Tài liệu Seven Languages in Seven Weeks pptx

What Readers Are Saying About

Seven Languages in Seven Weeks

Knowingmultipleparadigmsgreatlyinfluencesourdesignabilities,so

I’malwaysonthelookoutforgoodbooksthat’llhelpmelearnthem.

Thisbooknicelybringsprominentparadigmstogether.Brucehas

experiencelearningandusingmultiplelanguages.Nowyoucangain

fromhisexperiencethroughthisbook.Ihighlyrecommendit.

Dr. Venkat Subramaniam

Award-winningauthorandfounder,AgileDeveloper,Inc.

Asaprogrammer,theimportanceofbeingexposedtonewprogram￾minglanguages,paradigms,andtechniquescannotbeoverstated.

Thisbookdoesamarvelousjobofintroducingsevenimportantand

diverselanguagesinaconcise—butnontrivial—manner,revealing

theirstrengthsandreasonsforbeing.Thisbookisakintoadim-sum

buffetforanyprogrammerwhoisinterestedinexploringnewhorizons

orevaluatingemerginglanguagesbeforecommittingtostudyingone

inparticular.

Antonio Cangiano

Softwareengineerandtechnicalevangelist,IBM

Fastenyourseatbelts,becauseyouareinforafast-pacedjourney.

Thisbookispackedwithprogramming-language-learningaction.

Bruceputsitallontheline,andtheresultisanengaging,reward￾ingbookthatpassionateprogrammerswillthoroughlyenjoy.Ifyou

lovelearningnewlanguages,ifyouwanttochallengeyourmind,if

youwanttotakeyourprogrammingskillstothenextlevel—thisbook

isforyou.Youwillnotbedisappointed.

Frederic Daoud

Author, Stripes...andJavaWebDevelopmentIsFunAgain and

GettingStartedwithApacheClick

Doyouwantsevenkickstartsintolearningyour“languageofthe

year”?Doyouwantyourthinkingchallengedaboutprogrammingin

general?Looknofurtherthanthisbook.Ipersonallywastakenback

intimetomyundergraduatecomputersciencedays,coastingthrough

myprogramminglanguagessurveycourse.Thedifferenceisthat

Brucewon’tletyoucoastthroughthiscourse!Thisisn’taleisurely

read—you’llhavetoworkthisbook.Ibelieveyou’llfinditbothmind￾blowingandintenselypracticalatthesametime.

Matt Stine

Groupleader,ResearchApplicationDevelopmentatSt.Jude

Children’sResearchHospital

IspentmostofmytimeasacomputersciencesstudentsayingIdidn’t

wanttobeasoftwaredeveloperandthenbecameoneanyway. Seven

LanguagesinSevenWeeks expandedmywayofthinkingaboutprob￾lemsandremindedmewhatIloveaboutprogramming.

Travis Kaspar

Softwareengineer,NorthropGrumman

Ihavebeenprogrammingfor25yearsinavarietyofhardwareand

softwarelanguages.Afterreading SevenLanguagesinSevenWeeks ,I

amstartingtounderstandhowtoevaluatelanguagesfortheirobjec￾tivestrengthsandweaknesses.Moreimportantly,IfeelasifIcould

pickoneofthemtoactuallygetsomeworkdone.

Chris Kappler

Seniorscientist,RaytheonBBNTechnologies

SevenLanguagesinSevenW eeks

APragmaticGuidetoLearning

ProgrammingLanguages

BruceA.Tate

The Pragmatic Bookshelf

Raleigh,NorthCarolina Dallas,Texas

Manyofthedesignationsusedbymanufacturersandsellerstodistinguishtheirprod￾uctsareclaimedastrademarks.Wherethosedesignationsappearinthisbook,andThe

Pragmatic Programmers, LLCwas aware of a trademark claim,thedesignationshave

beenprintedininitial capitallettersor inall capitals.ThePragmaticStarterKit,The

PragmaticProgrammer,PragmaticProgramming,PragmaticBookshelfandthelinking g

devicearetrademarksofThePragmaticProgrammers,LLC.

