十年学会程序设计

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Why is everyone in such a rush?

Walk into any bookstore, and you'll see how to Teach Yourself Javain 7 Days alongside endless variations offering to teach VisualBasic, Windows, the Internet, and so on in a few days or hours. I didthe following power search at Amazon.com

:

     pubdate: after 1992 and title: days and
      (title: learn or title: teach yourself)

and got back 248 hits. The first 78 were computer books (number 79was LearnBengali in 30 days). I replaced "days" with "hours"and got remarkably similar results: 253 more books, with 77 computerbooks followed by TeachYourself Grammar and Style in 24 Hours at number 78. Out ofthe top 200 total, 96% were computer books.

The conclusion is that either people are in a big rush to learnabout computers, or that computers are somehow fabulously easier tolearn than anything else. There are no books on how to learnBeethoven, or Quantum Physics, or even Dog Grooming in a few days.Felleisen et al.give a nod to this trend in their book How to Design Programs, when they say"Bad programming is easy. Idiots can learn it in 21 days,even if they are dummies.

Let's analyze what a title like Learn C++ in Three Dayscould mean:

• Learn: In 3 days you won't have time to write severalsignificant programs, and learn from your successes and failures withthem. You won't have time to work with an experienced programmer andunderstand what it is like to live in a C++ environment. In short, youwon't have time to learn much. So the book can only be talking about asuperficial familiarity, not a deep understanding. As Alexander Pope said,a little learning is a dangerous thing.

   

• C++: In 3 days you might be able to learn some of the syntax ofC++ (if you already know another language), but you couldn'tlearn much about how to use the language. In short, if you were, say, aBasic programmer, you could learn to write programs in the style ofBasic using C++ syntax, but you couldn't learn what C++ isactually good (and bad) for. So what's the point? AlanPerlis once said: "A language that doesn't affect the way youthink about programming, is not worth knowing". One possible point isthat you have to learn a tiny bit of C++ (or more likely, somethinglike JavaScript or Flash's Flex) because you need to interface with anexisting tool to accomplish a specific task. But then you're notlearning how to program; you're learning to accomplish that task.

   

• in Three Days: Unfortunately, this is not enough, as the nextsection shows.

Teach Yourself Programming in Ten Years

Researchers (Bloom(1985), Bryan & Harter (1899), Hayes(1989), Simmon & Chase (1973)) have shown ittakes about ten years to develop expertise in any of a wide variety ofareas, including chess playing, music composition, telegraphoperation, painting, piano playing, swimming, tennis, and research inneuropsychology and topology. The key is deliberativepractice: not just doing it again and again, but challenging yourselfwith a task that is just beyond your current ability, trying it,analyzing your performance while and after doing it, and correctingany mistakes. Then repeat. And repeat again. There appear to be noreal shortcuts: even Mozart, who was a musical prodigy at age 4, took13 more years before he began to produce world-class music. Inanother genre, the Beatles seemed to burst onto the scene with astring of #1 hits and an appearance on the Ed Sullivan show in 1964.But they had been playing small clubs in Liverpool and Hamburg since1957, and while they had mass appeal early on, their first greatcritical success, Sgt. Peppers, was released in 1967. MalcolmGladwell reports that a study of students at the Berlin Academy ofMusic compared the top, middle, and bottom third of the class andasked them how much they had practiced:

Everyone, from all three groups, started playing at roughly the sametime - around the age of five. In those first few years, everyonepractised roughly the same amount - about two or three hours aweek. But around the age of eight real differences started toemerge. The students who would end up as the best in their class beganto practise more than everyone else: six hours a week by age nine,eight by age 12, 16 a week by age 14, and up and up, until by the ageof 20 they were practising well over 30 hours a week. By the age of20, the elite performers had all totalled 10,000 hours of practiceover the course of their lives. The merely good students had totalled,by contrast, 8,000 hours, and the future music teachers just over4,000 hours.

