“There are only two kinds of programming languages: those...

03-60-440:PrinciplesofProgrammingLanguages

Classifica:onofprogramminglanguages

“Thereareonlytwokindsofprogramminglanguages:thosepeoplealwaysbitchaboutandthosenobodyuses.”--BjarneStroustrup

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Categoriesofprogramminglanguages,wikipedia,20101Arraylanguages

2Aspect-orientedlanguages

3Assemblylanguages

4Authoringlanguages

5Commandlineinterfacelanguages

6Compiledlanguages

7Concurrentlanguages

8Dataflowlanguages

9Data-orientedlanguages

10Data-structuredlanguages

11Declara:velanguages

12Esotericlanguages

13Extensionlanguages

14Fourth-genera:onlanguages

15Func:onallanguages

16Interac:vemodelanguages

17Interpretedlanguages

18Itera:velanguages

19List-basedlanguages–LISPs

20LiWlelanguages

21Logic-basedlanguages

22Machinelanguages

23Macrolanguages

24Metaprogramminglanguages

25Mul:paradigmlanguages

26Numericalanalysis

27Non-English-basedlanguages

28Object-orientedclass-basedlanguages

29Object-orientedprototype-basedlanguages

30Off-siderulelanguages

31Procedurallanguages

32Reflec:velanguages

33Rule-basedlanguages

34Scrip:nglanguages

35Stack-basedlanguages

36Synchronouslanguages

37Syntaxhandlinglanguages

38Visuallanguages

39Wirthlanguages

40XML-basedlanguages

FromWikipedia20171 Arraylanguages2 Assemblylanguages3 Authoringlanguages4 Constraintprogramminglanguages5 Begin...Endlanguages6 Commandlineinterfacelanguages7 Compiledlanguages8 Concurrentlanguages9 Curly-bracketlanguages10 Dataflowlanguages11 Data-orientedlanguages12 Data-structuredlanguages13 Decisiontablelanguages14 Declara:velanguages15 Embeddablelanguages15.1 Insourcecode15.1.1 Serverside15.1.2 Clientside15.2 Inobjectcode16 Educa:onallanguages17 Esotericlanguages18 Extensionlanguages19 Fourth-genera:onlanguages20 Func:onallanguages20.1 Pure20.2 Impure21 Hardwaredescrip:onlanguages21.1 HDLsforanalogcircuitdesign21.2 HDLsfordigitalcircuitdesign22 Impera:velanguages23 Interac:vemodelanguages24 Interpretedlanguages25 Itera:velanguages26 Languagesbymemorymanagementtype26.1 Garbagecollectedlanguages26.2 Languageswithmanualmemorymanagement27 List-basedlanguages–LISPs28 LiWlelanguages29 Logic-basedlanguages30 Machinelanguages31 Macrolanguages31.1 Textualsubs:tu:onmacrolanguages31.2 Applica:onmacrolanguages32 Metaprogramminglanguages33

Mul:paradigmlanguages34 Numericalanalysis35 Non-English-basedlanguages36 Object-orientedclass-basedlanguages36.1 Mul:pledispatch36.2 Singledispatch37 Object-orientedprototype-basedlanguages38 Off-siderulelanguages39 Procedurallanguages40 Reflec:velanguages41 Rule-basedlanguages42 Scrip:nglanguages43 Stack-basedlanguages44 Synchronouslanguages45 Syntaxhandlinglanguages46 Transforma:onlanguages47 Visuallanguages48 Wirthlanguages49 XML-basedlanguages

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Classifica:onofProgrammingLanguages•  Therearedifferentwaysofgroupingprogramminglanguagestogether

– Byabstrac:onlevel–  Lowlevel,highlevel,veryhighlevel

– Bydomain–  businesslanguages,scien:ficlanguages,AIlanguages,systemslanguages,scrip:ng

languages,XML-basedlanguages

– Bygenerality–  generalpurposevs.specialpurpose

– Byimplementa:onmethods–  Interpretedvs.compiled

– Byparadigm–  aparadigmisawayofviewingprogramming,basedonunderlyingtheoriesofproblem

solvingstyles–  programminglanguagesgroupedinthesameparadigmaresimilarintheirapproachto

problemsolving–  impera:ve,object-oriented,logic-based,func:onal,etc.

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Byabstractlevelfromthemachine

• Low-levellanguages– Machinelanguages,assemblylanguages

• High-levellanguages– Algol,Pascal,C++,Java,C#,etc.

• Veryhigh-levellanguages– Usuallylimitedtoaveryspecificapplica:on.– Duetothislimita:oninscope,theymightusesyntaxthatisneverusedinotherprogramminglanguages.

– E.g.,Prolog,SQL• Notethattheterms"high-level"and"low-level"areinherentlyrela:ve.

– OriginallyCwasconsideredhighlevelbutnowadaysmanyprogrammersmightreferCaslowlevel,asits:llsallowsmemorytobeaccessedbyaddress,andprovidesdirectaccesstotheassemblylevel.

Classification by level

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High–levelvs.lowlevellanguages•  “High-level”referstothehigherlevelofabstrac:onfrommachinelanguage.

