The World of Programming Languages

372 Pages·1987·13.409 MB·

by  Michael Marcotty, Henry Ledgard (auth.)

Springer Books on Professional Computing
Edited bl,J Henn,J Ledgord
Springer Books on Professional Computing
Computer Confidence: A Human Approach to Computers
Bruce D. Sanders. viii, 90 pages. 23 figures. 1984. ISBN 0-387-90917-6
The Unix System Guidebook: An Introductory Guide for Serious Users
Peter P. Silvester. xi, 207 pages. 6 figures. 1984. ISBN 0-387-90906-0
The American Pascal Standard: With Annotations
Henry Ledgard. vii, 97 pages. 1984. ISBN 0-387-91248-7
Modula-2 for Pascal Progrflmmers
Richard Gleaves. x, 145 pages. 18 figures. 1984. ISBN 0-387-96051-1
Ada ® in Practice
Christine N. Ausnit, Norman H. Cohen, John B. Goodenough, R. Sterling Eanes.
xv, 192 pages. 79 figures. 1985. ISBN 0-387-96182-8
The World of Programming Languages
Michael Marcotty, Henry Ledgard. xvi, 360 pages. 30 figures. 1986.
ISBN 0-387-96440-1
The World of
Programming Languages
Michael Marcotty Henry ledgard
With 30 Illustrations
Springer-Verlag
New York Berlin Heidelberg
London Paris Tokyo
Michael Marcotty
Computer Science Department
General Motors Research Laboratories
Wanen, MI 48090-9055
U.S.A.
Henry Ledgard
Drummer Hill Road, RFD
Amhersl, MA 01002
U.S.A.
Series Editor
Henry Ledgard
Library of Congress Cataloging-in-Publiclllion Data
MarcoUy, Michael
The world of programming languages.
(Springer books on professional computing)
Bibliography: p.
Includes index.
I. Programming language~ (Electronic computers)
I. Ledgard, Henry F. II. Title.
Ill. Series.
QA76.7.M346 1986 005.13 86-26083
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Original te;<tbook edition, PrQgr(ll"",i"x Lt"'~""Ke Umd.• c "pt'; S),,,uu. Se",,,"';c. •.
published by Science Research Associates. Inc ..C hicago, Illinois. Copyright C 1986. 1981.
C 1987 by Science Research Associates. Inc.
All rights reserved. Trade edition reprinted by permission. This work may nOi be translated orcopicd
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ISBN -13: 978·0-387-96440-9 e-ISBN-13:978-I- 4612-4692-3
DOl: 10.1007/978-1-4612-4692-3
Preface
The earth, viewed through the window of an airplane, shows a regularity and reptition
of features, for example, hills, valleys, rivers, lakes, and forests. Nevertheless, there is
great local variation; Vermont does not look like Utah. Similarly, if we rise above the
details of a few programming languages, we can discern features that are common to
many languages. This is the programming language landscape; the main features include
variables, types, control structures, and input/output. Again, there is local variation; Pascal
does not look like Basic.
This work is a broad and comprehensive discussion of the principal features of the
major programming languages.
A Study of Concepts
The text surveys the landscape of programming languages and its features. Each chapter
concentrates on a single language concept. A simple model of the feature, expressed as
a mini-language, is presented. This allows us to study an issue in depth and relative
isolation. Each chapter concludes with a discussion of the way in which the concept is
incorporated into some well-known languages. This permits a reasonably complete coverage
of language issues.
A Study of Human Aspects
Throughout the book, we view a programming language as a notation. The user of a
notation must make a mental investment in learning before gaining any advantage. If the
investment is greater than the return in mental leverage for the production of correct
programs, the language fails. The mental leverage results from an increased ability by
the programmer to master the details of a computation. For the investment to be low,
there must be an inherent simplicity in the language with uniformly applied rules and few
special cases.
vi Preface
For good mental leverage, the language must provide powerful abstraction tools that
allow the user to subdue the clamor of complexity and master a large program. It is
essential to remember that the most important function of a programming language is to
communicate the algorithm to other programmers. It is constructed for the convenience
of humans, not of machines.
