程序設(shè)計(jì)語言原理-復(fù)習(xí)課件

ConceptsofProgrammingLanguages程序設(shè)計(jì)語言原理-復(fù)習(xí)ReviewChapter1:

PreliminariesMotivationProgrammingDomainsLanguageEvaluationCriteriaInfluencesonLanguageDesignLanguageCategoriesLanguageDesignTrade-OffsImplementationMethodsProgrammingEnvironments

程序設(shè)計(jì)語言原理-復(fù)習(xí)1.3LanguageEvaluationCriteriaReadabilityThemostimportantcriteriumFactors:OverallsimplicityToomanyfeaturesisbadMultiplicityoffeaturesisbadOperatoroverloadingOrthogonalityMakesthelanguageeasytolearnandreadMeaningiscontextindependentArelativelysmallsetofprimitiveconstructscanbecombinedinarelativelysmallnumberofwaysEverypossiblecombinationislegalLackoforthogonalityleadstoexceptionstorules正交性：指只用該語言的一組相對(duì)少量的基本結(jié)構(gòu)，經(jīng)過相對(duì)少的結(jié)合步驟，就可構(gòu)成該語言的控制結(jié)構(gòu)和數(shù)據(jù)結(jié)構(gòu)。而且，它的基本結(jié)構(gòu)的任何組合都是合法和有意義的。count=count+1count+=1count++++count程序設(shè)計(jì)語言原理-復(fù)習(xí)1.3LanguageEvaluationCriteriaReadabilityWritabilityReliabilityCost程序設(shè)計(jì)語言原理-復(fù)習(xí)1.5LanguageCategoriesImperativeCentralfeaturesarevariables,assignmentstatements,anditerationC,PascalFunctionalMainmeansofmakingcomputationsisbyapplyingfunctionstogivenparametersLISP,Scheme程序設(shè)計(jì)語言原理-復(fù)習(xí)1.5LanguageCategoriesLogicRule-basedRulesarespecifiedinnospecialorderPrologObject-orientedEncapsulatedataobjectswithprocessingInheritanceanddynamictypebindingGrewoutofimperativelanguagesC++,Java程序設(shè)計(jì)語言原理-復(fù)習(xí)1.7ImplementationMethodsCompilationTranslatehigh-levelprogramtomachinecodeCCOBOLAdaSlowtranslationFastexecutionBottleneck:thespeedoftheconnectionbetweenacomputer’smemoryanditsprocessor.TheVonNeumannbottleneckhasbeenoneofthePrimarymotivationsfortheresearchanddevelopmentofparallelcomputers.程序設(shè)計(jì)語言原理-復(fù)習(xí)Chapter2:EvolutionofthemajorprogramminglanguagesZuse’sPlankalkulMinimalHardwareProgramming:PseudocodesTheIBM704andFORTRANFunctionalProgramming:LISPTheFirstStepTowardSophistication:ALGOL60ComputerizingBusinessRecords:COBOLTheBeginningsofTimesharing:BASICEverythingforEverybody:PL/IReview程序設(shè)計(jì)語言原理-復(fù)習(xí)9.TwoEarlyDynamicLanguages:APLandSNOBOL10.TheBeginningsofDataAbstraction:SIMULA6711.OrthogonalDesign:ALGOL6812.SomeEarlyDescendantsoftheALGOLs13.ProgrammingBasedonLogic:Prolog14.Hisotry’sLargestDesignEffort:AdaObject-OrientedProgramming:SmalltalkCombiningImperativeandObject-OrientedFeatures:C++Programmingtheworldwideweb:JavaReview程序設(shè)計(jì)語言原理-復(fù)習(xí)Chapter5:Names,Bindings,TypeChecking,andScopesIntroductionNamesVariables(屬性，別名，左值，右值P183)TheConceptofBinding(動(dòng)態(tài)和靜態(tài)綁定、生命周期)TypeCheckingStrongTypingTypeCompatibilityScopeScopeandLifetimeReferencingEnvironmentsNamedConstantsVariableInitializationReview程序設(shè)計(jì)語言原理-復(fù)習(xí)5.2Names(cont.)SpecialwordsAnaidtoreadability;usedtodelimit(界定)orseparatestatementclausesDef:A

keywordisawordthatisspecialonlyincertaincontexts.i.e.inFORTRAN:RealVarName(Realisdatatypefollowedwithaname,thereforeRealisakeyword)