Every precaution was taken in the preparation of this book. However, the publisher

assumesnoresponsibilityforerrorsoromissions,orfordamagesthatmayresultfrom

theuseofinformation(includingprogramlistings)containedherein.

Our Pragmatic courses, workshops, and other products can help youand your team

createbettersoftwareandhavemorefun.Formoreinformation,aswellasthelatest

Pragmatictitles,pleasevisitusat http://www.pragprog.com.

Theteamthatproducedthisbookincludes:

Editor: JackieCarter

Indexing: PotomacIndexing,LLC

Copyedit: KimWmi pset

Layout: StevePeter

Production: JanetFurlow

Customersupport: EllieCallahan

International: JulietBenda

Copyright © 2010PragmaticProgrammers,LLC.

Allrightsreserved.

Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmit￾ted,inanyform,orbyanymeans,electronic,mechanical,photocopying,recording,or

otherwise,withoutthepriorconsentofthepublisher.

PrintedintheUnitedStatesofAmerica.

ISBN-10:1-934356-59-X

ISBN-13:978-1-934356-59-3

Printedonacid-freepaper.

P1.0printing,October2010

Versoin:2010-10-28

Contents

Dedication 9

Acknowledgments 11

Foreword 14

1 Introduction 17

1.1 MethodtotheMadness . . . . . . . . . . . . . . . . . . 17

1.2 TheLanguages . . . . . . . . . . . . . . . . . . . . . . . 19

1.3 BuyThisBook. . . . . . . . . . . . . . . . . . . . . . . . 21

1.4 Don’tBuyThisBook . . . . . . . . . . . . . . . . . . . . 22

1.5 AFinalCharge. . . . . . . . . . . . . . . . . . . . . . . . 24

2 Ruby 25

2.1 QuickHistory . . . . . . . . . . . . . . . . . . . . . . . . 26

2.2 Day1:FindingaNanny . . . . . . . . . . . . . . . . . . 28

2.3 Day2:FloatingDownfromtheSky . . . . . . . . . . . 35

2.4 Day3:SeriousChange. . . . . . . . . . . . . . . . . . . 48

2.5 WrappnigUpRuby . . . . . . . . . . . . . . . . . . . . . 56

3 Io 60

3.1 IntroducingIo . . . . . . . . . . . . . . . . . . . . . . . . 60

3.2 Day1:SkippingSchool,HangingOut . . . . . . . . . . 61

3.3 Day2:TheSausageKing . . . . . . . . . . . . . . . . . 74

3.4 Day3:TheParadeandOtherStrangePlaces . . . . . . 83

3.5 WrappnigUpIo . . . . . . . . . . . . . . . . . . . . . . . 92

4 Prolog 95

4.1 AboutProlog . . . . . . . . . . . . . . . . . . . . . . . . . 96

4.2 Day1:AnExcellentDriver. . . . . . . . . . . . . . . . . 97

4.3 Day2:FifteenMinutestoWapner . . . . . . . . . . . . 109

4.4 Day3:BlowingUpVegas . . . . . . . . . . . . . . . . . . 120

4.5 WrappnigUpProlog. . . . . . . . . . . . . . . . . . . . . 132

CONTENTS 8

5 Scala 135

5.1 AboutScala . . . . . . . . . . . . . . . . . . . . . . . . . 135

5.2 Day1:TheCastleontheHill . . . . . . . . . . . . . . . 139

5.3 Day2:ClippingBushesandOtherNewTricks . . . . . 153

5.4 Day3:CuttingThroughtheFluff. . . . . . . . . . . . . 167

5.5 WrappnigUpScala . . . . . . . . . . . . . . . . . . . . . 176

6 Erlang 181

6.1 IntroducingErlang . . . . . . . . . . . . . . . . . . . . . 181

6.2 Day1:AppearingHuman . . . . . . . . . . . . . . . . . 185

6.3 Day2:ChangingForms . . . . . . . . . . . . . . . . . . 195

6.4 Day3:TheRedPill . . . . . . . . . . . . . . . . . . . . . 207