So it may be that 10,000 hours, not 10 years, is the magic number.Samuel Johnson (1709-1784) thought ittook longer: "Excellence in any department can beattained only by the labor of a lifetime; it is not to be purchased ata lesser price." And Chaucer (1340-1400) complained "the lyf so short, the craftso long to lerne." Hippocrates (c. 400BC) is known for the excerpt "ars longa,vita brevis", which is part of the longer quotation "Ars longa, vitabrevis, occasio praeceps, experimentum periculosum, iudiciumdifficile", which in English renders as "Life is short, [the] craftlong, opportunity fleeting, experiment treacherous, judgmentdifficult." Although in Latin, ars can mean either art orcraft, in the original Greek the word "techne" can only mean "skill", not "art".

Here's my recipe for programming success:

• Get interested in programming, and do some because it is fun. Make surethat it keeps being enough fun so that you will be willing to put in ten years.

   

• Talk to other programmers; read other programs. This is more importantthan any book or training course.

   

• Program. The best kind of learning is learningby doing. To put it more technically, "the maximal level ofperformance for individuals in a given domain is not attainedautomatically as a function of extended experience, but the level ofperformance can be increased even by highly experienced individuals asa result of deliberate efforts to improve." (p. 366)and "the most effective learning requires a well-defined task with anappropriate difficulty level for the particular individual,informative feedback, and opportunities for repetition and correctionsof errors." (p. 20-21) The book Cognition in Practice: Mind, Mathematics, and Culture in EverydayLife is an interesting reference for this viewpoint.

   

• If you want, put in four years at a college (or more at agraduate school). This will give you access to some jobs that requirecredentials, and it will give you a deeper understanding of the field,but if you don't enjoy school, you can (with some dedication) getsimilar experience on the job. In any case, book learning alone won'tbe enough. "Computer science education cannot make anybody an expertprogrammer any more than studying brushes and pigment can makesomebody an expert painter" says Eric Raymond, author of The NewHacker's Dictionary. One of the best programmers I ever hired hadonly a High School degree; he's produced a lot of great software, has his own news group, and made enough in stock options to buy his own nightclub.
• Work on projects with other programmers. Be the best programmeron some projects; be the worst on some others. When you're the best,you get to test your abilities to lead a project, and to inspireothers with your vision. When you're the worst, you learn what themasters do, and you learn what they don't like to do (because theymake you do it for them).

   

• Work on projects after other programmers. Be involved inunderstanding a program written by someone else. See what it takes tounderstand and fix it when the original programmers are notaround. Think about how to design your programs to make it easier forthose who will maintain it after you.

   

• Learn at least a half dozen programming languages. Include onelanguage that supports class abstractions (like Java or C++), one thatsupports functional abstraction (like Lisp or ML), onethat supports syntactic abstraction (like Lisp), onethat supports declarative specifications (like Prolog or C++templates), one that supports coroutines (like Icon or Scheme), andone that supports parallelism (like Sisal).

   

• Remember that there is a "computer" in "computer science". Knowhow long it takes your computer to execute an instruction, fetch aword from memory (with and without a cache miss), read consecutive words from disk, and seek to a new location on disk. (Answers here.)

   

• Get involved in a languagestandardization effort. It could be the ANSI C++ committee, or itcould be deciding if your local coding style will have 2 or 4 spaceindentation levels. Either way, you learn about what other peoplelike in a language, how deeply they feel so, and perhaps even a littleabout why they feel so.

   

• Have the good sense to get off the language standardization effort asquickly as possible.

With all that in mind, its questionable how far you can get just bybook learning. Before my first child was born, I read all the HowTo books, and still felt like a clueless novice. 30 Months later,when my second child was due, did I go back to the books for arefresher? No. Instead, I relied on my personal experience, whichturned out to be far more useful and reassuringto me than the thousands of pages writtenby experts.

Fred Brooks, in his essay No Silver Bullet identified a three-part plan for finding greatsoftware designers:

1. Systematically identify top designers as early as possible.

    

2. Assign a career mentor to be responsible for the development of the prospect and carefully keep a career file.

    

3. Provide opportunities for growing designers to interact and stimulate each other.

    

This assumes that some people already have the qualities necessary forbeing a great designer; the job is to properly coax them along. AlanPerlis put it more succinctly: "Everyone can be taught to sculpt:Michelangelo would have had to be taught how not to. So it is with thegreat programmers".