Real=3.4(Realisavariable) Disadvantage:poorreadabilityDef:Areservedwordisaspecialwordthatcannotbeusedasauser-definedname程序設(shè)計(jì)語言原理-復(fù)習(xí)5.3VariablesAvariableisanabstractionofamemorycellVariablescanbecharacterizedasasextuple(六個(gè)部分)ofattributes:(name,address,value,type,lifetime,scope)Name-notallvariableshavethem(anonymous(匿名的))程序設(shè)計(jì)語言原理-復(fù)習(xí)

兩個(gè)變量具有按名等價(jià)的類型當(dāng)且僅當(dāng)它們一起被說明，或者用相同的類型標(biāo)識(shí)符說明，即對(duì)應(yīng)的類型名相同。如:typeTisarray[1..100]ofINTEGER;(Ada)

x,y:array[1..100]ofINTEGER;（P198）z:array[1..100]ofINTEGER;r,w:T;i,j:FLOAT;按名等價(jià)：

r與w,i與jx與y、x與z按名不等價(jià)，z與r按名不等價(jià).按名等價(jià)(Nametypecompatibility)程序設(shè)計(jì)語言原理-復(fù)習(xí)

兩個(gè)變量具有按結(jié)構(gòu)等價(jià)的類型當(dāng)且僅當(dāng)變量的所有分量有相同類型的值集。在上例中，u和v第二個(gè)分量的值集是相同的，所以按結(jié)構(gòu)等價(jià)。

x和u呢？按結(jié)構(gòu)等價(jià)雖然第二個(gè)分量的值均為整數(shù)，但其類型不同，所以不是按結(jié)構(gòu)等價(jià)的。程序設(shè)計(jì)語言原理-復(fù)習(xí)兩個(gè)變量具有按定義等價(jià)的類型當(dāng)且僅當(dāng)兩個(gè)變量有完全相同的類型（包括相同的域名）。除類型名外的其他特征均相同者即視為按定義等價(jià)。如typecomplex=recordre:int;im:intend;Typerational=recordnominator:int;denominator:1..299999end;

按定義等價(jià)(declarationequivalence)程序設(shè)計(jì)語言原理-復(fù)習(xí)programexample;vara,b:integer;……

proceduresubl;varx,y:integer;begin{subl}…..1end;{subl}

proceduresub2;varx:integer;……

proceduresub3;varx:integer;begin{sub3}……2end;{sub3}

begin{sub2}……..3

end;{sub2}begin{example}……4end.{example}Point

Referencing

Environmentxandyofsubl,aandb

ofexample2xofsub3,(xofsub2ishidden),aandbofexample3xofsub2,aandbofexample4aandbofexampleInastatic-scopedlanguage程序設(shè)計(jì)語言原理-復(fù)習(xí)voidsubl(){inta,b;

…….1}/*endofsubl*/voidsub2(){intb,c;

……2

subl();}/*endofsub2*/voidmain(){intc,d;

……3

sub2();}/*endofmain*/

Point

ReferencingEnvironment1aandbofsub1,cofsub2,dofmain,,(cofmainandbofsub2arehidden)2bandcofsub2,dofmain,(cofmainishidden)3canddofmainFunctioncall:Main--->sub2---->sub1Inadynamic-scopedlanguage程序設(shè)計(jì)語言原理-復(fù)習(xí)Chapter6:DataTypes1.Introduction2.PrimitiveDataTypes3.CharacterStringTypes4.User-DefinedOrdinalType:5.ArrayTypes6.RecordTypes7.UnionTypes8.SetTypes