–  itdoesnotimplythatthelanguageissuperiortolow-levelprogramminglanguages.•  Characteris:cs:

–  High-levellanguagesdealwithvariables,arraysandcomplexarithme:corbooleanexpressions;

–  “low-level”languagesdealwithregisters,memoryaddressesetc.•  Prosandcons

–  High-levellanguagesmakeprogrammingsimpler;–  whilelow-levellanguagesproducemoreefficientcode;–  codewhichneedstorunefficientlymaybewriWeninalower-levellanguage.

thought

Languages machine

High Level Language

Assembly Language

Machine Language

Very high level Language

Closer to humans


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Lowvs.highlevellanguages

•  unsignedintgcd(unsignedinta,unsignedintb){if(a==0&&b==0)b=1;elseif(b==0)b=a;elseif(a!=0)while(a!=b)if(a<b)b-=a;elsea-=b;returnb;}

; Author: Paul Hsieh gcd: neg eax je L3 L1: neg eax xchg eax,edx L2: sub eax,edx jg L2 jne L1 L3: add eax,edx jne L4 inc eax L4: ret

; WATCOM C/C++ v10.0a output gcd: mov ebx,eax mov eax,edx test ebx,ebx jne L1 test edx,edx jne L1 mov eax,1 ret L1: test eax,eax jne L2 mov eax,ebx ret L2: test ebx,ebx je L5 L3; cmp ebx,eax je L5 jae L4 sub eax,ebx jmp L3 L4: sub ebx,eax jmp L3 L5: ret


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Javaandbytecode

publicclassHello{

publicsta:cvoidmain(String[]a){

System.out.println("Hello");

}

}

Btw,Howtoviewthebytecode?

javap–cHello

publicclassHelloextendsjava.lang.Object{

publicHello();

Code:

0:aload_0

1:invokespecial#1;//Methodjava/lang/Object."<init>":()V

4:return

publicsta:cvoidmain(java.lang.String[]);

Code:

0:getsta:c#2;//Fieldjava/lang/System.out:Ljava/io/PrintStream;

3:ldc#3;//StringHello

5:invokevirtual#4;//Methodjava/io/PrintStream.println:(Ljava/lang/String;)V

8:return

}


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ClassifyingLanguagesbyDomain:Scien:fic•  Historically,languageswereclassifiedmostoxenbydomains.

– Scien:fic,Business(DataProcessing),AI,System,Scrip:ng.

•  Thefirstdigitalcomputerwasusedandinventedforscien:ficapplica:on.

•  Thefirsthighlevelprogramminglanguageisforscien:fic(engineering)applica:on

– Simpledatastructuresbutlargenumberoffloa:ng-pointarithme:ccomputa:ons.

•  Thisisincontrasttobusinessapplica:onthatrequiresstronglanguagesupportforfilemanipula:on,tablelookup,reportgenera:on,etc.

•  Oxenefficient

•  Examplelanguages:Fortran,Algol.

Classification by dom

ain

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ClassifyingLanguagesbyDomain:Business

• Business(some:mesa.k.a.dataprocessing)– Languagefeaturesemphasizefilehandling,tablelookup,reportgenera:on,etc.

– Weaklanguagesupportformathfunc:ons,graphics,recursion,etc.

– Examplelanguage:COBOL(COmmonBusinessOrientedLanguage),ini:alversionin1960.

– Nowmostlyhandledbydatabasesystems,spreadsheets,etc.


ain

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ClassifyingLanguagesbyDomain:Ar:ficialIntelligence

• Highlevelofabstrac:onforsymbolmanipula:on,ratherthannumericcomputa:on

– Symbolicmanipula:on:symbols,consis:ngofnamesratherthannumbers,arecomputed

– Linkedlists(oxenbuilt-in)ratherthanarray,declara:ve,recursionratherthanloop,self-modifica:on,etc.

• Oxen(very)high-level,inefficient

• Examplelanguages:– Lisp(LIStProcessing),Scheme,ML,Miranda,etc.

– Prolog(Frenchfor“logicprogramming”),etc.


ain

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ClassifyingLanguagesbyDomain:Systems

•  Languagesforsystemsoxware– Systemsoxwareincludesopera:ngsystemsandprogrammingsupporttools.

•  Languagesupportforhardwareinterface,opera:ngsystemcalls,directmemory/deviceaccess,etc.

•  LiWleornodirectsupportforprogrammerdefinedabstrac:on,complextypes,symbolmanipula:on

•  Low-level,veryefficient

•  Veryfewrestric:onsonprogrammer(accesstoeverything)

•  Examplelanguages:C,Go–  Lowlevel,efficient,fewsafetyrestric:ons.


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ClassifyingLanguagesbyDomain:Scrip:ng

•  Scrip:ng:connec:ngdiversepre-exis:ngcomponentstoaccomplishanewrelatedtask.

•  Ini:allydesignedfor"scrip:ng"theopera:onsofacomputer.–  Earlyscriptlanguageswereoxencalledbatchlanguagesorjobcontrollanguages(ShellScript),suchas.bat,csh.

rmA3Scanner.*A3Parser.*A3User.classA3Symbol.*A3.outputjavaJLex.MainA3.lexjavajava_cup.Main-parserA3Parser-symbolsA3Symbol<A3.cupjavacA3.lex.javaA3Parser.javaA3Symbol.javaA3User.javajavaA3UsermoreA3.output

–  Ascriptismoreusuallyinterpretedthancompiled,butnotalways.


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Scrip:nglanguage(2)

• Nowscrip:nglanguagescanbequitesophis:cated,beyondautoma:ngcomputertasks;

– JavaScript,PHP:Webprogramming;

– Perl:textprocessing,butlaterdevelopedintoageneralpurposelanguages;

• Characteris:cs:– Favorrapiddevelopmentoverefficiencyofexecu:on;

– Oxenimplementedwithinterpretersratherthancompilers;

– Strongatcommunica:onwithprogramcomponentswriWeninotherlanguages.


ain

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XML-basedlanguages

• Languagesthat– OperateonXMLdocuments

– UsuallythesyntaxofthelanguageisXML

• Examples– XPath– XQuery– XSLT


ain

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ClassifyingLanguagesbyGenerality

• GeneralPurpose– Languageswithfeaturesthatallowimplementa:onofvirtuallyanyalgorithm

– Roughlyuniformlevelofabstrac:onoverlanguagefeatures

– C,C++,Java,Delphi,etc.,etc.,etc.

• SpecialPurpose– Languageswithaveryrestrictedsetoffeatures– Highlevelofabstrac:onamongfeatures

– SQL,MATLAB,R,lex/yacc(JLex/JavaCup),etc.etc.

Classification by generality

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MATLAB

• Matrixmanipula:on

• Plo|ng

• Widelyusedbyengineersandappliedsta:s:cians

• Examplex=1:10;

y=x.^2

plot(y)

• No:cethereisnoexplicitloop!

Classification by generality

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figure

[X,Y]=meshgrid(-8:.5:8);

R=sqrt(X.^2+Y.^2)+eps;

Z=sin(R)./R;mesh(X,Y,Z)

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Classifyinglanguagesbyimplementa:onmethods

• Compila:on:transla:nghigh-levelprogram(sourcelanguage)intomachinecode(machinelanguage)

– Slowtransla:on,fastexecu:on

• PureInterpreta:on:Programsareinterpretedbyanotherprogramknownasaninterpreter

– Ittakeslongertorunaprogramunderaninterpreterthantorunthecompiledcode.

• HybridImplementa:onSystems– Acompromisebetweencompilersandpureinterpreters

Classification by im

plementation m

ethods

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Compilation and execution

Output Data Input Data

Target Program

Abstract Program (Optimized)

Parse Tree Symbol Table

Source program

Code Optimization

Semantic Analysis

Loader / Linker Code Generation

Computer

Lexical Analysis (scanning)

Syntactic Analysis (parsing)

compiler

Token Sequence

Abstract Program (Intermediate code)

Object Program (Native Code)


plementation m

ethods

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Implementa:onmethods:Compila:on

• Compila:onprocesshasseveralphases:– Lexicalanalysis:convertscharactersinthesourceprogramintolexicalunits

– Syntaxanalysis:transformslexicalunitsintoparsetreeswhichrepresentthesyntac:cstructureofprogram

– SemanDcsanalysis:checktypesetc;generateintermediatecode

– CodegeneraDon:machinecodeisgenerated

• Addi:onalCompila:onTerminologies– Linkingandloading:Whenloadingcompiledprogramsintocomputermemory,theyarelinkedtotherelevantprogramresources,andthenthefullyresolvedcodesareintocomputermemory,forexecu:on.


plementation m

ethods

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Runjava-verbosesol:~/440>java-verboseHello

[Opened/usr/jdk/instances/jdk1.5.0/jre/lib/rt.jar]

[Opened/usr/jdk/instances/jdk1.5.0/jre/lib/jsse.jar]

[Opened/usr/jdk/instances/jdk1.5.0/jre/lib/jce.jar]

[Opened/usr/jdk/instances/jdk1.5.0/jre/lib/charsets.jar]

[Loadedjava.lang.Objectfrom/usr/jdk/instances/jdk1.5.0/jre/lib/rt.jar]

[Loadedjava.io.Serializablefrom/usr/jdk/instances/jdk1.5.0/jre/lib/rt.jar]

[Loadedjava.lang.Comparablefrom/usr/jdk/instances/jdk1.5.0/jre/lib/rt.jar]

[Loadedjava.lang.CharSequencefrom/usr/jdk/instances/jdk1.5.0/jre/lib/rt.jar]

[Loadedjava.lang.Stringfrom/usr/jdk/instances/jdk1.5.0/jre/lib/rt.jar]

[Loadedjava.lang.reflect.GenericDeclara:onfrom/usr/jdk/instances/jdk1.5.0/jre/lib/rt.jar]

[Loadedjava.lang.reflect.Typefrom/usr/jdk/instances/jdk1.5.0/jre/lib/rt.jar]

[Loadedjava.lang.reflect.AnnotatedElementfrom/usr/jdk/instances/jdk1.5.0/jre/lib/rt.jar]

[Loadedjava.lang.Classfrom/usr/jdk/instances/jdk1.5.0/jre/lib/rt.jar]

[Loadedjava.lang.Cloneablefrom/usr/jdk/instances/jdk1.5.0/jre/lib/rt.jar]

[Loadedjava.lang.ClassLoaderfrom/usr/jdk/instances/jdk1.5.0/jre/lib/rt.jar]

