ARTIFICIAL INTELLIGENCE LANGUAGES · Artificial Intelligence Languages Subject 1.Subject...

ARTIFICIAL INTELLIGENCE ARTIFICIAL INTELLIGENCE ARTIFICIAL INTELLIGENCE ARTIFICIAL INTELLIGENCE ARTIFICIAL INTELLIGENCE ARTIFICIAL INTELLIGENCE ARTIFICIAL INTELLIGENCE ARTIFICIAL INTELLIGENCE

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DEPARTMENT OFDEPARTMENT OFDEPARTMENT OFDEPARTMENT OFCOMPUTER SCIENCE AND NUMERICAL ANALYSIS COMPUTER SCIENCE AND NUMERICAL ANALYSIS COMPUTER SCIENCE AND NUMERICAL ANALYSIS COMPUTER SCIENCE AND NUMERICAL ANALYSIS

LANGUAGESLANGUAGESLANGUAGESLANGUAGESLANGUAGESLANGUAGESLANGUAGESLANGUAGESTECHNICAL ENGINEERING IN MANAGEMENT COMPUTER SCIENCETECHNICAL ENGINEERING IN MANAGEMENT COMPUTER SCIENCETECHNICAL ENGINEERING IN MANAGEMENT COMPUTER SCIENCETECHNICAL ENGINEERING IN MANAGEMENT COMPUTER SCIENCE

TECHNICAL ENGINEERING IN SYSTEMS COMPUTER SCIENCETECHNICAL ENGINEERING IN SYSTEMS COMPUTER SCIENCETECHNICAL ENGINEERING IN SYSTEMS COMPUTER SCIENCETECHNICAL ENGINEERING IN SYSTEMS COMPUTER SCIENCE

SECOND YEARSECOND YEARSECOND YEARSECOND YEAR

FIRST FOURFIRST FOURFIRST FOURFIRST FOUR----MONTH PERIODMONTH PERIODMONTH PERIODMONTH PERIOD

ARTIFICIAL INTELLIGENCE LANGUAGESARTIFICIAL INTELLIGENCE LANGUAGESARTIFICIAL INTELLIGENCE LANGUAGESARTIFICIAL INTELLIGENCE LANGUAGESARTIFICIAL INTELLIGENCE LANGUAGESARTIFICIAL INTELLIGENCE LANGUAGESARTIFICIAL INTELLIGENCE LANGUAGESARTIFICIAL INTELLIGENCE LANGUAGES PROGRAMPROGRAMPROGRAMPROGRAMPROGRAMPROGRAMPROGRAMPROGRAM

FirstFirstFirstFirst part: part: part: part: SchemeSchemeSchemeScheme

Subject 1.Subject 1.Subject 1.Subject 1.---- Introduction to Scheme languageIntroduction to Scheme languageIntroduction to Scheme languageIntroduction to Scheme language

Subject 2.Subject 2.Subject 2.Subject 2.---- Expressions and FunctionsExpressions and FunctionsExpressions and FunctionsExpressions and Functions

Subject 3.Subject 3.Subject 3.Subject 3.---- Conditional Predicates and SentencesConditional Predicates and SentencesConditional Predicates and SentencesConditional Predicates and Sentences

Subject 4.Subject 4.Subject 4.Subject 4.---- Iteration and RecursionIteration and RecursionIteration and RecursionIteration and Recursion

Subject 5.Subject 5.Subject 5.Subject 5.---- Compound Data Types Compound Data Types Compound Data Types Compound Data Types

Subject 6.Subject 6.Subject 6.Subject 6.---- Data Abstraction Data Abstraction Data Abstraction Data Abstraction

2

Second part: Second part: Second part: Second part: PrologPrologPrologProlog


Subject 7.Subject 7.Subject 7.Subject 7.---- Reading and WritingReading and WritingReading and WritingReading and Writing

Subject 8.Subject 8.Subject 8.Subject 8.---- IntroductionIntroductionIntroductionIntroduction totototo Prolog languageProlog languageProlog languageProlog language