6.5 WrappnigUpErlang . . . . . . . . . . . . . . . . . . . . 219

7 Clojure 223

7.1 IntroducingClojure. . . . . . . . . . . . . . . . . . . . . 224

7.2 Day1:Training Luke . . . . . . . . . . . . . . . . . . . . 225

7.3 Day2:YodaandtheForce. . . . . . . . . . . . . . . . . 243

7.4 Day3:AnEyeforEvil . . . . . . . . . . . . . . . . . . . 256

7.5 WrappnigUpClojure . . . . . . . . . . . . . . . . . . . . 264

8 Haskell 268

8.1 IntroducingHaskell. . . . . . . . . . . . . . . . . . . . . 268

8.2 Day1:Logical . . . . . . . . . . . . . . . . . . . . . . . . 269

8.3 Day2:Spock’sGreatStrength . . . . . . . . . . . . . . 285

8.4 Day3:TheMindMeld . . . . . . . . . . . . . . . . . . . 294

8.5 WrappnigUpHaskell. . . . . . . . . . . . . . . . . . . . 309

9 Wrap-Up 313

9.1 ProgrammingModels . . . . . . . . . . . . . . . . . . . . 313

9.2 Concurrency. . . . . . . . . . . . . . . . . . . . . . . . . 317

9.3 ProgrammingConstructs . . . . . . . . . . . . . . . . . 319

9.4 FindingYourVocie . . . . . . . . . . . . . . . . . . . . . 321

A Bibliography 322

Index 323

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Dedication

ThefivemonthsfromDecember2009throughApril2010wereamong

themostdifficultofmylife.Mybrother,notyet47yearsold,hademer￾gencybypasssurgery.Noonehadanycluethatanythingwaswrong

atall.(He came throughthe surgerywithoutfurther incidentandis

doingwell.)InlateMarch,mysisterwasdiagnosedwithbreastcancer.

ThebiggestshockofallcameinearlyMarch.Mymotherwasdiagnosed

withterminalcancer.Afewshortweekslater,shewasgone.

As youwouldexpect,Iamleftto strugglewiththe grief ofajarring

and unexpected loss because of a brutally efficient disease. I would

notbehumanotherwise.Butstrangely,thisexperiencehasnotbeen

anentirelynegative one.You see,mymotherwas atpeacewiththe

remarkablelifeshelived,herrelationshipswithherfamilywerestrong

andfulfilling,andshewas exactlywhere shewantedtobewithher

faith.

Lynda Lyle Tateputhercreativeenergyintopaintingwithwatercolors.

ShesharedherartprimarilythroughherMadisonAvenueArtGallery

andherclasses.BeforeIlefthome,Ihadtheopportunitytotakeafew

lessonsfromher.Forsomeonefromatechnicalprofession,theexperi￾encewasalwaysalittledisorienting.Iwouldvisualizethemasterpiece

onmyblankcanvas.Astheactualimagetookshape,itdriftedfurther

andfurtherfrommyoriginalvision.WhenIdespairedthatthingswere

beyondmyability tofix,Momlookedovermy shoulderandtoldme

whatshesaw.Afterafewflicksofhertalentedwristaddeddarksto

accentuatedepthandhighlightstoaddclarityanddetail,Iwouldreal￾izethatIhadnotbeentoofarastrayatall.Itjusttookagiftedtouchto

bringbackmycreationfromthebrinkofdisaster.Then,Iwouldthrow

myexcitedarmsupinvictoryandtelleveryoneintheclassaboutthis

thingIhadcreated,notyetrealizingthateachmemberoftheclasswas

goingthroughtheirownprivateburstofjoy.

DEDICATION 10

Afteralittlewhile,IlearnedthatMomwasworkingonanothercanvas

as well. Throughher churchand throughher profession, she’d find

brokenpeople.Encounteringalostspousehereoratroubledmarriage

there,mymotherwouldbringthemintoclasswhereshewouldusethe

paintandpapertoslightlyopenadoorthathadbeenslammedshut.