[Loadedjava.lang.Systemfrom/usr/jdk/instances/jdk1.5.0/jre/lib/rt.jar]

…(hundredsofrelatedclasses)

[LoadedHellofromfile:/global/fac2/jlu/440/]

Hello

[Loadedjava.lang.Shutdownfrom/usr/jdk/instances/jdk1.5.0/jre/lib/rt.jar]

[Loadedjava.lang.Shutdown$Lockfrom/usr/jdk/instances/jdk1.5.0/jre/lib/rt.jar]

public class Hello { public static void main(String [] a){ System.out.println("Hello"); } }


plementation m

ethods

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Interpretedlanguage

•  Programsareexecutedfromsourceform,byaninterpreter.–  manylanguageshavebothcompilersandinterpreters,includingLisp,Scheme,BASIC,andPython.

•  Disadvantages:–  Muchslower

–  Real:metransla:on;–  Ini:ally,interpretedlanguageswerecompiledline-by-line;eachlinewas

compiledasitwasabouttobeexecuted,andifalooporsubrou:necausedcertainlinestobeexecutedmul:ple:mes,theywouldberecompiledevery:me.

–  Requiremorespace.–  Sourcecode,symboltable,…

•  Advantageofinterpretedlanguages–  Easyimplementa:onofsource-leveldebuggingopera:ons,becauserun-:meerrorscanrefertosource-levelunits

–  E.g.,ifanarrayindexisoutofrange,theerrormessagecaneasilyindicatethesourcelineandthenameofthearray.

–  Itcantakeless:metointerpretitthanthetotal:merequiredtocompileandrunit.Thisisespeciallyimportantwhenprototypingandtes:ngcodewhenanedit-interpret-debugcyclecanoxenbemuchshorterthananedit-compile-run-debugcycle.(e.g.,csh)


plementation m

ethods

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Hybridimplementa:on

•  Acompromisebetweencompilersandpureinterpreters

– Translatehigh-levellanguageprogramintointermediatelanguagedesignedtoalloweasyinterpreta:on;

– Fasterthanpureinterpreta:onsincethesourceistranslatedonlyonce.

– Example:Java.–  Providesportabilitytoanymachinethat

supporttheintermediatelanguage

– Otherlanguagethatuseshybridimplementa:on?

•  Canwemakeitfaster?–  JIT(Just-In-Time)compiler


plementation m

ethods

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JITcompiler

•  Ajust-in-:mecompiler(JIT)improvesperformanceofbytecodesbycompilingthemintona:vemachinecodebeforeexecu:ngthem.

– Translatesbytecodes(orotherintermediatecode)intomachineinstruc:onsastheyarereadin;

– Performsadegreeofop:miza:on;

– Theresul:ngprogramisthenrun;

– Partsoftheprogramthatdon'texecutearen'tcompiled,soaJITdoesn'twaste:meop:mizingcodethatneverruns.

– Themachineinstruc:onsaren'tsavedanywhereexceptinmemory.Thenext:metheprogramisrun,thebytecodesaretranslatedintomachinecodeonceagain.–  Theresultisthatthebytecodesares:llportable,–  andtheytypicallyrunmuchfasterthantheywouldinanormalinterpreter.

•  IntroducedinSunJRE1.2


plementation m

ethods

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Review

• Classifyinglanguagesby– Abstrac:onlevel(lowlevel,highlevel,veryhighlevel)– Domain(scien:fic,dataprocessing,scrip:ng…)

– Generalpurposevs.specialpurpose– Implementa:onmethods(interpreter,compiler,hybrid)

–  compila:onprocess

– ……– Paradigms

• “languageshapesthewaywethink,anddetermineswhatwecanthinkabout.“–B.L.Whorf

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ProgrammingParadigms

• Astyleofprogramming

• Aprogrammingparadigmprovidestheviewthattheprogrammerhasoftheexecu:onoftheprogram.

– Object-orientedprogramming:programmersthinkofaprogramasacollec:onofinterac:ngobjects;

– Func:onalprogramming:aprogramcanbethoughtofasasequenceofstatelessfunc:onevalua:ons.

• Manyprogrammingparadigmsareaswell-knownforwhattechniquestheyforbidasforwhattheyenable.

– Purefunc:onalprogrammingdisallowstheuseofside-effects;

– Structuredprogrammingdisallowstheuseofgoto.

Classification by paradigm

s

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Paradigmsandlanguages•  Somelanguagesaredesignedtosupportonepar:cularparadigm

–  Smalltalksupportsobject-orientedprogramming–  Schemesupportsfunc:onalprogramming.

•  Aprogramminglanguagecansupportmul:pleparadigms.–  E.g.,Javaisdesignedtosupportimpera:veprogramming,object-orientedprogramming,andgenericprogramming.

