网络五子棋五子棋设计与实现-外文翻译

外文资料C+isdesignedtobeanextensibleplatformforrapidlydevelopingprogramanalysistools.SeveralfeaturesofC+facilitatethis:Byconvention,C+writteninlowercaselettersrefersjusttotheprogramthatabstractsdatafromaC+program.CIA+writtenincapitallettersreferstothesystemmadeofthatabstractorandallofthetoolsthatusethedatabaseitgenerates.Entitiesincludeles,macros,types,functionsandvariables.SeparationofInformationExtractionandPresentation:Theprocessofextractinginformationfromaprogramandtheprocessofpresentingthatinformationshouldbeseparate.ThiseliminatestheneedforeachC+analysistooltoduplicatetheparsingprocessandallowsC+toolstosharetheinformationandpresentitindifferentways.AsimilardoctrinewasdevelopedintheInterlispproject.Unfortunately,manyCandC+toolstodaystillviolatethisbasicprinciple.ThesebasicdesignprinciplesgivetoolsbasedonC+anadvantageovermanytraditionaldevelopmenttools,whichusuallymergetheinformationextractionandpresentationprocessesinasingletoolanddonotsharetheinformationwithothertools.Thefirstprogramminglanguageswereverydependentontheunderlyingmachinearchitecture.Writingprogramsatthislevelofdetailisverycumbersome.Justashardwareengineerslearnedhowtobuildcomputersystemsoutofothercomponents,languagedesignersalsorealizedthatprogramscouldbewrittenatamuchhigherlevel,therebyshieldingtheprogrammerfromthedetailsoftheunderlyingmachine.SoftwareDesignthroughParadigmsWhendesigningsmallcomputerprogramsorlargesoftwaresystems,weoftenhaveamentalmodeloftheproblemwearetryingtosolve.Howdowedeviseamentalmodelofasoftwaresystem?Programmingparadigmsoffermanydifferentwaysofdesigningandthinkingaboutsoftwaresystems.Aparadigmcanbethoughtofasamentalmodelorasaframeworkfordesigninganddescribingasoftwaresystemsstructure.Themodelhelpsusthinkaboutandformulatesolutions.Wecanusethementalmodelofaparadigmindependentlyfromtheprogramminglanguagechosenforimplementation.However,whenthechosenlanguageprovidesconstructsandmechanismsthataresimilartothosethatarefoundintheparadigm,theimplementationwillbemorestraightforward.Usually,thereareseverallanguagesthatbelongtoaparadigm.Forthisreason,aprogrammingparadigmisalsoconsideredaclassoflanguages.Alanguagedoesnothavetofitintojustoneparadigm.Moreoften,languagesprovidefeaturesorcharacteristicsfromseveralparadigms.Hybridlanguages,suchasC+,combinecharacteristicsfromtwoormoreparadigms.C+includescharacteristicsfromtheimperativeandproceduralparadigms-justlikeitspredecessorlanguage,C-andtheobject-orientedparadigm.Theimperativeparadigmischaracterizedbyanabstractmodelofacomputerwithalargememorystore.ThisistheclassicvonNeumannmodelofcomputerarchitecture.Computations,whichconsistofasequenceofcommands,arestoredasencodingwithinthestore.Commandsenablethemachinetofindsolutionsusingassignmenttomodifythestore,variablestoreadthestore,arithmeticandlogictoevaluateexpressions,andconditionalbranchingtocontroltheflowofexecution.Theproceduralparadigmincludestheimperativeparadigm,butextendsitwithanabstractionmechanismforgeneralizingcommandsandexpressionsintoprocedures.Parameters,whichareessentiallyaliasesforaportionofthestore,werealsointroducedbythisparadigm.Otherfeaturesincludeiteration,recursion,andselection.Mostmainstreamsprogrammingtodayisdoneinaprocedurallanguage.Theproceduralparadigmwasthefirstparadigmtointroducethenotionofabstractionintoprogramdesign.Thepurposeofabstractioninprogrammingistoseparatebehaviorfromimplementation.Proceduresareaformofabstraction.Theprocedureperformssometaskorfunction.Otherpartsoftheprogramcalltheprocedure,knowingthatitwillperformthetaskcorrectlyandefficiently,butwithoutknowingexactlyhowtheprocedureisimplemented.DATAABSTRACTIONisconcernedwithseparatingthebehaviorofadataobjectfromitsrepresentationorimplementation.Forexample,astackcontainstheoperationsPush,Pop,andIsEmpty.Astackobjectprovidesuserswiththeseoperations,butdoesnotrevealhowthestackisactuallyimplemented.Thestackcouldbeimplementedusinganarrayoralist.Usersofthestackobjectdonotcarehowthestackisimplemented,onlythatitperformstheaboveoperationscorrectlyandefficiently.Becausetheunderlyingimplementationofthedataobjectishiddenfromitsusers,theimplementationcaneasilybechangedwithoutaffectingtheprogramsthatuseit.Whenwedesignalgorithms,weoftenneedaparticulardatatypetouseinordertocarryoutthealgorithmsoperations.Thedesignofanalgorithmiseasierifwesimplyspecifythedatatypesofthevariables,withoutworryingabouthowtheactualdatatypeisimplemented.Wedescribethedatatypebyitspropertiesandoperationsandassumethatwhateverimplementationischosen,theoperationswillworkcorrectlyandefficiently.TypesdefinedinthiswayarecalledABSTRACTDATATYPES(ADTs).Theuseofabstractdatatypesmakesthedesignofthealgorithmmoregeneral,andallowsustoconcentrateonthealgorithmathandwithoutgettingboggeddowninimplementationdetails.Afterthealgorithmshavebeendesigned,theactualdatatypeswillneedtobeimplemented,alongwiththealgorithms.Recently,procedurallanguageshavebeenextendedtosupportthedefinitionofnewdatatypesandprovidefacilitiesfordataabstraction.Theobject-orientedparadigmretainsmuchofthecharacteristicsoftheproceduralparadigm,sinceproceduresarestilltheprimaryformforcomposingcomputations.However,ratherthanoperateonabstractvalues,programsintheobject-orientedparadigmoperateonobjects.Anobjectisverysimilartoanabstractdatatypeandcontainsdataaswellasprocedures.Therearethreeprimarycharacteristicsoftheobject-orientedparadigm.Wehavealreadydescribedthefirst,ENCAPSULATION,themechanismforenforcingdataabstraction.ThesecondcharacteristicisINHERITANCE.Inheritanceallowsnewobjectstobecreatedfromexisting,moregeneralones.Thenewobjectbecomesaspecializedversionofthegeneralobject.Newobjectsneedonlyprovidethemethodsordatathatdifferbecauseofthespecialization.Whenanobjectiscreated(orderived)fromanotherobject,itissaidtoinheritthemethodsanddataoftheparentobject,andincludesanynewrepresentationsandneworrevisedmethodsaddedtoit.Thethirdandfinalcharacteristicofobject-orientedprogrammingisPOLYMORPHISM.Polymorphismallowsmanydifferenttypesofobjectstoperformthesameoperationbyrespondingtothesamemessage.Forexample,wemayhaveacollectionofobjectswhichcanallperformasortoperation.However,wedonotknowwhattypesofobjectswillbecreateduntilrun-time.Object