Subject 9.Subject 9.Subject 9.Subject 9.---- Basic Elements of PrologBasic Elements of PrologBasic Elements of PrologBasic Elements of Prolog

Subject 10.Subject 10.Subject 10.Subject 10.---- ListsListsListsLists

Subject 11.Subject 11.Subject 11.Subject 11.---- ReReReRe----evaluation and the “cut” evaluation and the “cut” evaluation and the “cut” evaluation and the “cut”

Subject 12.Subject 12.Subject 12.Subject 12.---- Input and OutputInput and OutputInput and OutputInput and Output

ARTIFICIAL INTELLIGENCE LANGUAGESARTIFICIAL INTELLIGENCE LANGUAGESARTIFICIAL INTELLIGENCE LANGUAGESARTIFICIAL INTELLIGENCE LANGUAGESARTIFICIAL INTELLIGENCE LANGUAGESARTIFICIAL INTELLIGENCE LANGUAGESARTIFICIAL INTELLIGENCE LANGUAGESARTIFICIAL INTELLIGENCE LANGUAGES PROGRAMPROGRAMPROGRAMPROGRAMPROGRAMPROGRAMPROGRAMPROGRAM

FirstFirstFirstFirst part: part: part: part: SchemeSchemeSchemeScheme

Subject 1.Subject 1.Subject 1.Subject 1.---- Introduction to Scheme languageIntroduction to Scheme languageIntroduction to Scheme languageIntroduction to Scheme language

Subject 2.Subject 2.Subject 2.Subject 2.---- Expressions and FunctionsExpressions and FunctionsExpressions and FunctionsExpressions and Functions

Subject 3.Subject 3.Subject 3.Subject 3.---- Conditional Predicates and SentencesConditional Predicates and SentencesConditional Predicates and SentencesConditional Predicates and Sentences

3

Subject 4.Subject 4.Subject 4.Subject 4.---- Iteration and RecursionIteration and RecursionIteration and RecursionIteration and Recursion

Subject 5.Subject 5.Subject 5.Subject 5.---- Compound Data Types Compound Data Types Compound Data Types Compound Data Types


Subject 7.Subject 7.Subject 7.Subject 7.---- Reading and WritingReading and WritingReading and WritingReading and Writing

Artificial Intelligence Languages Artificial Intelligence Languages Artificial Intelligence Languages Artificial Intelligence Languages Subject 1.Subject 1.Subject 1.Subject 1.---- Introduction to Scheme languageIntroduction to Scheme languageIntroduction to Scheme languageIntroduction to Scheme language

ContentsContentsContentsContents

1. Fundamental Characteristics of Functional Programming

2. Historic Summary of Scheme

4




1. Fundamental Characteristics of Functional ProgrammingFundamental Characteristics of Functional ProgrammingFundamental Characteristics of Functional ProgrammingFundamental Characteristics of Functional Programming


5


1.1.1.1. Fundamental Characteristics of Functional ProgrammingFundamental Characteristics of Functional ProgrammingFundamental Characteristics of Functional ProgrammingFundamental Characteristics of Functional Programming

� FunctionalFunctionalFunctionalFunctional Programming is a subtypesubtypesubtypesubtype of DeclarativeDeclarativeDeclarativeDeclarative Programming


6


� DeclarativeDeclarativeDeclarativeDeclarative Programming (1 / 2)Programming (1 / 2)Programming (1 / 2)Programming (1 / 2)

� ObjectiveObjectiveObjectiveObjective: Problem descriptionProblem descriptionProblem descriptionProblem description

“What”“What”“What”“What” problem must be resolved?

� NoticeNoticeNoticeNotice:


7


- It does notnotnotnot mind “how”how”how”how” the problem is resolved

- It avoidsavoidsavoidsavoids the implementation features.