Basis on Existing Languages
The reader is expected to have experience with one (perhaps more) high-level languages.
The concepts discussed in this book are drawn mainly from Ada®, Algol 60, Algol 68,
I
Cobol, Fortran, Lisp, Pascal, and PLiI. Between these languages, almost any programming
language principle, good or bad, can be found. Other languages referenced include APL,
Basic, Bliss, Modula-2, Simula 67, and Smalltalk®.2 Obviously, there can be no attempt
to present a description of all these languages.
However, the reader, even if unfamiliar with these languages, should have no difficulty
in understanding this text. The chapters that describe particular language features each
contain a section-"Where to Look"-that describes the realization of the feature in one
or two real languages. Reference material for all languages mentioned is cited in the
bibliography under the name of the language. Suggestions for further reading are contained
at the end of each chapter.
Levels of Understanding
Although each chapter in this book is self-contained, we treat programming languages
in four successively deeper levels. The first level, Chapters I and 2, introduces the area
of programming language, discusses a number of broad issues, such as the formal de
scription of languages and compilers, and generally sets the landscape for the remainder
of the book.
The second level, Chapters 3 through 8, discusses six dominant features of most
contemporary languages: assignment, control structures, data types, input/output. pro
cedures, and nesting.
The third level. Chapters 9 through 13, treats more advanced topics. data definition.
dynamically varying data structures, applicative languages, exception handling. concUlTent
processing, and modularization.
The last chapter, Chapter 14, presents some views on the complexity of programming
languages.
The implementation of languages is not discussed specifically. However, where ap
propriate, the method of implementation is described. For example, in the chapter on
block structure, the dynamic allocation of variables is discussed. The reader is thus able
to see how language design, translation processes, and execution environment interact.
Acknowledgements
One of the first uses of mini-languages as a vehicle for describing language principles
was in Ledgard's paper, "Ten Mini-Languages: A Study for Topical Issues in Programming
I Ada is a Registered Trademark of the Ada Joint Program Office-U.S. Government.
Smalltalk is a Trademark of the Xerox Corporation.
Preface vii
Languages" [Ledgard 1971]. The book has gained much of its breadth from the work
done by Ledgard on the design of Ada. The syntax of many of the mini-languages has
also benefitted from this work.
This work is derived from a longer text edition published by Science Research As
sociates (S.R.A.) of Chicago.
Michael Marcotty
Henry Ledgard
Contents
Preface ...................................................................... v
Acknowledgements ......................................................... xiii
1. Introduction ......................................................... .
1.1 The Building of the Tower of Babel ................................... I
1.2 What Is a Programming Language? .................................... 5
1.3 Why Study Programming Languages? ................................. 10
1.4 What Should We Look for in a Language? ............................. 10
1.5 Language Design Issues .............................................. 12
1.6 The Study of Programming Languages ................................. 15
Further Reading .......................................................... 17
2. Elements of a Programming Language ................................. 19
2.1 Informal Description of Mini-language Core ........................... 20
2.2 Informal Semantics of Mini-language Core ............................. 24
2.3 Language Design and the Programming Process ......................... 30
2.4 The Definition of Programming Languages... .. ...... .. .. ...... .... .. .. 34
2.5 The Formal Description of Syntax ..................................... 40
2.6 Other Context-free Syntax Definitions ................................. 47
Further Reading .......................................................... 5 1
3. Names, Locations, and Values ......................................... 53
3.1 Mini-language Ref ................................................... 54
3.2 Declarations ......................................................... 60
3.3 Assignment .......................................................... 63
3.4 Statements as Expressions ............................................ 67
3.5 Where to Look: Algol 68, Smalltalk ............................... 69
Further Reading .......................................................... 71
x Contents
4. Control Structures .................................................... 73
4. I Mini-language Control ............................................... 73
4.2 Basic Control Structures and Flowgraphs .............................. 79
4.3 Theorems on Control Structures ....................................... 87
4.4 Other One-in, One-out Control Structures .............................. 91
4.5 The Goto Statement and Label Values ................................. 95
4.6 Conclusions ......................................................... 97