-orientedlanguagescontainmechanismsforensuringthateachsortmessageissenttotherightobject.Constructinganobject-orientedprograminvolvesdeterminingtheobjectsthatareneededtosolvetheproblem.Theobjectsarethenusedtoconstructcomputationsthatdefinethebehaviorofthesoftwaresystem.Messagepassingisthefundamentalinteractionmechanismamongobjects.Messages(fromotherobjectsorprograms)aresenttoobjectstoinformthemtoperformoneoftheiroperations.Objectsareresponsibleformaintainingthestateoftheirdata.Onlytheobjectmaymodifyitsinternaldata.Objectsmaythemselvesbeimplementedviaothersub-objects.Implementinganobjectinvolvesarecursiveprocessofbreakingitintosub-objectsuntilatsomeleveltheobjectsandmethodsdefinedonthemareprimitives.Atthispoint,themethodsanddataconsistofelementsthatcanbeimplementedusingthebasicconstructsprovidedbytheprogramminglanguage.Oneofthemostimportantaspectsoftheobject-orientedparadigmishowitchangesourwayofthinkingaboutsoftwaresystems.Systemsarethoughtofasconsistingofindividualentitiesthatareresponsibleforcarryingouttheirownoperations.Eachobjectisconceivedandimplementedasself-contained.Suchamodelfacilitatessoftwaredesign(andlaterimplementation)becauseobjectsoftenmodelconceptualreal-worldentities.Designingsystemsusingtheobject-orientedparadigmresultsinsoftwaresystemsthatbehaveandappearmoreliketheirreal-lifecounterparts.TheObject-OrientedCharacteristicsofC+C+extendsCwithafacilityfordefiningnewdatatypes.AclassislikeaCstruct,butcontainsdataaswellasmethods.Inaddition,C+providesdifferentlevelsofaccesstothemembersofaclassinordertocontrolhowthemembersofaclasscanbemanipulatedfromoutsidetheclass.Recallthattheimportanceofdataabstractionistohidetheimplementationdetailsofadataobjectfromtheuser.TheuseronlyaccessestheobjectthroughitsPUBLICINTERFACE.AC+classconsistsofapublicandprivatepart.Thepublicpartprovidestheinterfacetotheusersoftheclass,whiletheprivatepartcanonlybeusedbythefunctionsthatmakeuptheclass.C+provideskeywordstoindicatewhichmembersofaclassarehiddenandwhicharepartofitspublicinterface.Themembersofthehiddenimplementationaremarkedinsectionsbeginningwiththekeywordprivate.Thepublicinterfacepartoftheclassfollowsthekeywordpublic.Bydefault,thedeclarationswithinaclassareprivate,meaningthatonlythememberfunctions(andfriends)oftheclasshaveaccesstothem.Aclassdefinitiondoesnotallocateanymemory.Memoryisallocatedwhenanarrayobjectiscreatedthroughavariabledeclaration.Constructorsanddestructorsprovidetheinitializationandcleanupofanobject.Whenanobjectisdeclared,theconstructoriscalledtoinitializethememoryusedbytheobject.Thedestructorperformsanyclean-upfortheobjectwhentheobjectgoesoutofscopeandisdestroyed.Notethatwedidntreallyhidetheimplementationdetailsfromtheuser.C+doesnotprovideawaytocompletelyexcludeallofthedetailsoftheunderlyingimplementation,sincetheprivatepartoftheclassmustbeincludedwiththeclassdefinitionitisusefultorelaxtheaccesstovariableswithinaclass,particularlyunderinheritance.Oftenderivedclassesneedeasyaccesstotheprivatemembersoftheirparentclasses.C+definesthekeywordprotectedforthispurpose.Protectedmemberscanbeaccessedbythememberfunctionsofaclassaswellasbymemberfunctionsofderivedclasses.However,likeprivatemembers,protectedmemberscannotbeaccessedbyuserprograms.Object-orientationhasbecomeabuzzwordwithmanymeanings.Itisadesignmethodology,aparadigm(awayofthinkingaboutproblemsandfindingsolutions),andaformofprogramming.Asadesignmethodology,wecanuseobject-orientedtechniquestodesignsoftwaresystems.Butitismorethanadesignmethodology,itisawholenewwayofthinkingaboutproblems.Object-orienteddesignallowsustothinkabouttheactualreal-worldentitiesoftheproblemweareattemptingtoprovideasolutionfor.Beginningthedesignwithconceptsfromthereal-worldproblemdomainallowsthesameconceptstobecarriedovertoimplementation,makingthedesignandimplementationcyclemoreseamless.Onceadesignhasbeenconceived,aprogramminglanguagecanbechosenforimplementation.Byfactoringouttheinheritancerelationshipsfromtheobjecthierarchiesdiscoveredduringdesign,onecanevenimplementthesysteminatraditional,non-object-orientedlanguage.However,usinganobject-orientedlanguage,suchasC+,makesiteasiertorealizethedesignintoanimplementationbecausetheinherentrelationshipsamongobjectscanbedirectlysupportedinthelanguage.LanguagessuchasC+areconsideredhybridlanguagesbecausetheyaremulti-paradigmlanguages.C+isanobject-orientedextensionofCandcanbeusedasaprocedurallanguageorasanobject-orientedlanguage.Inthisissue,wecontinueourtouroftheobject-orientedfeaturesofC+.Oneofthemajorstrengthsofanyobject-orientedprogramminglanguageistheabilitytobuildotherclassesfromexistingclasses,therebyreusingcode.Inheritanceallowsexistingtypestobeextendedtoanassociatedcollectionofsub-types.Recallthatoneofthekeyactionsofobject-orienteddesignistoidentifyreal-worldentitiesandtherelationshipsamongthem.Whenasoftwaresystemisdesigned,avarietyofobjectsarise,whichmayberelatedinonewayoranother.Someclassesmaynotberelatedatall.Manytimesitmakessensetoorganizetheobjectclassesintoaninheritancehierarchy.Organizingasetofclassesintoaclasshierarchyrequiresthatweunderstandtherelationshipsamongtheclassesindetail.Notallclassrelationshipsdictatethatinheritancebeused.C+providesthreeformsofinheritance:public,private,andprotected.Thesedifferentformsareusedfordifferentrelation-shipsbetweenobjects.Toillustratethesedifferenttypesofinheritance,letslookatseveraldifferentclassrelationships.Itisbesttousecompositionwherepossible.Incaseswhereyoumustoverridefunctionsinabaseclassthenbyallmeansuseinheritance.Onlyusepublicinheritanceifyourderivedclassisindeedaspecializationofthebaseclass,otherwise,privateinheritanceshouldbeused.Needlesslyusinginheritancemakesyoursystemhardertounderstand.Insummary,aclassspecifiestwointerfaces:onetotheusersoftheclass(thepublicinterface)andanothertoimplementersofderivedclasses(theunionofpublicandprotectedparts).Inheritanceworksalmostidentically.Whentheinheritanceispublic,thepublicinterfaceofthebaseclassbecomespartofthepublicinterfacetousersofthederivedclass.Whentheinheritanceisprotected,thepublicandprotectedpartsofthebaseclassareaccessibletothememberfunctions(theimplementation)ofthederivedclasses,butnottogeneralusersofthederivedclasses.Finally,