� DeclarativeDeclarativeDeclarativeDeclarative Programming (2 / 2)Programming (2 / 2)Programming (2 / 2)Programming (2 / 2)

� FeaturesFeaturesFeaturesFeatures

� Expressivity

� Extensible: 10% - 90% rule


8

� Protection

� Mathematic Elegance

� TypesTypesTypesTypes:

� Functional Functional Functional Functional or Applicative Programming:

- Lisp, SchemeSchemeSchemeScheme, Haskell, …

� LogicLogicLogicLogic Programming: PrologPrologPrologProlog


1. Fundamental Characteristics of Functional Programming Fundamental Characteristics of Functional Programming Fundamental Characteristics of Functional Programming Fundamental Characteristics of Functional Programming

� PrinciplePrinciplePrinciplePrinciple of the “Pure”“Pure”“Pure”“Pure” FunctionalFunctionalFunctionalFunctional Programming

“The expression valueexpression valueexpression valueexpression value only depends ondepends ondepends ondepends on its subsubsubsub----expressionsexpressionsexpressionsexpressions values,

if such sub-expressions exist ”.

� NonNonNonNon collateral effectscollateral effectscollateral effectscollateral effects

9

The value of “a + b” onlyonlyonlyonly depends on “a” and “b”.

� The functionfunctionfunctionfunction term is used in its mathematicalmathematicalmathematicalmathematical sense.

� No instructionsNo instructionsNo instructionsNo instructions: programming withoutwithoutwithoutwithout assignments

� The impureimpureimpureimpure Functional programming allowsallowsallowsallows the

“assignment instruction”“assignment instruction”“assignment instruction”“assignment instruction”



� ProgramProgramProgramProgram structurestructurestructurestructure in FunctionalFunctionalFunctionalFunctional Programming

� The The The The programprogramprogramprogram is a function is a function is a function is a function composedcomposedcomposedcomposed of simpler functionsof simpler functionsof simpler functionsof simpler functions

� Function execution:Function execution:Function execution:Function execution:

� Receives the input dataReceives the input dataReceives the input dataReceives the input data: functions arguments or parameters

10

� Evaluates the expressionsEvaluates the expressionsEvaluates the expressionsEvaluates the expressions

� Returns the ResultReturns the ResultReturns the ResultReturns the Result: computed value of the function


1. Fundamental Characteristics of Functional ProgrammingFundamental Characteristics of Functional ProgrammingFundamental Characteristics of Functional ProgrammingFundamental Characteristics of Functional Programming

� TypeTypeTypeType of Functional Languagesof Functional Languagesof Functional Languagesof Functional Languages

� MostMostMostMost of them are interpreted interpreted interpreted interpreted languages

� Some of them have compiledcompiledcompiledcompiled versions

� Memory managementMemory managementMemory managementMemory management

� Implicit memory managementImplicit memory managementImplicit memory managementImplicit memory management:

11

� Implicit memory managementImplicit memory managementImplicit memory managementImplicit memory management:

� Memory management is a task of the interpreter.

� The programmer must notnotnotnot worry about memory management.

� Garbage collectionGarbage collectionGarbage collectionGarbage collection: task of the interpreter.

In shortIn shortIn shortIn short: the programmer must only worry about the Problem descriptionProblem descriptionProblem descriptionProblem description



1. Fundamental Characteristics of Functional Programming

2. Historic Summary of SchemeHistoric Summary of SchemeHistoric Summary of SchemeHistoric Summary of Scheme

12




� LISP

� Compilation versus Interpretation

� Lexical (or static) versus dynamical scope

� Origin of Scheme

13



� LISPLISPLISPLISP




14




� John McCarthyJohn McCarthyJohn McCarthyJohn McCarthy (MIT)

� “Advice Taker”“Advice Taker”“Advice Taker”“Advice Taker” program:

� Theoretical basis: Logic Mathematics

15

� Objective: Deduction and Inferences

� LISPLISPLISPLISP: LISLISLISLISt PPPProcessing (1956 – 1958)

� Second historic language of Artificial IntelligenceArtificial IntelligenceArtificial IntelligenceArtificial Intelligence (after IPL)

