抽象过程-软件外文翻译

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1、TheprogressofAbstractionAllprogramminglanguagesprovideabstractions.Itcanbearguedthatthecomplexityoftheproblemsyou’reabletosolveisdirectlyrelatedtothekindandqualityofabstraction.By“kind”Imean,“Whatisitthatyouareabstracting?”Assemblylanguageisasmallabstractionoftheunderlyin

2、gmachine.Manyso-called“imperative”languagesthatfollowed(suchasFortran,BASIC,andC)wereabstractionsofassemblylanguage.Theselanguagesarebigimprovementsoverassemblylanguage,buttheirprimaryabstractionstillrequiresyoutothinkintermsofthestructureofthecomputerratherthanthestructu

3、reoftheproblemyouaretryingtosolve.Theprogrammermustestablishtheassociationbetweenthemachinemodel(inthe“solutionspace,”whichistheplacewhereyou’remodelingthatproblem,suchasacomputer)andthemodeloftheproblemthatisactuallybeingsolved(inthe“problemspace,”whichistheplacewherethe

4、problemexists).Theeffortrequiredtoperformthismapping,andthefactthatitisextrinsictotheprogramminglanguage,producesprogramsthataredifficulttowriteandexpensivetomaintain,andasasideeffectcreatedtheentire“programmingmethods”industry.Thealternativetomodelingthemachineistomodelt

5、heproblemyou’retryingtosolve.EarlylanguagessuchasLISPandAPLchoseparticularviewsoftheworld(“Allproblemsareultimatelylists”or“Allproblemsarealgorithmic,”respectively).PROLOGcastsallproblemsintochainsofdecisions.Languageshavebeencreatedforconstraint-basedprogrammingandforpro

6、grammingexclusivelybymanipulatinggraphicalsymbols.(Thelatterprovedtobetoorestrictive.)Eachoftheseapproachesisagoodsolutiontotheparticularclassofproblemthey’redesignedtosolve,butwhenyoustepoutsideofthatdomaintheybecomeawkward.Theobject-orientedapproachgoesastepfurtherbypro

7、vidingtoolsfortheprogrammertorepresentelementsintheproblemspace.Thisrepresentationisgeneralenoughthattheprogrammerisnotconstrainedtoanyparticulartypeofproblem.Werefertotheelementsintheproblemspaceandtheirrepresentationsinthesolutionspaceas“objects.”(Ofcourse,youwillalsone

8、edotherobjectsthatdon’thaveproblem-spaceanalogs.)Theideaisthattheprogramisallowedtoadaptitselfto