10.PointerTypes(懸掛指針P263)Review程序設(shè)計(jì)語言原理-復(fù)習(xí)Chapter7:ExpressionsandAssignmentStatementsIntroductionArithmeticExpressions(函數(shù)副作用)OverloadedOperators(操作符重載)TypeConversionsRelationalandBooleanExpressionsShort-CircuitEvaluationAssignmentStatementsMixed-modeAssignmentReview程序設(shè)計(jì)語言原理-復(fù)習(xí)6.10PointerTypesPointerProblemsDanglingPointers(懸掛指針):isapointerthatcontainstheaddressofaheap-dynamicvariablethathasbeendeallocated(解除分配).

Danglingpointersaredangerous

thelocationmayhavebeenreallocatedthevalueofthenewheap-dynamicvariablewillbedestroyedstoragemanagertofail

LostHeap-dynamicVariables:isanallocatedheap-dynamicvariablethatisnolongeraccessibletotheuserprogram.Suchvariablesarecalledgarbage(垃圾)程序設(shè)計(jì)語言原理-復(fù)習(xí)OperandEvaluationOrder

Ifneitheroftheoperandsofanoperatorhassideeffects,thenoperandevaluationorderisirrelevant(不相關(guān)的)

Sideeffects

Def:

functional

side

effect,occurswhenthefunctionchangeseitheroneofitsparametersoraglobalvariable

Example

a=10;10+5=15(fromlefttoright)b=a+fun(a);20+5=25(fromrighttoleft)funreturnsthevalueofitsargumentdividedby2andchangesitsparametertohavethevalue207.2ArithmeticExpressions

程序設(shè)計(jì)語言原理-復(fù)習(xí)7.3OverloadedOperatorsArithmeticoperatorsareoftenusedformorethanonepurpose.Multipleuseofanoperatoriscalledoperator

overloading

x=&y

(1)Binaryoperator:AND(2)Unaryoperator:theadrressofthatvariableTwoproblem(1)Detrimental(有害的)toreadability(2)someerrorundetectedbythecompiler.程序設(shè)計(jì)語言原理-復(fù)習(xí)Chapter8:Statement-LevelControlStructuresIntroductionCompoundStatementsSelectionStatementsIterativeStatementsUnconditionalBranchingGuardedCommandsConclusions

Review程序設(shè)計(jì)語言原理-復(fù)習(xí)Chapter9:SubprogramsIntroductionFundamentalsofSubprograms(parameterprofile,prototypeFormalparameters,actualparameter,positionandkeywordP..)3.DesignIssuesforSubprograms4.LocalReferencingEnvironments(localvarialbe,advantage..)5.Parameter-PassingMethods6.OverloadedSubprograms(定義)7.GenericSubprograms8.SeparateandIndependentCompilation9.DesignIssuesforFunctions10.AccessingNonlocalEnvironments(P388)(nonlocalvariable,globalvariable)11.User-DefinedOverloadedOperators12.Coroutines

Review程序設(shè)計(jì)語言原理-復(fù)習(xí)9.1IntroductionTwofundamentalabstractionfacilities(設(shè)施)canbeincludedinaprogramminglanguage:processabstractionanddataabstractionProcessabstractionhasbeenacentralconceptinallprogramminglanguages.Thefirstprogrammablecomputer,in1940,hadthecapability(能力)ofreusingcollectionsofinstructioncardsatseveraldifferentplacesinaprogramwhenthatwasconvenient(方便的)Thisreuseresultsinseveraldifferentkindsofsavings,frommemoryspacetocodingtime.Thisincreasesthereadabilityofaprogram.程序設(shè)計(jì)語言原理-復(fù)習(xí)BasicDefinitions(con.)ForexampleFORTRAN:SUBROUTINEADDER(parameters)

Ada:procedureADDER(parameters)C:voidadder(parameters)Theparameter

profile(參數(shù)輪廓)

ofasubprogramisthenumber,order,andtypesofitsformalparameters(形式參數(shù)).Theprotocol(協(xié)議)

ofasubprogramisitsparameterprofileplus,ifitisafunction,itsreturntype.9.2FundamentalsofSubprograms程序設(shè)計(jì)語言原理-復(fù)習(xí)Parameters