•  Aprogramminglanguageadvocates(notenforce)aparadigm(s).–  Programmersdecidehowtobuildaprogramusingthoseparadigmelements.–  E.g.,onecanwriteapurelyimpera:veprograminJava(notencouraged)–  ThefollowingsareunstructuredandstructuredprogramwriWeninthesamelanguage

dim i for i = 1 to 10 print i & " squared = " & square(i) next print "Program Completed." function square(i) square = i * i end function

10 dim i 20 i = 0 30 i = i + 1 40 if i <> 10 then goto 90 50 if i = 10 then goto 70 60 goto 30 70 print "Program Completed." 80 end 90 print i & " squared = " & i * i 100 goto 30


s

paradigms languages

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Exampleparadigms

• Structuredprogrammingvs.Unstructuredprogramming

• Impera:veprogrammingvs.Declara:veprogramming

• Object-orientedprogramming

• AspectOrientedProgramming

• Func:onalprogramming

• Logicprogramming

• Serviceorientedprogramming


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Someprogrammingparadigms•  Impera:ve:

–  howdowesolveaproblem(whatstepsdoesasolu:onhave)?

•  Logic-based:–  whatistheproblemtobesolved?(Thelanguageimplementa:ondecideshowtodoit.)

•  Func:onal:–  whatsimpleopera=ons(func=ons)canbeappliedtosolveaproblem,howaretheymutuallyrelated,andhowcantheybecombined?

•  Object-oriented:– Whatobjectsplayrolesinaproblem,whatcantheydo,andhowdotheyinteracttosolvetheproblem?

•  Aspect-oriented:– Whataretheconcernsandcrosscu|ngconcerns?Howtoallowtheconcernsinteractwitheachother?

Classification by program

ming paradigm

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Structuredvs.unstructuredprogramming•  Unstructuredprogramming:Allcodeiscontainedinasinglecon:nuousblock.

–  Havetorelyonexecu:onflowstatementssuchasGoto,usedinmanylanguagestojumptoaspecifiedsec:onofcode.

–  Complexandtangled,difficulttoreadanddebug;–  Unstructuredprogrammingresultsinspaghe|code–  Discouragedinprogramminglanguagesthatsupportanykindofstructure.

•  anexampleSpaghe|codeinBASIC:10dimi20i=030i=i+140ifi<>10thengoto9050ifi=10thengoto7060goto3070print"ProgramCompleted."80end90printi&"squared="&i*i100goto30


ming paradigm

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Structuredvs.unstructured•  Structuredprogramming:

–  Programma:ctasksaresplitintosmallersec:ons(knownasfunc:onsorsubrou:nes)thatcanbecalledwhenevertheyarerequired.

–  RemoveGOTOstatements;–  Singleentry(andsingleexit)foreachprogramsec:on.

•  Consider:–  IsJavaastructuredprogramminglanguage?–  ComparedwithC++,whichoneismorestructured?

•  HereisanexampleSpaghe|codeandstructuredcodeinBASIC:

10dimi20i=030i=i+140ifi<>10thengoto9050ifi=10thengoto7060goto3070print"ProgramCompleted."80end90printi&"squared="&i*i100goto30

•  Canweturnallunstructuredcodetostructuredone?

dimifori=1to10printi&"squared="&square(i)nextprint"ProgramCompleted."func:onsquare(i)square=i*iendfunc:on


ming paradigm

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Structuredprogramming•  Structuredprogramtheorem

•  Anyprogramcanbegoto-free(1966,BöhmandJacopini,CACM)– anyprogramwithgotoscouldbetransformedintoagoto-freeforminvolvingonly–  Sequen:alcomposi:on–  choice(IFTHENELSE)and–  loops(WHILEcondi:onDOxxx),–  possiblywithduplicatedcodeand/ortheaddi:onofBooleanvariables(true/false

flags).

C

S

Y N S2

C

S1

Y N

S1 S2


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Impera:vevs.declara:ve•  Impera:ve:aprogrammingparadigmthatdescribescomputa:onintermsofaprogramstateandstatementsthatchangetheprogramstate.

–  Inmuchthesamewayastheimpera:vemoodinnaturallanguagesexpressescommandstotakeac:on,impera:veprogramsareasequenceofcommandsforthecomputertoperform.

– DerivedfromVonNeumannmachine– Acomputerfunc:onsbyexecu:ngsimpleinstruc:onsoneaxeranother–  Impera:velanguagesmirrorthisbehaviourataslightlyhigherlevelofabstrac:onfrommachine:–  theprogrammerspecifiesopera:onstobeexecutedandspecifiestheorderof

execu:ontosolveaproblem–  theimpera:velanguageopera:onsarethemselvesjustabstrac:onsofsome

sequenceoflower-levelmachineinstruc:ons– Programmermusts:lldescribeindetailhowaproblemistobesolved(i.e.,allofthestepsinvolvedinsolvingtheproblem)

• Mostofthelanguagesweusesupportimpera:veparadigm,whichincludeassembly,Fortran,Algol,Ada,Pascal,C,C++,etc.,etc.


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Impera:vevs.declara:ve

•  Aprogramis"declara:ve"ifitdescribeswhatsomethingis,ratherthanhowtocreateit.

–  Impera:veprogramsmakethealgorithmexplicitandleavethegoalimplicit;

– Declara:veprogramsmakethegoalexplicitandleavethealgorithmimplicit.

•  Examplesofdeclara:velanguages:– Func:onalprogramminglanguages,Logicprogramminglanguages,SQL.

•  Twomajordifferencesbetweenimpera:veanddeclara:veprogramming:– Assignmentstatement;

– Orderofexecu:on.