� At present time, second historic language in usein usein usein use (after Fortran)

� LISP is based on Lambda Calculus (Alonzo ChurchAlonzo ChurchAlonzo ChurchAlonzo Church)

� SchemeSchemeSchemeScheme is a dialectdialectdialectdialect of LISPLISPLISPLISP




� Functional Programming Characteristics Functional Programming Characteristics Functional Programming Characteristics Functional Programming Characteristics

� RecursionRecursionRecursionRecursion

� ListsListsListsLists

16

� ImplicitImplicitImplicitImplicit memory management

� Interactive and interpretedinterpretedinterpretedinterpreted programs

� SymbolicSymbolicSymbolicSymbolic Programming

� DynamicallyDynamicallyDynamicallyDynamically scopedscopedscopedscoped for nonnonnonnon local variables




� LISP’s contributionscontributionscontributionscontributions:

� Built Built Built Built –––– inininin functions

� Garbage collectionGarbage collectionGarbage collectionGarbage collection

17

� Definition Formal LanguageDefinition Formal LanguageDefinition Formal LanguageDefinition Formal Language: LISPLISPLISPLISP itselfitselfitselfitself




� ApplicationsApplicationsApplicationsApplications: Artificial IntelligenceArtificial IntelligenceArtificial IntelligenceArtificial Intelligence Programs

� Theorem verification and testing

� Symbolic differentiation and integration

� Search Problems

18

� Search Problems

� Natural Language Processing

� Computer Vision

� Robotics

� Knowledge Representation Systems

� Expert Systems

� And so on




� Dialects (1 /2)Dialects (1 /2)Dialects (1 /2)Dialects (1 /2)

� Mac LISPMac LISPMac LISPMac LISP (Man and computer or Machine – aided cognition): EastEastEastEast Coast Version

� Inter LISPInter LISPInter LISPInter LISP (Interactive LISP): WestWestWestWest Coast Version

19

� Inter LISPInter LISPInter LISPInter LISP (Interactive LISP): WestWestWestWest Coast Version

- Bolt, Beranek y Newman Company (BBN)

- Research Center of Xerox at Palo Alto (Texas)

- LISP MachineLISP MachineLISP MachineLISP Machine




� DialectsDialectsDialectsDialects (2 / 2)

� Mac LISPMac LISPMac LISPMac LISP (Man and computer or Machine – aided cognition): East Coast Version

- C-LISP: Massachusetts University

20

- C-LISP: Massachusetts University

- Franz LISP: California University (Berkeley). Compiled Compiled Compiled Compiled versionversionversionversion.

- NIL (New implementation of LISP): MIT.

- PSL (Portable Standard LISP): Utah University

- SchemeSchemeSchemeScheme: MIT.

- T (True):Yale University.

- Common LISP



� LISP

� Compilation versus InterpretationCompilation versus InterpretationCompilation versus InterpretationCompilation versus Interpretation



21



� Compilation Compilation Compilation Compilation versusversusversusversus interpretationinterpretationinterpretationinterpretation

� CompilationCompilationCompilationCompilation:

� The source code source code source code source code (high levelhigh levelhigh levelhigh level) is transformedtransformedtransformedtransformed into executable executable executable executable code code code code (low levellow levellow levellow level), which can be independently run.

22




� CompilationCompilationCompilationCompilation

23

Source codeSource codeSource codeSource codeSource codeSource codeSource codeSource code�� CompilerCompilerCompilerCompilerCompilerCompilerCompilerCompiler





24

Compilation errorsCompilation errorsCompilation errorsCompilation errorsCompilation errorsCompilation errorsCompilation errorsCompilation errors

��

Source codeSource codeSource codeSource codeSource codeSource codeSource codeSource code�� CompilerCompilerCompilerCompilerCompilerCompilerCompilerCompiler





