9 of 20 , Feb 1, 2000
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                      Some well known aircraft designer once said "Simplificate and add
                      lightness". This is one of those things that is easier to say than do.

                      Changes that restrict or constrain future change are less simple in
                      their effects than changes that don't.


                      Bill Rutiser
                      wru@...
                    • Chris Berry
                      Greetings, A buddy of mine just turned me on to an amazing tool for refactoring Java code. It is called Woodenchair (www.woodenchair.com). It allows you to
                      Message 10 of 20 , Feb 1, 2000
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                        Greetings,

                        A buddy of mine just turned me on to an amazing tool for refactoring Java
                        code. It is called Woodenchair (www.woodenchair.com). It allows you to
                        Repackage Mercilessly. It catches *everything*, including even the JavaDocs.
                        And works flawlessly. We just took our semi-large code base (~500 classes)
                        and did a massive restructuring of it (including moving packages, files into
                        different packages, new levels in the hierarchy, etc.) It took about 10
                        minutes. Pretty cool. (I suppose y'all already knew all about it, but just
                        in case... )

                        Cheers,
                        --Chris

                        (And no, I don't have any affiliation w/ Woodenchair ;-)
                      • Phil Goodwin
                        ... Okay, sure. But what does simple mean anyway? Ron once said to use LOC as a metric for simplicity. Is that it? Is it the fewest number of methods?
                        Message 11 of 20 , Feb 1, 2000
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                          "Michael C. Feathers" wrote:
                          >
                          > ----- Original Message -----
                          > From: Joshua Kerievsky <joshua@...>
                          > > Wiki has had a page called DoTheSimplestThingThatCouldPossiblyWork for
                          > well
                          > > over a year now, and the expression has certainly made its way into
                          > the
                          > > culture. However, Kent recently wrote in an email thread I exchanged
                          > with him:
                          > > ----
                          > > Note that I never said "do the simplest thing that could possibly
                          > work".
                          > > That would be stupid. I try to get people to think in terms of
                          > simplicity,
                          > > hence the phrasing "what is the simplest..." It's a mantra.
                          > > ----
                          >
                          > I like how Chet Hedrickson of the C3 team put it on Wiki:
                          > "The rule is, 'Do the simplest thing that could possibly
                          > work', not the most stupid."
                          >
                          > Whenever I can draw the distinction between the simplicity
                          > and stupidity, I make the effort and shoot for the former.
                          >
                          > Michael

                          Okay, sure. But what does 'simple' mean anyway? Ron once said to use LOC
                          as a metric for simplicity. Is that it? Is it the fewest number of
                          methods? Classes? Function points? Is it the simplest to code? To
                          invent? To explain? Does simple mean fast? To me globals are about the
                          simplest scoping and lifetime management strategy, gotos are the
                          simplest control structure and arrays are the simplest collections. It
                          always seems simpler to grow an existing class than to build a new one.
                          So many "simple" things turn out to be headaches later.

                          What I personally have done, with some success, is to START with the
                          simplest thing that could possibly work and use "what seems easiest to
                          program" as my definition of "simple". This is an application of "make
                          it run, make it right, make it fast". After I've written it I test and
                          refactor (making things I touch "right") until it works, and then I
                          continue refactoring until the whole thing is "right". In practice this
                          means that I start out using a lot of primitive tools that are easily
                          manipulated and end up replacing them with tools that are specialized
                          for the kinds of manipulations that I actually end up doing.

                          I don't know if that's the behavior that the advice was supposed to
                          inspire or even if I actually get the final version of the code written
                          any faster. I can say, though, that it gets my relationship with the
                          code started pretty quickly which keeps my interest high and makes
                          things a little more fun.

                          --
                          Phil Goodwin, Java Software, Sun Microsystems, 408-517-6951, or x66951
                        • Chris Berry
                          Greetings, I would like to suggest that the ListServe shorten the email tag it applies to email from this list. What about, say, [xp]. Then we can see more of
                          Message 12 of 20 , Feb 1, 2000
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                            Greetings,

                            I would like to suggest that the ListServe shorten the email tag it applies
                            to email from this list. What about, say, [xp]. Then we can see more of
                            what is important on the Subject line of our email readers.