wheninheritanceisprivate,thepublicandprotectedpartsofthebaseclassareonlyaccessibletotheimplementeroftheclass,butnottousersorderivedclasses.Polymorphismisthelastofthethreefundamentalprimitivesofobject-orientedprogrammingandthemostimportant.Togetherwithinheritance,polymorphismbringsthemostpower,intermsofrun-timeflexibility,toobject-orientedprogramming.Polymorphism,whichmeansmanyforms,providesagenericsoftwareinterfacesothatacollectionofdifferenttypesofobjectsmaybemanipulateduniformly.C+providesthreedifferenttypesofpolymorphism:virtualfunctions,functionnameoverloading,andoperatoroverloading.Thevirtualfunctionmechanismcanonlybeinvokedthroughtheuseofabaseclassreferenceorpointer.Recallthatabaseclasspointercanpointtoanobjectofthebasetypeoranobjectofanytypethatisderivedfromthebaseclass.Virtualfunctionsarealsousedtoimplementthelogicgatehierarchy.Theclassgateisanabstractbaseclassattherootoftheinheritancehierarchy.Aclassisconsideredabstractwhensomeofitsvirtualmemberfunctionsdonothaveanimplementation.Thesefunctionsareassignedtobezerointheclassdefinition.Derivedclassesmustprovideimplementationsforthem.AnotherformofpolymorphismfoundinC+isfunctionoverloading.Afunctionissaidtobeoverloadedwhenitisdeclaredmorethanonceinaprogram.Overloadingallowsasetoffunctionsthatperformasimilaroperationtobecollectedunderthesamename.Whenthereareseveraldeclarationsofthesamefunction,thecompilerdetermineswhichfunctionshouldbecalledbyexaminingthereturntypeandargumentsignatureofthefunctioncall.Whenwedefinenewdatatypes,itisoftenusefultodefinestandardoperationsthatarefoundinsimilartypes.Forexample,acomplextypealsohasadditionandsubtractiondefinedforit.Wecanuseoperatoroverloadingsothattheaddition(+)andsubtraction(-)operatorsworkforcomplexobjectsjustastheydoforintsandfloats.OperatorsaredefinedinmuchthesamewasasnormalC+functionsandcanbemembersornon-membersofaclass.Operatorstakeoneortwoargumentsandarecalledunaryandbinaryoperatorsaccordingly.InC+,amemberoperatorfunctionisdefinedlikeanordinarymemberfunction,butthenameisprefixedwiththekeywordoperator.中文翻译C+被设计成一个用于快速开发程序分析工具的可扩展平台。C+有以下几个特点：按照惯例，C+中小写字母是指书写的程序，只是从C+程序的摘要数据。C+中的大写字母书写，是指该摘要作者和使用的工具生成所有数据库中取得的。宏包括单位类型、函数和变量。这些基本的设计原理为基于C+中编程提供基础，在许多传统的开发工具中，通常的信息提取和合并是在一个单一的工具演示过程中的，不能共享与其他工具的信息优势。一种语言不仅要符合一种范例，而且能够使用多种范例提供的特性和特征。混合语言，如C+，综合了两到三种范例。C+包括了命令和程序范例的特性，例如，其前身C,和面向对象范例。当我们设计一个算法时，需要一个特定的数据类型执行算法的操作。如果可以定义变量的数据类型，而不影响到实际数据类型的运行，就可以很容易的制订出算法。通过定义数据的用法和操作，假定可以选择任何一种运行，这种定义就叫做抽象数据类型。抽象数据类型的使用使得算法的设计得到更大的推广，使得我们在算法设计时，注重了算法的全面，而不会拘泥于运行的细节。当算法设计完成时，实际的数据类型被执行。近来，程序语言扩展到支持新的数据类型的定义和提供便利给数据抽象。面向对象的范例：它仍然保留了许多程序范例的特征，过程仍然是计算的主要形式。但是，程序不仅仅是抽象值的运算，在面向对象范例种还有对对象的运算。对象同抽象数据类型很相似，联系着数据和运算。面向对象范例具有三种主要特性，第一种，压缩，其机制是为了实施数据抽象。第二种，继承。继承允许从已存在的对象中创建新的对象。这个新创建的对象是原对象的具体说明。新对象的不同在于只需要提供方法或数据。当一个对象从另一个对象中被创建或取得时，就说新对象继承了它父对象的方法和数据，并增加了一些新的描述和说明。面向对象的第三种特性是多态。多态可以使不同类型的的对象对相同的信息执行相同的操作。例如，我们有一部分对象它们可以执行一类操作，但是只有在运行时我们才知道对象的类型。面向对象语言包含的机制确保了每一类信息传递给正确的对象。构建一个面向对象的程序需要决定解决问题所需的对象。这些对象被用来构建计算，定义软件系统的操作运行。信息的传递是对象间最基本的相互作用机制。信息（从其他的对象或程序）传递给对象，以便通知对象运行下一个操作。对象需要负责维护它所相关的数据的状态。只有对象本身才可以改变它内部的数据值。对象本身可以完全的调用它的子对象。一个对象的执行是一个循环