So go ahead and buy that Java book; you'll probably get some use out of it.But you won't change your life, or your real overall expertise as aprogrammer in 24 hours, days, or even months.

 

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References

Bloom, Benjamin (ed.) Developing Talent in Young People, Ballantine, 1985.

Brooks, Fred, No Silver Bullets, IEEE Computer, vol. 20, no. 4, 1987, p. 10-19.

Bryan, W.L. & Harter, N. "Studies on the telegraphic language:The acquisition of a hierarchy of habits. Psychology Review,1899, 8, 345-375

Hayes, John R., Complete Problem Solver Lawrence Erlbaum, 1989.

Chase, William G. & Simon, Herbert A. "Perception in Chess"Cognitive Psychology, 1973, 4, 55-81.

Lave, Jean, Cognition in Practice: Mind, Mathematics, and Culture in EverydayLife, Cambridge University Press, 1988.

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Answers

Approximate timing for various operations on a typical 1GHz PC in 2001:

execute single instruction 1 nanosec = (1/1,000,000,000) secfetch word from L1 cache memory 2 nanosecfetch word from main memory 10 nanosec fetch word from consecutive disk location 200 nanosecfetch word from new disk location (seek) 8,000,000 nanosec = 8 millisec

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Appendix: Language Choice

Several people have asked what programming language they should learn first.There is no one answer, but consider these points:

 

• Use your friends. When asked "what operating system shouldI use, Windows, Unix, or Mac?", my answer is usually: "use whateveryour friends use." The advantage you get from learning from yourfriends will offset any intrinsic difference between OS, orbetween programming languages. Also consider your future friends:the community of programmers that you will be a part of if youcontinue. Does your chosen language have a large growing communityor a small dying one? Are there books, web sites, and online forumsto get answers from? Do you like the people in those forums?
• Keep it simple. Programming languages such as C++and Java are designed for professional development by large teams ofexperienced programmers who are concerned about the run-time efficiency oftheir code.As a result, these languages have complicated parts designed for these circumstances.You're concerned with learning to program. You don't need that complication.You want a language that was designed to be easy to learn and remember by asingle new programmer.
• Play. Which way would you rather learn to play the piano: thenormal, interactive way, in which you hear each note as soon as you hit a key,or "batch" mode, in which you only hear the notes after you finish a whole song?Clearly, interactive mode makes learning easier for the piano, and also for programming. Insist on a language with an interactive mode and use it.

Given these criteria, my recommendations for a first programminglanguage would be Python orScheme. But yourcircumstances may vary, and there are other good choices. If yourage is a single-digit, you might preferAlice or Squeak (older learners might also enjoy these). The importantthing is that you choose and get started.

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Appendix: Books and Other Resources

Several people have asked what books and web pages they should learnfrom. I repeat that "book learning alone won't be enough" but I canrecommend the following:

 

• Scheme: Structure andInterpretation of Computer Programs (Abelson & Sussman) isprobably the best introduction to computer science, and it doesteach programming as a way of understanding the computer science. You can see online videos of lectures on this book, as well as the complete text online. The book ischallenging and will weed out some people who perhaps could besuccessful with another approach.
• Scheme:How toDesign Programs (Felleisen et al.) is one of the best bookson how to actually design programs in an elegant and functional way.
• Python: Python Programming:An Intro to CS (Zelle) is a good introduction using Python.
• Python: Severalonline tutorials are available at Python.org.
• Oz: Concepts,Techniques, and Models of Computer Programming (Van Roy & Haridi)is seen by some as the modern-day successor to Abelson & Sussman.It is a tour through the big ideas of programming, covering a widerrange than Abelson & Sussman while being perhaps easier to read andfollow. It uses a language, Oz, that is not widely known but serves asa basis for learning other languages.<

 

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Notes

T. Capey points out that the Complete Problem Solver page on Amazon now has the "Teach Yourself Bengali in 21 days" and "Teach Yourself Grammar and Style" books under the "Customers who shopped for this item also shopped for these items" section. I guess that a large portion of the people who look at that book are coming from this page.Thanks to Ross Cohen for help with Hippocrates.