                            Cheers,
                            -- Chris
                          • Michael C. Feathers
                            ... From: Phil Goodwin ... LOC ... one. ... It seems that there are a lot of forces. Ideally a piece of code should be simple to
                            Message 13 of 20 , Feb 1, 2000
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                              ----- Original Message -----
                              From: Phil Goodwin <phil.goodwin@...>
                              > Okay, sure. But what does 'simple' mean anyway? Ron once said to use
                              LOC
                              > as a metric for simplicity. Is that it? Is it the fewest number of
                              > methods? Classes? Function points? Is it the simplest to code? To
                              > invent? To explain? Does simple mean fast? To me globals are about the
                              > simplest scoping and lifetime management strategy, gotos are the
                              > simplest control structure and arrays are the simplest collections. It
                              > always seems simpler to grow an existing class than to build a new
                              one.
                              > So many "simple" things turn out to be headaches later.

                              It seems that there are a lot of forces. Ideally a piece of code
                              should be simple to understand, simple to change, and simple to
                              code.

                              One thing I've discovered when trying to do what Kent and
                              Ron talk about is that good object factoring allows me to strike a
                              balance between those three things. For instance, when you
                              extract a class, you get to introduce a name which conveys intent
                              a bit more. If the extraction was really warranted, two classes are
                              easier to understand on their own and together after the extraction.
                              Each resulting class is also closed under more changes. But
                              isn't it easier to code the larger class? Yes, but if it costs too much
                              on the other two prongs of simplicity, you refactor.

                              I just think that the OO flavor of simplicity is different. Sometimes
                              I look at some very clear procedural code and realize that it
                              conveys intent very well, but it would fail on other two prongs
                              of simplicity. Things like 'replace conditional with polymorphism'
                              may not be too simple from the procedural point of view, but
                              once changeability and dependency management are taken
                              into account, it is a clear win. Simple designs are easily
                              extended. I remember when I read Bob Martin's description
                              of the Dependency Inversion Principle years ago, I realized
                              this is why objects are different. Each interface is a point of
                              variation. You can have a great deal of flexibility without
                              making all sorts of "hooks."

                              > What I personally have done, with some success, is to START with the
                              > simplest thing that could possibly work and use "what seems easiest to
                              > program" as my definition of "simple". This is an application of "make
                              > it run, make it right, make it fast". After I've written it I test and
                              > refactor (making things I touch "right") until it works, and then I
                              > continue refactoring until the whole thing is "right". In practice
                              this
                              > means that I start out using a lot of primitive tools that are easily
                              > manipulated and end up replacing them with tools that are specialized
                              > for the kinds of manipulations that I actually end up doing.

                              Yeah, I do that too. It is a great way to get started. I usually stick
                              a spike in the ground.. some interface that I can test behind and
                              then write brute force code that I can refactor into better
                              structure as it occurs to me.


                              Michael

                              ---------------------------------------------------
                              Michael Feathers mfeathers@...
                              Object Mentor Inc. www.objectmentor.com
                              Training/Mentoring/Development
                              -----------------------------------------------------
                              "You think you know when you can learn, are more sure when
                              you can write, even more when you can teach, but certain when
                              you can program. " - Alan Perlis
                            • Phil Goodwin
                              ... My friend who is receiving XP tutoring from Don Robert says that they are literally programming the simplest thing that could possibly make the simplest of
                              Message 14 of 20 , Feb 1, 2000
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                                At 06:01 PM 2/1/00 -0500, Michael C. Feathers wrote:
                                >----- Original Message -----
                                >From: Phil Goodwin <phil.goodwin@...>
                                > > Okay, sure. But what does 'simple' mean anyway?

                                >It seems that there are a lot of forces. Ideally a piece of code
                                >should be simple to understand, simple to change, and simple to
                                >code.
                                >
                                >One thing I've discovered when trying to do what Kent and
                                >Ron talk about is that good object factoring allows me to strike a
                                >balance between those three things. For instance, when you
                                >extract a class, you get to introduce a name which conveys intent
                                >a bit more. If the extraction was really warranted, two classes are
                                >easier to understand on their own and together after the extraction.
                                >Each resulting class is also closed under more changes. But
                                >isn't it easier to code the larger class? Yes, but if it costs too much
                                >on the other two prongs of simplicity, you refactor.

                                My friend who is receiving XP tutoring from Don Robert says that they are
                                literally programming the simplest thing that could possibly make the
                                simplest of tests work. That's simplest as in simplest to program and also
                                the simplest problem. While listening to him talk about it tonight the
                                ambiguity of the notion of simplicity fell away. What I got was essentially
                                that if the initial code had any chance at all of being the least bit
                                interesting it was too complicated. All the interesting/complex stuff they
                                were doing was coming from refactoring.