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Declara:vevs.Impera:ve:Assignment

•  Impera:velanguage:– basedontheconceptofvariablesnameswhichcanbeassociatedwithchangeablevaluesthroughexpressions.

– differentvaluesarecon:nuallyassociatedwithapar:cularvariablenameisreferredtoasdestruc:veassignment-eachfreshassignmentobliteratestheexis:ngvalue.

•  Declara:velanguage:– variablescanonlyeverhaveonevalue"assigned"tothemandthisvaluecannotbealteredduringaprogram'sexecu:on.

– Werefertothisasnon-destruc:veassignment.

•  Codenotallowedindeclara:veprogramming:IntX=10;…X=11;


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Declara:vevs.impera:ve:orderofexecu:on

•  Impera:velanguage:–  Valueofavariablecanbechanged;–  orderofexecu:oniscrucial.–  Avariable'svaluemaybechangedbeforethatvariableisusedinthenextexpression,i.e.impera:veexpressionshavesideeffects.

–  commandscanonlybeunderstoodinthecontextofthepreviouscomputa:on.

•  Declara:velanguage–  Thevaluesassociatedwithvariablenamescannotbechanged.–  theorderinwhichdefini:onsarecalleddoesnotmaWer,i.e.theyareorderindependent.–  declara:vedefini:onsdonotpermitsideeffects,i.e.thecomputa:onofonevaluewillnoteffectsomeothervalue.

–  declara:veprogramsmustbeexecutedinsomeorder,buttheordershouldnotaffectthefinalresult.

–  programstatementsareindependentofthecomputa:onalcontext.

•  Examplex=f(y)+f(y)*f(y);èz=f(y);x=z+z*z;


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Exampleofimpera:veanddeclara:veprogramming

voidinser:onSort(int[]A){intj;for(inti=1;i<A.length;i++){inta=A[i];for(j=i-1;j>=0&&A[j]>a;j--)A[j+1]=A[j];A[j+1]=a;}

}

fun insertsort [] = [] | insertsort (x::xs) = let fun insert (x:real, []) = [x] | insert (x:real, y::ys) = if x<=y then x::y::ys else y::insert(x, ys) in insert(x, insertsort xs) end;

•  Declarative programming: •  Declare what to do, but not how to do it; •  Don’t change values of variables; •  No loop constructs; •  Execution sequence is not specified.


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Func:onalprogramming

•  Aproblemissolvedastheevalua:onofafunc:on– Aprogramconsistsofasetoffunc:ondefini:ons,whereafunc:onissimplyamappingfromelementsofonesettoelementsofanotherset

– Programexecu:onconsistsofevalua:ngatop-levelfunc:on(i.e.,applyingafunc:ontospecifiedelementsofaset)

– Thelanguageitselfisthefunc:onevaluator;theevalua:onmechanismisnotvisibletotheprogrammer(majorproceduralabstrac=on!)

– Novariables,noassignment

–  “everythingisafunc:on”–  canapplyfunc:onstofunc:onstoo!

•  Lisp,Scheme,CommonLisp,ML,CAML,Haskell


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Func:onalprogramming

• Trulydifferentfromimpera:velanguages:– Cannotassignvaluestovariablesorchangeavariable’svalue;– Noloopconstruct;– Orderofexecu:onofstatementssupposedtobeirrelevant(andunknown)

funinsertsort[]=[]|insertsort(x::xs)=letfuninsert(x:real,[])=[x]|insert(x:real,y::ys)=ifx<=ythenx::y::yselsey::insert(x,ys)ininsert(x,insertsortxs)end;


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Declara:veprogrammingexample:SQL•  Considerthefollowingquery:

–  customers(id,name,phone)–  Orders(o-id,c-id,product,price,date)

SELECTproduct,price,dateFROMcustomers,ordersWHEREcustomers.id=orders.c-idAND customers.name=“john”

•  Itdeclareswhatwewant.Doesnotspecifyhowtoimplementit.

–  e.g.whichcondi:ontorunfirst?•  Therearemanydifferentwaystoimplement.

–  Anaïveonewouldbeveryexpensive(constructtheCartesianproductofthetwotables,jointwoidsfirst)wouldbeveryexpensive;

•  Queryengine(compiler)willtakecareoftheseimplementa:onissue.

•  Conclusions:–  Declara:veprogrammingfocusonhigherlevelofabstrac:on;

–  Itismoredifficulttoimplement.

id name phone 123 Mike 2533000

124 john 2345678

125 Vivian 123 4567

O-id C-id product price Date

01 123 Coke 1.00 06-01-11

02 124 water 6 06-01-02

03 123 juice 4 06-01-03

04 125 milk 3.8 06-01-01

id name Phone O-id C-id Product price date

123 Mike 2533000 01 123 Coke 1.00 ..

123 Mike 2533000 03 123 Juice 4 ..

124 john 2345678 02 124 Water 6 ..

125 Vivian 123 4567 04 125 Wilk 3.8 ..


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Logicprogramming

• Aproblemissolvedbysta:ngtheproblemintermsoflogic(usuallyfirst-orderlogic,a.k.a.predicatecalculus)

– aprogramconsistsofknownfactsoftheproblemstateaswellasrulesforcombiningfacts(andpossiblyotherrules)

– programexecu:onconsistsofconstruc:ngaresolu=onproofofastatedproposi:on(calledthegoal)

– Atheoremproverisbuilt-intothelanguageandisnotvisibletotheprogrammer(majorproceduralabstrac=on!)