25

Source codeSource codeSource codeSource codeSource codeSource codeSource codeSource code�� CompilerCompilerCompilerCompilerCompilerCompilerCompilerCompiler �� Executable codeExecutable codeExecutable codeExecutable codeExecutable codeExecutable codeExecutable codeExecutable code


��

Input dataInput dataInput dataInput dataInput dataInput dataInput dataInput data




26


��


��





27

Execution errorsExecution errorsExecution errorsExecution errorsExecution errorsExecution errorsExecution errorsExecution errors


��

OutputOutputOutputOutputOutputOutputOutputOutput

��


��





28


��


��




� InterpretationInterpretationInterpretationInterpretation

29



� Compilation Compilation Compilation Compilation versusversusversusversus interpretation interpretation interpretation interpretation

� Interpretation Interpretation Interpretation Interpretation or simulationsimulationsimulationsimulation: consists of a cycle of three stages

30




� Interpretation Interpretation Interpretation Interpretation or simulation: consists of a cycle of three stages

1. AnalysisAnalysisAnalysisAnalysis: the source code is analysed to determine the following correct sentence to be run.

31






2. GenerationGenerationGenerationGeneration: the sentence is transformed into executable

32

2. GenerationGenerationGenerationGeneration: the sentence is transformed into executable code.






2. GenerationGenerationGenerationGeneration: the sentence is transformed into executable

33

2. GenerationGenerationGenerationGeneration: the sentence is transformed into executable code.

3. ExecutionExecutionExecutionExecution: the executable code is run.





34

Source codeSource codeSource codeSource codeSource codeSource codeSource codeSource code�� InterpreterInterpreterInterpreterInterpreterInterpreterInterpreterInterpreterInterpreter


Input dataInput dataInput dataInput dataInput dataInput dataInput dataInput data Interpretation errorsInterpretation errorsInterpretation errorsInterpretation errorsInterpretation errorsInterpretation errorsInterpretation errorsInterpretation errors




35


��

Input dataInput dataInput dataInput dataInput dataInput dataInput dataInput data Interpretation errorsInterpretation errorsInterpretation errorsInterpretation errorsInterpretation errorsInterpretation errorsInterpretation errorsInterpretation errors






36



��


Execution errorsExecution errorsExecution errorsExecution errorsExecution errorsExecution errorsExecution errorsExecution errors






37



��




- IndependentIndependentIndependentIndependent

- Memory necessitiesMemory necessitiesMemory necessitiesMemory necessities


- DependentDependentDependentDependent

- No memory necessitiesNo memory necessitiesNo memory necessitiesNo memory necessities



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- EfficientEfficientEfficientEfficient

- GlobalGlobalGlobalGlobal

- No interactionNo interactionNo interactionNo interaction

- ClosedClosedClosedClosed code during executioncode during executioncode during executioncode during execution

- Less efficientLess efficientLess efficientLess efficient

- LocalLocalLocalLocal

- InteractionInteractionInteractionInteraction

- OpenOpenOpenOpen code during executioncode during executioncode during executioncode during execution



� LISP


� Lexical (or static) versus dynamical scopeLexical (or static) versus dynamical scopeLexical (or static) versus dynamical scopeLexical (or static) versus dynamical scope


39




� The scope rulesscope rulesscope rulesscope rules determine the declarationdeclarationdeclarationdeclaration of nonnonnonnon local identifiers

� Non Non Non Non local identifiers:

� VariablesVariablesVariablesVariables or functionsfunctionsfunctionsfunctions which can be usedusedusedused in a function or procedure but are notnotnotnot declared in that function or procedure

40

� Two typesTwo typesTwo typesTwo types

� Lexical or static scopeLexical or static scopeLexical or static scopeLexical or static scope

- WithWithWithWith “blocks structure”: Pascal, SchemeSchemeSchemeScheme

- WithoutWithoutWithoutWithout “blocks structure”: C, Fortran

� Dynamical scope:Dynamical scope:Dynamical scope:Dynamical scope:

- Always withAlways withAlways withAlways with “blocks structure”: Lisp, SNOBOL, APL