Therearetwowaysthatasubprogramgains(得到)accesstothedata:Throughdirectaccesstononlocal(非局部的)variables

ThroughparameterpassingParameterpassingismoreflexible(靈活的)thandirectaccesstononlocalvariables.Extensive(大量)accesstononlocalscancausereducedreliability(可靠性)Theparametersinthesubprogramheaderarecalledformal

parameters.Theyareboundtostorageonlywhenthesubprogramiscalled.9.2FundamentalsofSubprograms程序設(shè)計(jì)語言原理-復(fù)習(xí)Parameters(Con.)

Subprogramcallstatementsmustincludethenameofthesubprogramandalistofparameterstobeboundtotheformalparametersofthesubprogram(actual

parameters.).positional

parameters:thecorrespondence(對(duì)應(yīng))betweenactualandformalparametersisdonebysimpleposition

keyword

parameters:thenameoftheformalparametertowhichanactualparameteristobeboundisspecifiedwiththeactualparameter.(Ada)9.2FundamentalsofSubprograms程序設(shè)計(jì)語言原理-復(fù)習(xí)Variablesthataredefinedinsidesubprogramsarecalledlocalvariables.(eitherstaticorstackdynamic)Stackdynamiclocalvariablesareboundtostoragewhenthesubprogrambeginsexecutionandunboundfromstoragewhenthatexecutionterminates.Advantagesofstack-dynamiclocalvariables:flexibilitythestorageforlocalvariablescanbeshared.Disadvantagesofstack-dynamiclocalvariables:thereisthecostofthetimerequiredtoallocate,initialize,anddeallocate

accessestostack-dynamiclocalvariablesmustbeindirect(間接)subprogramscannotbehistorysensitive

9.4LocalReferencingEnvironments程序設(shè)計(jì)語言原理-復(fù)習(xí)ImplementationModelsofParameterPassing

Pass-by-ValueThevalueoftheactualparameterisusedtoinitializethecorrespondingformalparameterActsasalocalvariableinthesubprogramPass-by-valueisnormallyimplementedbyactualdatatransfer.Thedisadvantage:AdditionalstoragefortheformalparameterThestorageandthemoveoperationscanbecostlyiftheparameterislargePass-by-valueisimplementedbytransmittinganaccesspathtothevalueoftheactualparameterrequirethatthevaluebeinawrite-protectedcell

9.5Parameter-PassingMethods程序設(shè)計(jì)語言原理-復(fù)習(xí)ImplementationModelsofParameterPassing

Pass-by-ResultPass-by-resultisanimplementationmodelforout-modeparameters.NovalueistransmittedtothesubprogramThecorrespondingformalparameteractsasalocalvariable,justbeforecontrolistransferredbacktothecaller,itsvalueispassedbacktothecaller'sactualparameter

AlsorequirestheextrastorageandthecopyoperationsBeingimplementedbydatatransfer,theproblemisinensuringthattheinitialvalueoftheactualparameterisnotusedinthecalledsubprogram.9.5Parameter-PassingMethods程序設(shè)計(jì)語言原理-復(fù)習(xí)ImplementationModelsofParameterPassing

Pass-by-Result(con.)Oneproblemwiththepass-by-resultmodelisthattherecanbeanactualparametercollisionsub(p1,p1)（調(diào)用語句中）AssumingthetwoformalparametershavedifferentnamesTheorderinwhichtheactualparametersareassigneddeterminestheirvalueBecausetheorderisusuallyimplementationdependent,portability(可移植性)problemscanoccurthataredifficulttodiagnose(診斷)

Anotherproblemistochoosetwodifferenttimestoevaluatetheaddressesoftheactualparameters(atthetimeofthecalloratthetimeofthereturn)9.5Parameter-PassingMethodsForexample:

list[index]Ifindexischangedbythesubprogram,thentheaddressoflist[index]willchangebetweenthecallandthereturn程序設(shè)計(jì)語言原理-復(fù)習(xí)ImplementationModelsofParameterPassing