• Prolog,Datalog


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43

Prolog

•  Trulydifferentfromimpera:velanguages– Cannotassignvaluestovariablesorchangeavariable’svalue;– Noloopconstruct;– Orderofexecu:onofstatementssupposedtobeirrelevant(andunknown),theore:cally.

isort([],[]).isort([X|UnSorted],AllSorted):-isort(UnSorted,Sorted),insert(X,Sorted,AllSorted).insert(X,[],[X]).insert(X,[Y|L],[X,Y|L]):-X=<Y.insert(X,[Y|L],[Y|IL]):-X>Y,insert(X,L,IL).


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44

ClassifyingLanguagesbyParadigm

•  AllisaboutABSTRACTION•  Aprogramconsistsofdataandprocedure.

•  Thereareproceduralabstrac:onanddataabstrac:on•  Controlinfunc:onal/logicparadigmsisabstractedtothepointofnonexistence

•  InOOyous:llhaveloops,func:ons(methods),blocksofsequen:alcodeinwhichorderofexecu:onmaWers,etc.

object-oriented

functional; logic-based

imperative

mor

e pr

oced

ural

abs

tract

ion

more data abstraction


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45

Object-Orientedprogramming•  Programiscomposedofacollec:onofindividualunits,orobjects,thatactoneachother,

–  Tradi:onal(impera:ve)view:aprogramisalistofinstruc:onstothecomputer.

•  Objectsasaprogrammingen::eswerefirstintroducedinSimula67,aprogramminglanguagedesignedformakingsimula:ons.

•  TheSmalltalklanguage,whichwasdevelopedatXeroxPARC,introducedthetermObject-orientedprogrammingtorepresentthepervasiveuseofobjectsandmessagesasthebasisforthecomputa:on.

•  Aproblemissolvedbyspecifyingobjectsinvolvedintheproblem–  ObjectsinOOcorrespondroughlytoreal-worldobjectsintheproblem–  Objectsareinstancesofclasses(abstractdatatypes)–  Classesarearrangedinhierarchies,withsubclassesinheri:ngproper:esofsuperclasses–  Opera:ons(calledmethods)aredefinedspecifictoeachclass–  Problemsolvingisaccomplishedthroughmessagepassingbetweenobjects(amessageisacalltoamethodofaspecificobject)

•  OOlanguages:Simula,Smalltalk,C++,Java,C#etc.


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Paradigms:Aspect-OrientedProgramming

• Alessgeneralsolu:on– AspectOrientedprogramminglanguageshouldbeusedtogetherwithotherlanguages;

– Baselanguagedefinesfunc:onality– AOPdescribescrosscu|ngconcerns.

• Simpleandpowerful

• Becamepopularandwide-spread

• Manyapproaches,manyimplementa:ons

• AlsocalledAOSD,Aspect-OrientedSoxwareDevelopment

• Mostfamous:AspectJ


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Programminglanguagehistory

Createdbywordle.net,fromthetextinthisslide

03-60-440:Programminglanguagehistory

Tower of Babel, CACM cover, Jan. 1961

Babel: 1.  a city in Shinar where the

building of a tower is held in Genesis to have been halted by the confusion of tongues

2.  a confusion of sounds or voices

3.  a scene of noise or confusion

--Webster

50

Evolu:onofprogramminglanguages

Imperative Functional

-10 -8 -6 -4 -2 0 2 4 6 8 10-10

-8

-6

-4

-2

0

2

4

6

8

10

JavaScript

Java

ObjectiveC

Python

RubyNone

PHP

C

HTML

Go

CSS

C++Swift

ShellC#

VimLCoffeeScript

Clojure

Scala

Emacs-Lisp

Perl

Lua

Haskell

Erlang

TeX

Rust

Makefile

Jupyter-Notebook

TypeScript

Groovy

ActionScript

ROCaml

Assembly

Elixir

PowerShell

Groff

Haxe

ApacheConf

XSLT

Processing

Julia

Objective-J

Kotlin

Common-Lisp

LiveScript

Eagle

Dart ObjectiveC++

Arduino

Nginx

Matlab

D

PostScript

Perl6

Scheme

Batchfile

F#

Vala

Pascal

XML

IDL

MoonScript

wisp

ModelicaYacc

NSIS

PLpgSQL

Racket

AGS-Script

SQLPL

Mirah

Awk

GLSL

FORTRAN

Mathematica

Nix

PigLatin

Protocol-Buffer

Vue

Nimrod CMake

Crystal

KiCad

PureBasic

Cuda

Frege

nesC

Stan

Elm

Arc

Handlebars

RedQML

51Relations between languages derived from GitHub user interactions. Generated by Zhongpei Zhang and Jianguo Lu

52

FORTRAN(FormulaTranslator)

• Itisthefirsthighlevelprogramminglanguage– ThePreliminaryReport,1954,claimsthatFORTRANwillvirtuallyeliminatecodinganddebugging.

– DevelopedbyJohnBackus,atIBM.– Majorversions:FortranIIin1958,FortranIVin1961,Fortran77,Fortran95,Fortran2003(OOsupport).