Aswespentour lastweektogether,personafterpersonwouldcome

throughherroomdevastatedatthethoughtoflosingtheirteacher,but

Mom would tellthe perfectjoke or offer the right word of kindness,

comforting thosewhocame tocomforther.Igottomeetthehuman

canvaseswhohadbeenputrightbythemasterandgoneontodogreat

things.Itwasahumblingexperience.

When Itold my mother thatI would dedicate this book to her, she

said that she would like that, but shehadnothing to do withcom￾puters.Thatistrueenough.TheverythoughtofWnidowswouldleave

herhelpless.ButMom,youhavehadeverythingtodowith me.Your

well-timedwordsofencouragementinspiredme,yourloveofcreativity

shapedme,andyourenthusiasmandloveoflifeguidemeevennow.

AsIthinkabouttheseexperiences,Ican’thelpbutfeelalittlebetter

andalittlestrongerbecauseI,too,amacanvasshapedbythemaster.

ThisbookisdedicatedwithlovetoLynda Lyle Tate,1936–2010.

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Acknowledgments

ThisisthemostdemandingbookIhaveeverwritten.It’salsothemost

rewarding.Thepeoplewhohaveofferedtohelpinvariouswayshave

madeitso.Thanksfirstandforemosttomyfamily.KaylaandJulia,

yourwritingamazesme.You can’tyetimaginewhatyoucanaccom￾plish.Maggie,youaremyjoyandinspiration.

Inthe Ruby community,thanks to Dave Thomas for turning me on

to the language thatturned my career upside down and helped me

havefunagain.ThanksalsotoMatzforyourfriendshipandyouroffer

toshareyour thoughtswithmyreaders.You invitedmetoJapanto

visittheplacewhereRubywasborn,andthatexperienceinspiredme

muchmorethanyouwilleverknow.ToCharlesNutter,EvanPhoenix,

andTim Bray,thanksfortheconversationsabouttopicsinthisbook

thatmusthaveseemedtiresomebuthelpedmerefineandshapethe

message.

IntheIocommunity,thankstoJeremyTregunna forhelpingmeget

pluggedinandsharingsomecoolexamplesforthebook.Yourreviews

were among the best. They were timely and helped build a much

stronger chapter. Steve Dekorte, you’ve created something special,

whetherornotthemarketplaceeverrecognizesitasso.Theconcur￾rencyfeaturesrock,andthelanguagehasintrinsicbeauty.Icandef￾initely appreciatehowmuchofthis language feels right. Thanks for

helping this neophyte debug his installation. Thanks also for your

thoughtfulreviewsandyourinterviewthathelpedmecapturethees￾senceofIo.Youcapturedtheimaginationofthebetareadersandcre￾atedthefavoritelanguageofmanyofthem.

In the Prolog community, thanks to Brian Tarbox for sharing your

remarkableexperiencewithmyreaders.Thedolphinprojects,featured

onNova,certainlyaddadramaticflairtothePrologchapter.Special

thanks go to Joe Armstrong. You can see how much your feedback

shapedthechapterandtheoverallbook.Thanksalsoforcontributing

ACKNOWLEDGMENTS 12

yourmap-coloringexampleandyourideasforAppend.Theywerethe

rightexamplesdeliveredattherighttime.

IntheScalacommunity,thankstomygoodfriendVenkat Subrama￾niam.Your Scalabookisbothrichandunderstandable.Ileanedon

itheavily.I greatly appreciate your review and the little bits ofhelp

that you offered along the way. Those little bits of your time saved

me tremendous anguish and let me focus on the task of teaching.

ThanksalsotoMartinOderskyforhelpingthisstrangerbysharingyour

thoughtswithmyreaders.Scalatakesauniqueandbraveapproach

tointegratingfunctionalprogrammingparadigmswithobject-oriented

paradigms.Youreffortsaregreatlyappreciated.

