面向对象程序设计外文翻译2

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1、附录1.外文文献IntroductionToObjects1、TheprogressofabstractionAllprogramminglanguagesprovideabstractions.Itcanbearguedthatthecomplexityoftheproblemsyou’reabletosolveisdirectlyrelatedtothekindandqualityofabstraction.By“kind”Imean,“Whatisitthatyouareabstracting?”Assemblylanguageisasmallabstractionoftheu

2、nderlyingmachine.Manyso-called“imperative”languagesthatfollowed(suchasFORTRAN,BASIC,andC)wereabstractionsofassemblylanguage.Theselanguagesarebigimprovementsoverassemblylanguage,buttheirprimaryabstractionstillrequiresyoutothinkintermsofthestructureofthecomputerratherthanthestructureoftheproblemy

3、ouaretryingtosolve.Theprogrammermustestablishtheassociationbetweenthemachinemodel(inthe“solutionspace,”whichistheplacewhereyou’remodelingthatproblem,suchasacomputer)andthemodeloftheproblemthatisactuallybeingsolved(inthe“problemspace,”whichistheplacewheretheproblemexists).Theeffortrequiredtoperf

4、ormthismapping,andthefactthatitisextrinsictotheprogramminglanguage,producesprogramsthataredifficulttowriteandexpensivetomaintain,andasasideeffectcreatedtheentire“programmingmethods”industry.Thealternativetomodelingthemachineistomodeltheproblemyou’retryingtosolve.EarlylanguagessuchasLISPandAPLch

5、oseparticularviewsoftheworld(“Allproblemsareultimatelylists”or“Allproblemsarealgorithmic,”respectively).PROLOGcastsallproblemsintochainsofdecisions.Languageshavebeencreatedforconstraint-basedprogrammingandforprogrammingexclusivelybymanipulatinggraphicalsymbols.(Thelatterprovedtobetoorestrictive

6、.)Eachoftheseapproachesisagoodsolutiontotheparticularclassofproblemthey’redesignedtosolve,butwhenyoustepoutsideofthatdomaintheybecomeawkward.Theobject-orientedapproachgoesastepfurtherbyprovidingtoolsfortheprogrammertorepresentelementsintheproblemspace.Thisrepresentationisgeneralenoughthatthepro

7、grammerisnotconstrainedtoanyparticulartypeofproblem.Werefertotheelementsintheproblemspaceandtheirrepresentationsinthesolutionspaceas“objects.”(Youwillalsoneedotherobjectsthatdon’thaveproblem-spaceanalogs.)Theideaisthattheprogramis