Essentials of Programming Languages, 3rd Edition

433 Pages·2008·3.41 MB·english

by  Daniel P. Friedman

computer science/programming languages PE
RS
Essentials of Programming Languages OS
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third edition G
N ESSENTIALS OF
Daniel P. Friedman and Mitchell Wand
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This book provides students with a deep, working understanding of the essential concepts of program- I
MA
ming languages. Most of these essentials relate to the semantics, or meaning, of program elements,
L PROGRAMMING
and the text uses interpreters (short programs that directly analyze an abstract representation of the M
S THIRD EDITION
program text) to express the semantics of many essential language elements in a way that is both clear

IO
and executable. The approach is both analytical and hands-on. The book provides views of program- N
ming languages using widely varying levels of abstraction, maintaining a clear connection between the F
G LANGUAGES
high-level and low-level views. Exercises are a vital part of the text and are scattered throughout; the text

explains the key concepts, and the exercises explore alternative designs and other issues. The complete L
Scheme code for all the interpreters and analyzers in the book can be found online through The MIT A
Press website. N
For this new edition, each chapter has been revised and many new exercises have been added.
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Significant additions have been made to the text, including completely new chapters on modules and
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continuation-passing style. Essentials of Programming Languages can be used for both graduate and un-
dergraduate courses, and for continuing education courses for programmers. A
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Daniel P. Friedman is Professor of Computer Science at Indiana University and is the author of many E
books published by The MIT Press, including The Little Schemer (fourth edition, 1995), The Seasoned S
Schemer (1995), A Little Java, A Few Patterns (1997), each of these coauthored with Matthias Felleisen,
and The Reasoned Schemer (2005), coauthored with William E. Byrd and Oleg Kiselyov. Mitchell Wand is
Professor of Computer Science at Northeastern University. T
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“With lucid prose and elegant code, this book provides the most concrete introduction to the few build- D D
ing blocks that give rise to a wide variety of programming languages. I recommend it to my students and A
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look forward to using it in my courses.” D I
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—Chung-chieh Shan, Department of Computer Science, Rutgers University TI 9
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“Having taught from EOPL for several years, I appreciate the way it produces students who understand 7
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the terminology and concepts of programming languages in a deep way, not just from reading about the 3
concepts, but from programming them and experimenting with them. This new edition has an increased /2
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emphasis on types as contracts for defining procedure interfaces, which is quite important for many r /0
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students.” e C
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—Gary T. Leavens, School of Electrical Engineering and Computer Science, University of Central Florida m A
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“I’ve found the interpreters-based approach for teaching programming languages to be both compelling n A
and rewarding for my students. Exposing students to the revelation that an interpreter for a program- a G
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ming language is itself just another program opens up a world of possibilities for problem solving. The d E
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third edition of Essentials of Programming Languages makes this approach of writing interpreters more W O
accessible than ever.” B
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—Marc L. Smith, Department of Computer Science, Vassar College n A
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978-0-262-06279-4 Daniel P. Friedman and Mitchell Wand
The MIT Press
Massachusetts Institute of Technology
Cambridge, Massachusetts 02142
http://mitpress.mit.edu
Essentials of
Programming
Languages
third edition