IntheErlangcommunity,IagainthankJoeArmstrong.Yourkindness

andenergyhavehelpedmeformtheideasinthisbook.Your tireless

promotionofthewaydistributed,fault-tolerantsystemsshouldbebuilt

is working. More than any other idea in any other language in this

book,Erlang’s“Letitcrash”philosophymakessensetome.Ihopeto

seethoseideasmorebroadlyadopted.

IntheClojurecommunity,thankstoStuartHallowayforyourreviews

and ideas that forced me to work harder to bring a better book to

myreaders.Your insights intoClojureandyour instinctshelpedme

understandwhatwasimportant.Yourbookwasalsohugelyinfluential

intheClojurechapterandactuallychangedthewayIattackedsome

problemsinotherchaptersaswell.Yourapproachinyourconsulting

practiceisgreatlyappreciated.Your’ebringingmuch-neededsimplicity

andproductivitytothisindustry.ThanksalsotoRichHickeyforyour

thoughtfulideasonthecreationofthelanguageandwhatitmeansto

beaLispdialect.SomeideasinClojureareintenselyradicalandyet

sopractical.Congratulations.Youv’efoundawaytomakeLisprevolu￾tionary.Again.

Inthe Haskell community,thanks toPhillipWadelr for the opportu￾nitytolookinsidetheprocessthatcreatedHaskell.We shareapas￾sion for teaching, and you’re very good atit. Thanks also to Simon

Peyton-Jones.Ienjoyedworkingthroughyour interview,theinsights

youadded,andtheuniqueperspectiveyoubroughttothesereaders.

Thereviewersdidanoutstandingjobwiththisbook.ThankstoVladi￾mirG.Ivanovic,CraigRiecke,PaulButcher,FredDaoud,AaronBedra,

DavidEisinger,AntonioCangiano,andBrianTarbox.You formedthe

most effective review team I’ve ever worked with. The book is much

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ACKNOWLEDGMENTS 13

stronger for it.Iknowthat reviewingabookatthis levelofdetailis

thankless,demandingwork.Thoseofuswhostillliketechnicalbooks

thankyou.Thepublishingbusinesscouldnotexistwithoutyou.

Ialsowanttothankthoseofyouwhosharedyourideasaboutlanguage

choiceandprogrammingphilosophy.Atvarioustimes,NealFord,John

Heintz,MikePerham,andIanWarshakmadesignificantcontributions.

ThesekindsofconversationsmademelooksmarterthanIreallyam.

Betareaders,thankyouforreadingthebookandkeepingmeworking.

Yourcommentshaveshownmethatagoodnumberofyouareworking

throughthelanguagesratherthancasuallyskimming.I’vechangedthe

bookbasedonhundredsofcommentssofarandexpecttodoevenmore

throughoutthelifeofthebook.

Finally,to the teamatthePragmaticBookshelf,I offermy sincerest

gratitude.DaveThomasandAndyHunt,youhavehadanincalculable

impactonmycareerasaprogrammerandagainasanauthor.This

publishingplatformhasmadewritingviableagainforme.We cantake

abooklikethisonethatmightnotbeasattractivetothemassmarket

andmakeitfinanciallyworthwhile.Thankstoallthemembersofthe

publishingteam.JackieCarter,yourgentlehandandguidancewere

whatthisbookneeded,andIhopeyouenjoyedourconversationsas

muchasIdid.Thankstothosewholaboredinmyshadowtomake

thisbookthebestitcouldbe.Specifically,Iwanttothanktheteam

thatlaboredsohardtomakethisbooklookgoodandcorrectallofmy

badhabits,includingKimWmi pset,thecopyeditor;SethMaislin,the

indexer;StevePeter,the typesetter;andJanetFurlow,theproducer.

Thisbookwouldnotbewhatitiswithoutyou.

Asalways,mistakesthatslippedthroughthisfineteamareallmine.

ForthoseofyouImissed,Ioffermysincerestapologies.Anyoversight

wasnotintentional.