Pass-by-Value-ResultPass-by-value-resultisanimplementationmodelforinout-modeparametersinwhichactualvaluesaremoved.Acombinationofpass-by-valueandpass-by-result.Pass-by-value-resultissometimescalledpass-by-copybecausetheactualparameteriscopiedtotheformalparameteratsubprogramentryandthencopiedbackatsubprogramtermination.Disadvantagesofrequiringmultiplestorageforparametersandtimeforcopyingvalues.Theproblemsassociatedwiththeorderinwhichactualparametersareassigned.9.5Parameter-PassingMethods程序設(shè)計(jì)語言原理-復(fù)習(xí)COPY機(jī)制：機(jī)制實(shí)參進(jìn)入時(shí)出去時(shí)功能功能傳值方式表達(dá)式X:=實(shí)參

傳結(jié)果方式變量實(shí)參:=x傳值--結(jié)果方式變量X:=實(shí)參實(shí)參:=x傳值方式、傳結(jié)果方式、傳值--結(jié)果方式通稱為傳遞形式參數(shù)的COPY機(jī)制。形參x被指定為被調(diào)用過程的一個(gè)局部變量；進(jìn)入時(shí)將實(shí)參值復(fù)制給x，出去時(shí)將x的值復(fù)制給實(shí)參。X如同一個(gè)局部變量一樣，它的值可以取出和更新，進(jìn)入時(shí)創(chuàng)建出去時(shí)刪除。9.5Parameter-PassingMethods程序設(shè)計(jì)語言原理-復(fù)習(xí)ImplementationModelsofParameterPassing

Pass-by-ReferenceThepass-by-referencemethodtransmitsanaccesspath,justanaddresstothecalledsubprogram.Advantagesisthatthepassingprocessitselfisefficient,intermsofbothtimeandspace.Duplicatespaceisnotrequired,norisanycopying.Disadvantageslikelybeslowerbecauseindirectaddressingifonlyonewaycommunicationtothecalledsubprogramisrequired,Inadvertent(不注意的)anderroneous(錯(cuò)誤的)changesmaybemadeAnotherseriousproblemofpass-by-referenceisthataliasescanbecreated.9.5Parameter-PassingMethods程序設(shè)計(jì)語言原理-復(fù)習(xí)ImplementationModelsofParameterPassing

Pass-by-ReferenceseveralwaysaliasescanbecreatedCollisions(沖突)canoccurbetweenactualparametersvoidfun(int*first,int*second)fun(&total,&total)Collisionsbetweenarrayelementscanalsocausealiasesfun(&list[i],&list[j])ifI==jCollisionsbetweenarray-elementparametersandelementsofarrayspassedasarray-nameparametersfun1(&list[i],&list)9.5Parameter-PassingMethods程序設(shè)計(jì)語言原理-復(fù)習(xí)ImplementationModelsofParameterPassing

Pass-by-Referenceseveralwaysaliasescanbecreated(con.)Collisionsbetweenformalparametersandnonlocalvariables9.5Parameter-PassingMethodsint*global;voidmain(){extern

int*global;……

sub(global);

}voidsub(int*local){externint*global;……}Insidesub,localandglobalarealiases.程序設(shè)計(jì)語言原理-復(fù)習(xí)ImplementationModelsofParameterPassing

Pass-by-NamePass-by-nameisaninout-modeparametertransmissionmethod.Whenparametersarepassedbyname,theactualparameteristextuallysubstitutedforthecorrespondingformalparameterinallitsoccurrencesinthesubprogram.Apass-by-nameformalparameterisboundtoanaccessmethodatthetimeofthesubprogramcall,buttheactualbindingtoavalueoranaddressisdelayeduntiltheformalparameterisassignedorreferenced.9.5Parameter-PassingMethods程序設(shè)計(jì)語言原理-復(fù)習(xí)ImplementationModelsofParameterPassing