                                >I just think that the OO flavor of simplicity is different. Sometimes
                                >I look at some very clear procedural code and realize that it
                                >conveys intent very well, but it would fail on other two prongs
                                >of simplicity. Things like 'replace conditional with polymorphism'
                                >may not be too simple from the procedural point of view, but
                                >once changeability and dependency management are taken
                                >into account, it is a clear win. Simple designs are easily
                                >extended. I remember when I read Bob Martin's description
                                >of the Dependency Inversion Principle years ago, I realized
                                >this is why objects are different. Each interface is a point of
                                >variation. You can have a great deal of flexibility without
                                >making all sorts of "hooks."

                                Flexibility and understandability are forces that are at odds with
                                simplicity. I think that simplicity is a starting point and is used as a
                                currency with which to buy expressiveness and flexibility. You buy
                                expressiveness after you've got something to work and are about to leave it
                                behind and you buy flexibility just as it's needed. At least that's my
                                understanding for today.

                                Phil
                              • Kent Beck
                                Let s review the rules. In order: 1. Run all the test cases 2. Communicate everything you need to communicate 3. No duplication 4. Fewest possible classes and
                                Message 15 of 20 , Feb 2, 2000
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                                  Let's review the rules. In order:
                                  1. Run all the test cases
                                  2. Communicate everything you need to communicate
                                  3. No duplication
                                  4. Fewest possible classes and methods

                                  If you did something simple, it meets the rules. If the next person coming
                                  along copies some of your code into their class, it doesn't meet the rules.
                                  Don't do that.

                                  Martin tells me that my definition of "simple" isn't clear. I think perhaps
                                  the problem is that I shouldn't use the word "simple". Something like
                                  "normalized" or "factored" is better, but it doesn't capture the
                                  communication aspect.

                                  Kent
                                • Michael C. Feathers
                                  ... From: Phil Goodwin ... Sometimes ... a ... leave it ... Yes, there are all sorts of definitions of simplicity. I like to take the
                                  Message 16 of 20 , Feb 2, 2000
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                                    ----- Original Message -----
                                    From: Phil Goodwin <pgoodwin@...>
                                    > At 06:01 PM 2/1/00 -0500, Michael C. Feathers wrote:
                                    > >I just think that the OO flavor of simplicity is different.
                                    Sometimes
                                    > >I look at some very clear procedural code and realize that it
                                    > >conveys intent very well, but it would fail on other two prongs
                                    > >of simplicity. Things like 'replace conditional with polymorphism'
                                    > >may not be too simple from the procedural point of view, but
                                    > >once changeability and dependency management are taken
                                    > >into account, it is a clear win. Simple designs are easily
                                    > >extended. I remember when I read Bob Martin's description
                                    > >of the Dependency Inversion Principle years ago, I realized
                                    > >this is why objects are different. Each interface is a point of
                                    > >variation. You can have a great deal of flexibility without
                                    > >making all sorts of "hooks."
                                    >
                                    > Flexibility and understandability are forces that are at odds with
                                    > simplicity. I think that simplicity is a starting point and is used as
                                    a
                                    > currency with which to buy expressiveness and flexibility. You buy
                                    > expressiveness after you've got something to work and are about to
                                    leave it
                                    > behind and you buy flexibility just as it's needed. At least that's my
                                    > understanding for today.

                                    Yes, there are all sorts of definitions of simplicity. I like to take
                                    the broad one, because I've noticed that 'simple to understand',
                                    'simple to implement', and 'simple to change' all feed into each
                                    other when I am going on the right track. The Venn diagram
                                    has such a large intersection that I don't feel that one
                                    happens at much expense to the others. Maybe I'm not
                                    being introspective enough on this point.

                                    That said, I agree about starting with 'simple to implement.'
                                    Of the three, though, I like to shoot for 'simple to understand'
                                    because it offers the most bang for the buck.


                                    Michael

                                    ---------------------------------------------------
                                    Michael Feathers mfeathers@...
                                    Object Mentor Inc. www.objectmentor.com
                                    Training/Mentoring/Development
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                                    "You think you know when you can learn, are more sure when
                                    you can write, even more when you can teach, but certain when
                                    you can program. " - Alan Perlis
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