Finally,thankstoallofmyreaders.Ithinkthatrealhard-copybooks

havevalue,andIcanfollowmypassionandwritebecauseyoudo,too.

BruceTate

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Foreword

From the yet to be written “How Proust Can Make You a Better

Programmer”

byJoeArmstrong ,CreatorofErlang

“TheGmaileditorcannotgettypographicquotesright.”

“Disgraceful,”saidMargery,“thesignofanilliterateprogrammeranda

decadentculture.”

“Whatshouldwedoaboutit?”

“Wemustinsistthatthenextprogrammerwehirehasreadallof‘Ala

recherchedutempsperdu.”’

“Allsevenvolumes?”

“Allsevenvolumes.”

“Willitmakethembetteratpunctuationandmakethemgettheirquotes

right?”

“Notnecessarily,butitwillmakethemabetterprogrammer.It’saZen

thing....”

Learningtoprogramislikelearningtoswim.Noamountoftheoryis

asubstitutefordivingintothepoolandflailingaroundinthewater

gaspingforair.Thefirsttimeyousinkunderthewater,youpanic,but

whenyoubobtothesurfaceandgulpinsomeair,youfeelelated.You

thinktoyourself,“Icanswim.”Atleastthat’showIfeltwhenIlearned

toswim.

It’sthesamewithprogramming.Thefirststepsarethemostdifficult,

andyouneedagoodteachertoencourageyoutojumpintothewater.

BruceTateissuchateacher.Thisbookgivesyoutheopportunityto

startwithwhatisthemostdifficultpartoflearningtoprogram,namely,

gettingstarted.

FOREWORD 15

Let’sassumethatyou’veactuallymanagedthedifficulttaskofdown￾loadingandinstallingtheinterpreterorcompilerforthelanguageyou

are interested in. What should youdonext?What will be your first

program?

Bruce neatly answers this question. Justtype in the programs and

programfragmentsinthisbooktoseewhetheryoucanreproducehis

results.Don’tthinkaboutwritingyourownprogramsyet—justtryto

reproducetheexamplesinthebook.Asyougrowinconfidence,you

willbeabletotackleyourownprogrammingprojects.

Thefirststepinacquiringanynewskillisnotbeingabletodoyourown

thingbutbeingabletoreproducewhatotherpeoplehavedonebefore

you.Thisisthequickestwaytomasteringaskill.

Gettingstartedwithprogramminginanewlanguageisnotsomuch

adeepexerciseinunderstandingtheunderlyingprinciplesthatalan￾guage embodies; itis rather a matter of getting the semicolons and

commas inthe rightplacesandunderstanding theweirderrormes￾sagesthatthesystemspitsoutwhenyoumakeanerror.Itisnotuntil

yougetbeyondthemessybusinessofenteringaprogramandgettingit

throughthecompilerthatyoucanevenstarttothinkaboutthemean￾ingofthedifferentlanguageconstructs.

Onceyou’vegottenthroughthemechanicsofenteringandrunningpro￾grams,youcansitbackandrelax.Your subconsciousdoestherest.

Whileyourconsciousbrainisfiguringoutwheretoputthesemicolons,

yoursubconsciousisfiguringoutthedeepmeaningthatliesunder￾neaththesurfacestructures.Thenyou’llwakeuponedaysuddenly

understandingthedeepermeaningofalogicprogramorwhyapartic￾ularlanguagehadaparticularconstruct.

Knowingasmallamountaboutmanylanguagesisausefulskill.Ioften

findthatIneedtounderstandabitofPythonorRubytosolveapar￾ticularproblem.TheprogramsIdownloadfromtheInternetareoften

writteninavarietyoflanguagesandneedalittletweakingbeforeIcan

usethem.

Eachlanguagehasitsownsetofidioms,itsstrengths,anditsweak￾nesses.Bylearningseveraldifferentprogramminglanguages,youwill

beabletoseewhichlanguageisbestsuitedtothekindsofproblems

thatinterestyoumost.

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