4.7 Where to Look: Pasoal, Ada ........................................ 104
Further Reading 106
s. Data Types ........................................................... 109
5. I Mini-language Type.................................................. 109
5.2 The Meaning of Type ................................................ 114
5.3 Primitive Types ...................................................... 116
5.4 Array Types ......................................................... 123
5.5 Record Types ........................................................ 126
5.6 Type Checking ...................................................... 132
5.7 Where to Look: Fortran, PLII ...................................... 133
Further Reading .......................................................... 134
6. Input and Output ..................................................... 137
6.1 Mini-language Format ................................................ 138
6.2 Varieties of Input-output Specifications ................................ 142
6.3 Communication with the Outside World ............................... 154
6.4 Where to Look: Fortran, Cobol, Ada ............................... 157
Further Reading .......................................................... 159
7. Procedures and Parameters 161
7. I Mini-language Procedures 162
7.2 Procedures as Abstractions 170
7.3 Arguments and Parameters ............................................ 172
7.4 Value-returning Procedures ........................................... 178
7.5 Coroutines .......................................................... 179
7.6 Where to Look: PLII, Ada ........................................... 183
Further Reading .......................................................... 184
8. Nesting and Scope ..................................................... 187
8.1 Mini-language Scope ................................................. 187
8.2 The Idea of Scope ................................................... 194
8.3 Storage Allocation ................................................... 198
8.4 Dynamic Scope ...................................................... 204
8.5 Where to Look: Pascal, PLlI, APL .................................. 206
Further Reading .......................................................... 209
9. Definition of New Data Types ......................................... 21 I
9. I Mini-language Typedef ............................................... 212
9.2 Type Definitions ..................................................... 221
9.3 Definition of Structured Types ........................................ 224
9.4 User Defined Operators .............................................. 228
9.5 Where to Look: Pascal, Algol68 ................................... 230
Further Reading .......................................................... 233
Contents xi
10. Dynamically Varying Structures ....................................... 235
10.1 Mini-language Structures ............................................ 235
10.2 Dynamically Varying Data Structures ................................. 243
10.3 Pointers ............................................................ 245
10.4 Design Criteria for Data Structures ................................... 246
10.5 Dynamic Allocation of Storage ...................................... 249
10.6 Where to Look: PLII, Pascal, Ada ................................. 251
Further Reading .......................................................... 253
11. Exception Handling ................................................... 255
11.1 Mini-language Exceptions ........................ , . . . . . . . . . . . . . . . . .. 256
11.2 Exceptions ......................................................... 260
11.3 Issues in Exception Handling ........................................ 262
11.4 Where to Look: PL/I, Ada ......................................... 266
Further Reading .......................................................... 269
12. Parallel Processing .................................................... 271
12.1 Mini-language Parallel .............................................. 272
12.2 A First Solution to the Decoding Problem ............................ 277
12.3 Putting a Buffer in a Task ........................................... 279
12.4 Interrupting ........................................................ 281
12.5 Issues in Parallel Processing ......................................... 284
12.6 Where to Look: Concurrent Pascal, Modula-2, Ada .............. 289
Further Reading .......................................................... 291
13. Separately Compiled Modules ......................................... 293
13.1 Mini-language Modules ............................................. 295
13.2 Packaging Subprograms ............................................. 299
13.3 Abstract Data Types ................................................ 303
13.4 Where to Look: PLlI, Modula 2, Ada, Smalltalk ................. 305
Further Reading .......................................................... 31 I
14. The Swamp of Complexity ............................................ 313
14.1 The Forms of Complexity ........................................... 313
14.2 Escaping from the Swamp ........................................... 319
References 323
Index 347