Pass-by-Name（con.）

Iftheactualparameterisascalarvariable(標(biāo)量變量),thenpass-by-nameisequivalenttopass-by-reference.Iftheactualparameterisaconstantexpression,thenpass-by-nameisequivalenttopass-by-valueIftheactualparameterisanarrayelement,pass-by-namemaybedifferentfromanyothermethodIftheactualparameterisanexpressionthatcontainsavariable,pass-by-nameisagaindifferentfromanyothermethod9.5Parameter-PassingMethods程序設(shè)計(jì)語言原理-復(fù)習(xí)ImplementationModelsofParameterPassing

Pass-by-Name（con.）9.5Parameter-PassingMethods

beginLIST[1]:=2;LIST[2]:=2;GLOBAL:=1;SUB(LIST[GLOBAL])

end;procedureBIGSUB;integerGLOBAL;integer

arrayLIST[1:2];procedureSUB(PARAM);integerPARAM;beginPARAM:=3;GLOBAL:=GLOBAL+1;PARAM:=5end;List[1]=3;List[2]=5;程序設(shè)計(jì)語言原理-復(fù)習(xí)Def:An

overloaded

subprogramisasubprogramthathasthesamenameasanothersubprograminthesamereferencingenvironment.Everyversionofanoverloadedsubprogrammusthaveaunique(唯一的)protocol;Itmustbedifferentfromtheothersinthenumber,order,ortypesofitsparameters,orinitsreturntypeifitisafunction.C++,Java,andAdaincludepredefinedoverloadedsubprograms.InAda,thereturntypeofanoverloadedfunctionisusedtodisambiguate(消除…的歧義)calls.

9.7OverloadSubprograms程序設(shè)計(jì)語言原理-復(fù)習(xí)Thecapabilityofcompilingpartsofaprogramwithoutcompilingthewholeprogramisessentialtotheconstructionoflargesoftwaresystems.Thepartsofprogramthatcanbecompiledaresometimescalledcompilationunits(編譯單元).Thetermseparatecompilation(分別編譯)

meansthatcompilationunitscanbecompiledatdifferenttimes,buttheircompilationsarenotindependentofeachotherifeitheraccessesorusesanyentitiesoftheother.9.9SeparateandIndependentCompilation程序設(shè)計(jì)語言原理-復(fù)習(xí)Usingwith,theprogrammerspecifiestheexternalunitsthatthecodeinthecompilationmustaccess

withGLOBALS,TEXT_IO;procedureEXAMPLEis

……endEXAMPLE;FORTRAN90alsoallowsseparatecompilationofitssubprogramsandmodules.Withindependent

compilation,programunitscanbecompiledwithoutinformationaboutanyotherprogramunits.9.9SeparateandIndependentCompilation程序設(shè)計(jì)語言原理-復(fù)習(xí)Def:Thenonlocal

variablesofasubprogramarethosethatarevisiblewithinthesubprogrambutarenotlocallydeclared.Def:

Global

variablesarethosethatarevisibleinallprogramunits.Theprimaryproblemasthemeansofnonlocalvariablesharingstaticscoping

Agooddealofprogramstructuremaybedictated(指定)bytheaccessibilityofsubprogramsandnonlocalvariablestoothersubprograms,ratherthanbywell-engineeredproblemsolutionsmoreaccesstononlocalsisprovidedthanisnecessary(P204)9.11AccessingNonlocalEnvironments程序設(shè)計(jì)語言原理-復(fù)習(xí)Chapter10:ImplementingSubprogramsTheGeneralSemanticsofCallsandReturns(子程序的聯(lián)接，call,returnP400)ImplementingFORTRAN77Subprograms(activationrecordinstance,靜態(tài)鏈，動(dòng)態(tài)鏈)ImplementingSubprogramsinALGOL-likeLanguagesBlocksImplementingDynamicScopingReview程序設(shè)計(jì)語言原理-復(fù)習(xí)10.1TheGeneralSemanticsofCallsandReturns

Asubprogramcallmustincludethemechanism

-Iflocalvariablesarenotstatic,itmustcausestoragetobeallocatedforthelocalsdeclaredinthecalledsubprogramandbindthosevariablestothatstorage-Itmustsavetheexecutionstatusofthecallingprogramunit-Itmusttransfercontroltothecodeofthesubprogramandreturntotheproperplacewhenthesubprogramexecutioniscompleted.-Thecallmustcausesomemechanismtobecreatedtoprovideaccesstononlocalvariablesthatarevisibletothecalledsubprogram.