� Block structureBlock structureBlock structureBlock structure

� A procedure or function can callcallcallcall

- Itself

- Its children (but notnotnotnot its grandchildren…)

- Its brothers (but notnotnotnot its nephews)

41

- Its brothers (but notnotnotnot its nephews)

- Its father, grandfather, great-grandfather, …

- The brothers of its father, grandfather, …

� A procedure or function can be calledbe calledbe calledbe called by

- Itself

- Its father (but notnotnotnot by its grandfather, …)

- Its children, grandchildren, great-grandchildren, …

- Its brothers and their children, grandchildren, ...


P

Declaration of procedure f

Declaration of procedure g

Declaration of procedure h

Declaration of procedure k

Example of Example of Example of Example of blocks structureblocks structureblocks structureblocks structure

42

Declaration of procedure l

Declaration of procedure m

Declaration of procedure n


P

f l

43

m ng h

k Hierarchical blocks structureHierarchical blocks structureHierarchical blocks structureHierarchical blocks structure


f l

P

44

m ng h

k Functions which can be called by ffff


f l

P

45

m ng h

k Functions which can call f


f l

P

46

m ng h

k Functions which can be called by h


f l

P

47

m ng h

k Functions which can call h




� LexicalLexicalLexicalLexical or static scopeor static scopeor static scopeor static scope

� The declarationdeclarationdeclarationdeclaration of a nonnonnonnon local identifier depends on the closest closest closest closest lexical context: lexical context: lexical context: lexical context:

You only have to readreadreadread the program

48

to determine the declaration of an identifier.

� The closest nesting rules:The closest nesting rules:The closest nesting rules:The closest nesting rules:

- The scopescopescopescope of a procedure (****) ffff includes the procedure ffff.

- If a nonnonnonnon local identifier xxxx is used in f f f f then the declaration of xxxx must be found in the closestclosestclosestclosest procedure gggg which includes ffff

- NoticeNoticeNoticeNotice (****) : procedure, function or block


Example: Example: Example: Example:

Lexical scope Lexical scope Lexical scope Lexical scope

withwithwithwith “block structure”“block structure”“block structure”“block structure”

Declaration of procedure hDeclaration of variable x (x1)Declaration of variable y (y1)Declaration of variable z (z1)

Declaration of procedure gDeclaration of variable x (x2) Declaration of variable y (y2)

Declaration of procedure fDeclaration of variable x (x3)

49

withwithwithwith “block structure”“block structure”“block structure”“block structure”Use of x (�� x3)Use of y (�� y2)Use of z (�� z1)

Use of x (�� x2)Use of y (�� y2)Use of z (�� z1)Call to f

Use of x (�� x1)Use of y (�� y1)Use of z (�� z1)Call to g




� LexicalLexicalLexicalLexical or static scopeor static scopeor static scopeor static scope

� WithoutWithoutWithoutWithout block structure:

- If xxxx is notnotnotnot local for a specificspecificspecificspecific function then it is notnotnotnot local for allallallall functions

50


int x; /* x1 */int y; /* y1 */int z; /* z1 */

main(){

int x; /* x2 */int y; /* y2 */

/* Use of x �� x2 *//* Use of y �� y2 */

Example in C:Example in C:Example in C:Example in C:

Global variablesGlobal variablesGlobal variablesGlobal variables arearearearenot not not not recommendedrecommendedrecommendedrecommended

51

/* Use of y �� y2 *//* Use of z �� z1 *//* Call to f */f ();

}

f(){int x; /* x3 *//* Use of x �� x3 *//* Use of y �� y1 *//* Use of z �� z1 */}

withoutwithoutwithoutwithout

“block structure”“block structure”“block structure”“block structure”




� DynamicalDynamicalDynamicalDynamical scope:scope:scope:scope:

� The declarationdeclarationdeclarationdeclaration of an identifieridentifieridentifieridentifier depends on the execution of the execution of the execution of the execution of the programprogramprogramprogram

You have to runrunrunrun the program

52

You have to runrunrunrun the program

to determine the declaration of an identifier

� The closest activation rules:The closest activation rules:The closest activation rules:The closest activation rules:

- The scopescopescopescope of a procedure (****) ffff includes the procedure ffff.