Essentials of
Programming
Languages
third edition
Daniel P. Friedman
Mitchell Wand
TheMITPress
Cambridge,Massachusetts
London,England
©2008DanielP.FriedmanandMitchellWand
All rights reserved. No part of this book may be reproduced in any form by any
electronicormechanicalmeans(includingphotocopying,recording,orinformation
storageandretrieval)withoutpermissioninwritingfromthepublisher.
MITPressbooksmaybepurchasedatspecialquantitydiscountsforbusinessorsales
promotional use. For information, please email [email protected]
write to Special Sales Department, The MIT Press, 55 Hayward Street, Cambridge,
MA02142.
ThisbookwassetinLATEX2εbytheauthors,andwasprintedandboundintheUnited
StatesofAmerica.
LibraryofCongressCataloging-in-PublicationData
Friedman,DanielP.
Essentialsofprogramminglanguages/DanielP.Friedman,Mitchell
Wand.
—3rded.
p. cm.
Includesbibliographicalreferencesandindex.
ISBN978-0-262-06279-4 (hbk.:alk.paper)
1.ProgrammingLanguages(Electroniccomputers).I.Wand,
Mitchell.II.Title.
QA76.7.F73 2008
005.1—dc22 2007039723
10987654321
Contents
ForewordbyHalAbelson ix
Preface xv
Acknowledgments xxi
1 InductiveSetsofData 1
1.1RecursivelySpecifiedData 1
1.2DerivingRecursivePrograms 12
1.3AuxiliaryProceduresandContextArguments 22
1.4Exercises 25
2 DataAbstraction 31
2.1SpecifyingDataviaInterfaces 31
2.2RepresentationStrategiesforDataTypes 35
2.3InterfacesforRecursiveDataTypes 42
2.4AToolforDefiningRecursiveDataTypes 45
2.5AbstractSyntaxandItsRepresentation 51
3 Expressions 57
3.1SpecificationandImplementationStrategy 57
3.2LET:ASimpleLanguage 60
3.3PROC:ALanguagewithProcedures 74
3.4LETREC:ALanguagewithRecursiveProcedures 82
3.5ScopingandBindingofVariables 87
3.6EliminatingVariableNames 91
3.7ImplementingLexicalAddressing 93
vi Contents
4 State 103
4.1ComputationalEffects 103
4.2EXPLICIT-REFS:ALanguagewithExplicitReferences 104
4.3IMPLICIT-REFS:ALanguagewithImplicitReferences 113
4.4MUTABLE-PAIRS:ALanguagewithMutablePairs 124
4.5Parameter-PassingVariations 130
5 Continuation-PassingInterpreters 139
5.1AContinuation-PassingInterpreter 141
5.2ATrampolinedInterpreter 155
5.3AnImperativeInterpreter 160
5.4Exceptions 171
5.5Threads 179
6 Continuation-PassingStyle 193
6.1WritingProgramsinContinuation-PassingStyle 193
6.2TailForm 203
6.3ConvertingtoContinuation-PassingStyle 212
6.4ModelingComputationalEffects 226
7 Types 233
7.1ValuesandTheirTypes 235
7.2AssigningaTypetoanExpression 238
7.3CHECKED:AType-CheckedLanguage 240
7.4INFERRED:ALanguagewithTypeInference 248
8 Modules 275
8.1TheSimpleModuleSystem 276
8.2ModulesThatDeclareTypes 292
8.3ModuleProcedures 311
9 ObjectsandClasses 325
9.1Object-OrientedProgramming 326
9.2Inheritance 329
9.3TheLanguage 334
9.4TheInterpreter 336
9.5ATypedLanguage 352
9.6TheTypeChecker 358
Contents vii
A ForFurtherReading 373
B TheSLLGENParsingSystem 379
B.1Scanning 379
B.2Parsing 382
B.3ScannersandParsersinSLLGEN 383
Bibliography 393
Index 401

Foreword
This book brings you face-to-face with the most fundamental idea in com-
puterprogramming:
Theinterpreter foracomputerlanguageisjustanotherprogram.
It sounds obvious, doesn’t it? But the implications are profound. If you
are a computational theorist, the interpreter idea recalls Gödel’s discovery
of the limitations of formal logical systems, Turing’s concept of a universal
computer,andvonNeumann’sbasicnotionofthestored-programmachine.
Ifyou area programmer,mastering the ideaof aninterpreterisa sourceof
greatpower. It provokes a realshift in mindset, a basic change in the way
youthinkaboutprogramming.
IdidalotofprogrammingbeforeIlearnedaboutinterpreters,andIpro-
duced some substantial programs. One of them, for example, was a large
data-entryandinformation-retrievalsystemwritteninPL/I.WhenIimple-
mented my system, I viewed PL/I as a fixed collection of rules established
bysome unapproachablegroupoflanguagedesigners. Isawmyjob asnot
tomodifytheserules,oreventounderstandthemdeeply,butrathertopick
through the (very) large manual, selecting this or that feature to use. The
notionthattherewassomeunderlyingstructuretothewaythelanguagewas
organized, and thatI might want tooverride some of the language design-
ers’decisions,neveroccurredtome. Ididn’tknowhowtocreateembedded
sublanguages to help organize my implementation, so the entire program
seemed like a large, complex mosaic, where each piece had to be carefully
shaped and fitted into place, rather than a cluster of languages, where the
piecescouldbeflexiblycombined. Ifyoudon’tunderstandinterpreters,you
canstillwriteprograms;youcanevenbeacompetentprogrammer.Butyou
can’tbeamaster.