程序設(shè)計(jì)語言原理-復(fù)習(xí)10.1TheGeneralSemanticsofCalls

andReturns

AsubprogramReturnmustincludethemechanismIfthesubprogramhasparametersthatareoutmodeandareimplementedbycopyFirst,movelocalvaluesoftheassociatedformalparameterstotheactualparametersNext,ItmustdeallocatethestorageusedforlocalvariablesandrestoretheexecutionstatusofthecallingprogramunitThen,returnthemechanismusedfornonlocalreferencestotheconfigurationithadbeforethecallFinally,

controlmustbereturnedtothecallingprogramunit程序設(shè)計(jì)語言原理-復(fù)習(xí)10.2ImplementingFORTRAN77

SubprogramsActivationrecord

instance（活動(dòng)記錄實(shí)例）

isaconcrete(具體的)exampleofanActivationRecord

程序設(shè)計(jì)語言原理-復(fù)習(xí)10.2ImplementingFORTRAN77

SubprogramsCommonstorage程序設(shè)計(jì)語言原理-復(fù)習(xí)Thereturnaddressoftenconsistsofapointertothecodesegmentofthecallerandanoffsetaddressinthatcodesegmentoftheinstructionfollowingthecall(調(diào)用語句之后那條指令的偏移地址)Thestatic

link(sometimescalledastatic

scopepointer)

pointstothebottomoftheactivationrecordinstanceofanactivationofthestaticparentThedynamic

linkisapointertothetopoftheactivationrecordinstanceofthecaller10.3ImplementingSubprogramsin

ALGOL-likeLanguages

程序設(shè)計(jì)語言原理-復(fù)習(xí)Considerthefollowingprocedure

proceduresub(vartotal

real；part：integer)；varlist：

array[1..5]ofinteger；sum：real；

begin....end；

TheactivationrecordforsubisshowninFigure10.4.10.3ImplementingSubprogramsinALGOL-likeLanguages

程序設(shè)計(jì)語言原理-復(fù)習(xí)10.3ImplementingSubprogramsin

ALGOL-likeLanguages程序設(shè)計(jì)語言原理-復(fù)習(xí)10.3ImplementingSubprogramsin

ALGOL-likeLanguagesintfactorial(intn){1if(n<=1)return1；elsereturn(n*factorial(n–1))；2}voidmain(){intvalue；

value=factorial(3)；3}Recursion程序設(shè)計(jì)語言原理-復(fù)習(xí)10.3Implementing

Subprograms

in

ALGOL-like

Languages程序設(shè)計(jì)語言原理-復(fù)習(xí)程序設(shè)計(jì)語言原理-復(fù)習(xí)程序設(shè)計(jì)語言原理-復(fù)習(xí)10.3ImplementingSubprogramsin

ALGOL-likeLanguages(staticchains)Def：A

static

chainisachainofstaticlinksthatconnectcertainactivationrecordinstancesinthestack.Def:staticdepthbeanintegerassociatedwithastaticscopethatindicates(指出)howdeeplyitisnestedintheoutermost(最外層)scope.Becausethenestingofscopesisknownatcompiletime,thecompilercandeterminenotonlythatareferenceisnonlocalbutalsothelengthofthestaticchainneededtoreachtheactivationrecordinstancethatcontainsthenonlocalobject.程序設(shè)計(jì)語言原理-復(fù)習(xí)10.3ImplementingSubprogramsinALGOL-likeLanguages(staticchains)ThelengthofthestaticchainneededtoreachthecorrectactivationrecordinstanceforanonlocalreferencetoavariableXisexactlythedifference(差值)betweenthestatic_depthoftheprocedurecontainingthereferencetoxandthestatic_depthoftheprocedurecontainingthedeclarationforx.Thisdifferenceiscalledthenesting_depth（嵌套深度）,