- If a nonnonnonnon local identifier xxxx is used in the activationactivationactivationactivation of f f f f then the declaration of xxxx must be found in the closestclosestclosestclosest activeactiveactiveactiveprocedure gggg with a declaration of x

- NoticeNoticeNoticeNotice (****) : procedure, function or block





� The dynamical scopedynamical scopedynamical scopedynamical scope allows that an identifieridentifieridentifieridentifier can be associated to different declarationsdifferent declarationsdifferent declarationsdifferent declarations during the program execution

53


ProgramDeclaration of variable x

Declaration of procedure fUse of x

Declaration of procedure gDeclaration of variable x


Example:Example:Example:Example:

LexicalLexicalLexicalLexical

versus versus versus versus

54

Declaration of procedure hUse of xCall to f

Call to fCall to hif condition = true then Call to gelse Use of x

Use of xCall to fCall to g

DynamicalDynamicalDynamicalDynamical

scopescopescopescope


Program

f g

55

f

f

h

Activation StackActivation StackActivation StackActivation Stack Activation TreeActivation TreeActivation TreeActivation Tree


Program

f g

56

f

f

h

Activation StackActivation StackActivation StackActivation Stack

Program

Activation TreeActivation TreeActivation TreeActivation Tree


Program

f g

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f

f

h


Program


f


Program

f g

58

f

f

h


Program



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f

f

h


Program

g


Program

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f

f

h


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g

f


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f

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h


Program


g


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h


Program

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h


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f

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f

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h


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h

f


Program

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f

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f

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g


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f

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g

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h

Changes in the activation Stack (1 / 2)Changes in the activation Stack (1 / 2)Changes in the activation Stack (1 / 2)Changes in the activation Stack (1 / 2)

f

g

Program

h


f

g

Program

h

g

Program

hg

Program

69Changes in the activation Stack (2 / 2)Changes in the activation Stack (2 / 2)Changes in the activation Stack (2 / 2)Changes in the activation Stack (2 / 2)

Program


ProgramDeclaration of variable x (x1)


Declaration of procedure gDeclaration of variable x (x2)


Run with Run with Run with Run with

lexicallexicallexicallexical scopescopescopescope

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Program

f g

Lexical scopeLexical scopeLexical scopeLexical scope

71

f

f

h









72



Use of x1Call to fCall to g



Program

f g

Lexical scopeLexical scopeLexical scopeLexical scope� Use of Use of Use of Use of x1x1x1x1 of of of of ProgramProgramProgramProgram in in in in ProgramProgramProgramProgram

73

f

f

h


Program









74







Declaration of procedure fUse of x1





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Program

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Lexical scopeLexical scopeLexical scopeLexical scope� Use of Use of Use of Use of x1x1x1x1 of of of of ProgramProgramProgramProgram in in in in ffff

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Declaration of procedure hUse of x2Call to f





Program

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Lexical scopeLexical scopeLexical scopeLexical scope� Use of Use of Use of Use of x2x2x2x2 of of of of gggg in in in in hhhh

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Call to fCall to hif condition = true then Call to gelse Use of x2




Program

f g

Lexical scopeLexical scopeLexical scopeLexical scope� Use of Use of Use of Use of x2x2x2x2 of of of of gggg in in in in gggg

92

f

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f

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dynamicaldynamicaldynamicaldynamical scopescopescopescope

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Program

f g

Dynamical scopeDynamical scopeDynamical scopeDynamical scope

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f

f

h









98



Use of x1Call to fCall to g



Program

f g

Dynamical scopeDynamical scopeDynamical scopeDynamical scope� Use of Use of Use of Use of x1x1x1x1 of of of of ProgramProgramProgramProgram in in in in ProgramProgramProgramProgram

