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1、OnUnderstandingDataAbstraction,RevisitedWilliamR.CookUniversityofTexasatAustinwcook@cs.utexas.eduAbstractSowhatisthepointofaskingthisquestion?Everyoneknowstheanswer.It’sinthetextbooks.TheanswermaybeIn1985LucaCardelliandPeterWegner,myadvisor,pub-alittlefuzzy,butnobodyfeelst
2、hatit’sabigissue.IfIdidn’tlishedanACMComputingSurveyspapercalled“Onun-presstheissue,everyonewouldnodandtheconversationderstandingtypes,dataabstraction,andpolymorphism”.wouldmoveontomoreimportanttopics.ButIdopresstheTheirworkkickedoffafloodofresearchonsemanticsandissue.Idon’
3、tsayit,buttheycantellIhaveanagenda.typetheoryforobject-orientedprogramming,whichcontin-Mypointisthatthetextbooksmentionedaboveareuestothisday.Despite25yearsofresearch,thereisstillwrong!Objectsandabstractdatatypesarenotthesamewidespreadconfusionaboutthetwoformsofdataabstrac
4、-thing,andneitheroneisavariationoftheother.Theyaretion,abstractdatatypesandobjects.Thisessayattemptstofundamentallydifferentandinmanywayscomplementary,explainthedifferencesandalsowhythedifferencesmatter.inthatthestrengthsofonearetheweaknessesoftheother.CategoriesandSubject
5、DescriptorsD.3.3[ProgrammingTheissuesareobscuredbythefactthatmostmodernpro-Languages]:LanguageConstructsandFeatures—Abstractgramminglanguagessupportbothobjectsandabstractdatadatatypes;D.3.3[ProgrammingLanguages]:Languagetypes,oftenblendingthemtogetherintoonesyntacticform.C
6、onstructsandFeatures—ClassesandobjectsButsyntacticblendingdoesnoterasefundamentalsemanticdifferenceswhichaffectflexibility,extensibility,safetyandGeneralTermsLanguagesperformanceofprograms.Therefore,tousemodernpro-Keywordsobject,class,abstractdatatype,ADTgramminglanguagesef
7、fectively,oneshouldunderstandthefundamentaldifferencebetweenobjectsandabstractdata1.Introductiontypes.WhileobjectsandADTsarefundamentallydifferent,Whatistherelationshipbetweenobjectsandabstractdatatheyarebothformsofdataabstraction.Thegeneralcon-types(ADTs)?Ihaveaskedthisqu
8、estiontomanygroupsofceptofdataabstractionreferstoanymechanismforhidingcomputerscientistso