or

chain_offset（鏈偏移）,

ofthereference.Itisrepresentedbyanorderedpairofintegers(chain_offset,local_offset)程序設(shè)計(jì)語言原理-復(fù)習(xí)InprocedureSUB1,ReferencetothevariableAatpoints1:(0,3)(local)Atpoints2:(2,3)(twolevelsaway)(BIGSUB)Atpoints3:(1,3)(onelevelaway)(BIGSUB)MAIN_2----------------0

BIGSUB---------------1

SUB1---------------2

SUB2---------------2

SUB3-----------3

程序設(shè)計(jì)語言原理-復(fù)習(xí)ComparethestaticchaininganddisplaymethodsThecostofaccessinglocalsisthesameforthetwomethodsReferencestononlocalsthatareonlyonestaticlevelawaytakethesametimeforbothmethods,butiftheyaremorethanonestaticlevelaway,theywillbefasterwithadisplaybecausenochainmustbefollowed.

10.3

ImplementingSubprogramsinALGOL-likeLanguages(display)程序設(shè)計(jì)語言原理-復(fù)習(xí)Thereareatleasttwodistinct(截然不同的)waysinwhichnonlocalreferencesinadynamic-scopedlanguagecanbeimplemented:deepaccess(深訪問)andshallowaccess（淺訪問）.Whenaprograminalanguagethatusesdynamicscopingreferstoanonlocalvariable,thereferencecanberesolvedbysearchingthroughthedeclarationsintheothersubprogramsthatarecurrentlyactive,beginningwiththeonemostrecentlyactivated.10.5ImplementingDynamicScoping程序設(shè)計(jì)語言原理-復(fù)習(xí)Chapter11:AbstractDataTypeTheConceptofAbstraction(Abstractkinds)2.Encapsulation(encapsulation,)3.IntroductiontoDataAbstraction(abstractdatatype)4.DesignIssues6.ParameterizedAbstractDataTypesReview程序設(shè)計(jì)語言原理-復(fù)習(xí)11.1TheConceptofAbstractionAnabstractionisavieworrepresentationofanentitythatincludesonlytheattributesofsignificanceinaparticularcontext.Abstractionisaweapon(武器)againstthecomplexity(復(fù)雜性)ofprogramming;itspurposeistosimplifytheprogrammingprocess.Thetwofundamentalkindsofabstractionincontemporary(當(dāng)代的)programminglanguagesareprocessabstractionanddataabstraction.程序設(shè)計(jì)語言原理-復(fù)習(xí)11.2EncapsulationDef:AnencapsulationisagroupingofsubprogramsandthedatatheymanipulateWhenthesizeofaprogramreachesbeyondafewthousandlines,twopracticalproblemsappear:modularizationproblemrecompilationproblemAnencapsulationsolvesbothofthepracticalproblemsdescribedabove.程序設(shè)計(jì)語言原理-復(fù)習(xí)11.3IntroductiontoDataAbstractionDef:Anabstractdatatype(anencapsulation),includesonlythedatarepresentationofonespecificdatatypeandthesubprogramsthatprovidetheoperationsforthattype.Object:AninstanceofanabstractdatatypemotivationfordataabstractionAweaponagainstcomplexityAmeansofmakinglargeand/orcomplicatedprogramsmoremanageable程序設(shè)計(jì)語言原理-復(fù)習(xí)Chapter12:SupportforObject-orientedPrograms1.Introduction2.Object-OrientedProgramming3.DesignIssuesforObject-OrientedLanguages9.SupportforObject-OrientedProgramminginC++10.SupportforObject-OrientedProgram