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f

f

h


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f g

Dynamical scopeDynamical scopeDynamical scopeDynamical scope� Use of Use of Use of Use of x1x1x1x1 of of of of ProgramProgramProgramProgram in in in in ffff

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h


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f


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f g


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f

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f g

Dynamical scopeDynamical scopeDynamical scopeDynamical scope� NoticeNoticeNoticeNotice: use of : use of : use of : use of x2x2x2x2 of of of of gggg in in in in ffff

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f

f

h


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g

f


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f

f

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g








110












111

Declaration of procedure hUse of x2Call to f





Program

f g

Dynamical scopeDynamical scopeDynamical scopeDynamical scope� Use of Use of Use of Use of x2x2x2x2 of of of of gggg in in in in hhhh

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f

f

h


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g

h








113












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Program

f g

f

Dynamical scopeDynamical scopeDynamical scopeDynamical scope� NoticeNoticeNoticeNotice: use of : use of : use of : use of x2x2x2x2 of of of of gggg in in in in ffff

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f

f

h


Program

g

h

f


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f g


116

f

f

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Program

f g

Dynamical scopeDynamical scopeDynamical scopeDynamical scope� Use of Use of Use of Use of x2x2x2x2 of of of of gggg in in in in gggg

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f

f

h


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g








119






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f g


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f

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Program

f g


121

f

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� LISP


� Dynamically versus statically scope

� Origin of SchemeOrigin of SchemeOrigin of SchemeOrigin of Scheme

122



� Origin of SchemeOrigin of SchemeOrigin of SchemeOrigin of Scheme:

� Gerald Jay SussmanSussmanSussmanSussman (MIT) and Guy Lewis SteeleSteeleSteeleSteele Jr.

� QuestionQuestionQuestionQuestion:

How would LISPLISPLISPLISP be with lexicallexicallexicallexical or static static static static scopescopescopescope rules?

� AnswerAnswerAnswerAnswer: new language � SchemeSchemeSchemeScheme

123

� AnswerAnswerAnswerAnswer: new language � SchemeSchemeSchemeScheme

� More efficientefficientefficientefficient implementation of recursionrecursionrecursionrecursion

� First class functionsFirst class functionsFirst class functionsFirst class functions.

� Rigorous semanticsemanticsemanticsemantic rules

� InfluenceInfluenceInfluenceInfluence on Common LISP: lexical scope rules

� Revised Revised Revised Revised 5555 Report on the Algorithmic Language SchemeReport on the Algorithmic Language SchemeReport on the Algorithmic Language SchemeReport on the Algorithmic Language Scheme



� SchemeSchemeSchemeScheme:

� Structure of scheme programsStructure of scheme programsStructure of scheme programsStructure of scheme programs

� Sequence of

- definitionsdefinitionsdefinitionsdefinitions of functions and variables

- and expressionsexpressionsexpressionsexpressions

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- and expressionsexpressionsexpressionsexpressions

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ARTIFICIAL INTELLIGENCE ARTIFICIAL INTELLIGENCE ARTIFICIAL INTELLIGENCE ARTIFICIAL INTELLIGENCE ARTIFICIAL INTELLIGENCE ARTIFICIAL INTELLIGENCE ARTIFICIAL INTELLIGENCE ARTIFICIAL INTELLIGENCE LANGUAGESLANGUAGESLANGUAGESLANGUAGESLANGUAGESLANGUAGESLANGUAGESLANGUAGES

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TECHNICAL ENGINEERING IN SYSTEMS COMPUTER SCIENCETECHNICAL ENGINEERING IN SYSTEMS COMPUTER SCIENCETECHNICAL ENGINEERING IN SYSTEMS COMPUTER SCIENCETECHNICAL ENGINEERING IN SYSTEMS COMPUTER SCIENCE

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ARTIFICIAL INTELLIGENCE LANGUAGES · Artificial Intelligence Languages Subject 1.Subject...

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