• Ini:alversionsrelyheavilyonGOTOstatement;

• Itremainsthelanguageofchoiceforhighperformancenumericalcompu:nginscienceandengineeringcommuni:es

– Exampleapplica:ons:–  Weatherandclimatemodeling,solarsystemdynamics,simula:onofautocrashes.

53

ALGOL(ALGOrithmicLanguage)

•  defactostandardwaytoreportalgorithmsinprint

•  DesignedtoimproveFortran

•  JohnBackusdevelopedtheBackusNaurFormmethodofdescribingprogramminglanguages.

•  ALGOL60inspiredmanylanguagesthatfollowedit"ALGOL60wasagreatimprovementonitssuccessors.“Thefullquoteis"Hereisalanguagesofaraheadofits:me,thatitwasnotonlyanimprovementonitspredecessors,butalsoonnearlyallitssuccessors"--C.A.RHoare

procedureAbsmax(a)Size:(n,m)Result:(y)Subscripts:(i,k);valuen,m;arraya;integern,m,i,k;realy;commentTheabsolutegreatestelementofthematrixa,ofsizenbymistransferredtoy,andthesubscriptsofthis

elementtoiandk;beginintegerp,q;y:=0;i:=k:=1;forp:=1step1unDlndoforq:=1step1unDlmdoifabs(a[p,q])>ythenbeginy:=abs(a[p,q]);i:=p;k:=qendendAbsmax

54

TheoriginofOOP:SimulaandSmalltalk

• Simula67:– Developedin1960’s,byOle-JohanDahl– Simula:onofcomplexsystems

– Introducedobjects,classes,andinheritance.

• Smalltalk:– DevelopedatXeroxPARC,ini:allybyAlanKay,in1970’s.– Firstfullimplementa:onofanobject-orientedlanguage(dataabstrac:on,inheritance,anddynamictypebinding)

– Pioneeredthegraphicaluserinterfacedesign– PromotedOOP

55

Java(andcomparisonwithC++)

•  DerivedfromC++.Smaller,simpler,andmorereliable– e.g.,nopointers,nomul:pleinheritance,automatedgarbagecollec:on.

•  Designphilosophy–  Javawascreatedtosupportnetworkingcompu:ng,embeddedsystems.

– C++wascreatedtoaddOOtoC.Supportsystemsprogramming.

•  Versionhistory– 1.0:1996– 1.2:1998,IntroducedSwing,JIT– 1.4:2002,assert,regularexpression,XMLparsing

– 1.5(5):2004,generics,enumera:on

– 6:Dec2006webservicesupport(JAXWS)

– 7:July2011– 8:2014,lambdaexpression,higherorderfunc:ons

56

JavaandC#

• ThesyntaxofbothlanguagesissimilartoC++,whichwasinturnderivedfromC.

• Bothlanguagesweredesignedtobeobjectorientedfromthegroundup;unlikeC++,theywerenotdesignedtobecompa:blewithC.

• Bothprovideparametricpolymorphismbygenericclasses.

• Bothlanguagesrelyonavirtualmachine.– BoththeJavaVMandthe.NETpla�ormop:mizecodeatrun:methroughjust-in-:mecompila:on(JIT).

• Bothincludegarbagecollec=on.• Bothincludeboxingandunboxingofprimi:vetypes,allowingnumberstobehandledasobjects.

• Bothincludeforeach,anenhancediterator-basedforloop.

57

Foreachstatement:anexampleofabstrac:on

•  Javaitera:on:tradi:onalway(before2004)Listnames=newArrayList();names.add("a");names.add("b");names.add("c");

for(Iteratorit=names.iterator();it.hasNext();){Stringname=(String)it.next();System.out.println(name.charAt(0));}

•  Java1.5:for(Stringname:names)System.out.println(name.charAt(0));

•  Newloopstructureismoredeclara:ve.

58

XMLprogramming

• XPath• XQuery• XSLT• JSP• Webserviceprogramming

59

IDE(IntegratedDevelopmentEnvironment)

• IDEforJava:Eclipse

60

Turingaward(Nobelprizeincomputerscience)recipientsrelevanttothiscourse

Year Recipient Contribution to programming languages 1966 Alan Jay Perlis Compiler and Algol 1971 John McCarthy Lisp 1972 Edsger Dijkstra Algol, Structured programming 1977 John Backus Fortran, BNF 1980 C.A.R. Hoare Axiomatic semantics 1983 Ken Thompson and

Dennis M. Ritchie c and unix

1984 Niklaus Wirth Modula, PASCAL 2001 Ole-Johan Dahl and

Kristen Nygaard SIMULA, OO

2003 Alan Kay SMALLTALK, OO 2005 Peter Naur Algol, BNF

Languagepopularityoveryears

61

•  Measured by how often language tutorials are searched on Google. •  This is the trend in USA. •  You can get the trend of other languages from

http://pypl.github.io/PYPL.html?country=US

Popularityworldwide

62

63

Popularityofprogramminglanguages

• Fromlangpop.comSept2010.MeasuredfromGoogleCode.

64

Popularityofprogramminglanguages

•  Thisisachartshowingcombinedresultsfromalldatasets

programmer

65

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