Common LISP. The Language. Second Edition

1096 Pages·1990·2.629 MB·

by  Guy Steele

Contents
Preface (Second Edition) xi 2.3. Symbols 29
2.4. Lists and Conses 32
Acknowledgments (Second Edition)
2.5. Arrays 33
xiii
2.5.1. Vectors 35
Acknowledgments(FirstEdition) xvii 2.5.2. Strings 36
2.5.3. Bit-Vectors 37
1. Introduction 1 2.6. Hash Tables 38
2.7. Readtables 38
1.1. Purpose 1
2.8. Packages 38
1.2. Notational Conventions 4
2.9. Pathnames 38
1.2.1. Decimal Numbers 4
2.10. Streams 38
1.2.2. Nil, False, and the Empty
2.11. Random-States 39
List 4
2.12. Structures 39
1.2.3. Evaluation, Expansion, and
2.13. Functions 39
Equivalence 5
2.14. Unreadable Data Objects 40
1.2.4. Errors 5
2.15. Overlap, Inclusion, and
1.2.5. Descriptions of Functions and
Disjointness of Types 41
Other Entities 6
1.2.6. The Lisp Reader 10
1.2.7. Overview of Syntax 10 3. Scope and Extent 46
2. Data Types 13
4. Type Specifiers 53
2.1. Numbers 16
2.1.1. Integers 17 4.1. Type Speci(cid:12)er Symbols 53
2.1.2. Ratios 19 4.2. Type Speci(cid:12)er Lists 53
2.1.3. Floating-Point Numbers 20 4.3. Predicating Type
2.1.4. Complex Numbers 24 Speci(cid:12)ers 55
2.2. Characters 24 4.4. Type Speci(cid:12)ers That
2.2.1. Standard Characters 25 Combine 55
2.2.2. Line Divisions 26 4.5. Type Speci(cid:12)ers That
2.2.3. Non-standard Characters 27 Specialize 57
2.2.4. Character Attributes 28 4.6. Type Speci(cid:12)ers That
2.2.5. String Characters 28 Abbreviate 64
v
vi CONTENTS
4.7. De(cid:12)ning New Type 7.8. Iteration 172
Speci(cid:12)ers 66 7.8.1. Inde(cid:12)nite Iteration 172
4.8. Type Conversion Function 68 7.8.2. General Iteration 173
4.9. Determining the Type of an 7.8.3. Simple Iteration
Object 70 Constructs 178
4.10. Type Upgrading 72 7.8.4. Mapping 180
7.8.5. The \Program Feature" 183
5. Program Structure 73 7.9. Structure Traversal and Side
Effects 188
5.1. Forms 73
7.10. Multiple Values 189
5.1.1. Self-Evaluating Forms 74
7.10.1. Constructs for Handling
5.1.2. Variables 74
Multiple Values 190
5.1.3. Special Forms 76
7.10.2. Rules Governing the Passing of
5.1.4. Macros 78
Multiple Values 195
5.1.5. Function Calls 79
7.11. Dynamic Non-Local Exits 198
5.2. Functions 79
5.2.1. Named Functions 80
5.2.2. Lambda-Expressions 80 8. Macros 205
5.3. Top-Level Forms 88 8.1. Macro De(cid:12)nition 206
5.3.1. De(cid:12)ning Named Functions 90 8.2. Macro Expansion 215
5.3.2. Declaring Global Variables and 8.3. Destructuring 217
Named Constants 92 8.4. Compiler Macros 217
5.3.3. Control of Time of 8.5. Environments 220
Evaluation 94
9. Declarations 228
6. Predicates 101
9.1. Declaration Syntax 228
6.1. Logical Values 102 9.2. Declaration Speci(cid:12)ers 237
6.2. Data Type Predicates 102 9.3. Type Declaration for
6.2.1. General Type Predicates 102 Forms 252
6.2.2. Speci(cid:12)c Data Type
Predicates 105
10. Symbols 254
6.3. Equality Predicates 110
6.4. Logical Operators 116 10.1. The Property List 254
10.2. The Print Name 259
7. Control Structure 119 10.3. Creating Symbols 260
7.1. Constants and Variables 120
11. Packages 264
7.1.1. Reference 120
7.1.2. Assignment 127 11.1. Consistency Rules 266
7.2. Generalized Variables 129 11.2. Package Names 266
7.3. Function Invocation 154 11.3. Translating Strings to
7.4. Simple Sequencing 155 Symbols 268
7.5. Establishing New Variable 11.4. Exporting and Importing
Bindings 157 Symbols 270
7.6. Conditionals 165 11.5. Name Con(cid:13)icts 272
7.7. Blocks and Exits 170 11.6. Built-in Packages 275
CONTENTS vii
11.7. Package System Functions and 14.2. Concatenating, Mapping, and
Variables 279 Reducing Sequences 421
11.8. Modules 295 14.3. Modifying Sequences 426
11.9. An Example 296 14.4. Searching Sequences for
Items 432
14.5. Sorting and Merging 436
12. Numbers 307
12.1. Precision, Contagion, and
15. Lists 440
Coercion 308
12.2. Predicates on Numbers 312 15.1. Conses 440
12.3. Comparisons on Numbers 313 15.2. Lists 442
12.4. Arithmetic Operations 315 15.3. Alteration of List
12.5. Irrational and Transcendental Structure 453
Functions 319 15.4. Substitution of
12.5.1. Exponential and Logarithmic Expressions 455
Functions 320 15.5. Using Lists as Sets 457
12.5.2. Trigonometric and Related 15.6. Association Lists 463
Functions 323
12.5.3. Branch Cuts, Principal Values,
16. Hash Tables 468
and Boundary Conditions in
the Complex Plane 332 16.1. Hash Table Functions 469
12.6. Type Conversions and 16.2. Primitive Hash Function 475
Component Extractions on
Numbers 375
17. Arrays 476
12.7. Logical Operations on
Numbers 382 17.1. Array Creation 476
12.8. Byte Manipulation 17.2. Array Access 481
Functions 388 17.3. Array Information 482
12.9. Random Numbers 391 17.4. Functions on Arrays of
12.10. Implementation Bits 487
Parameters 394 17.5. Fill Pointers 489
17.6. Changing the Dimensions of an
Array 490
13. Characters 398
13.1. Character Attributes 401
18. Strings 495
13.2. Predicates on Characters 403
13.3. Character Construction and 18.1. String Access 496
Selection 409 18.2. String Comparison 496
13.4. Character Conversions 410 18.3. String Construction and
13.5. Character Control-Bit Manipulation 499
Functions 413
19. Structures 504
14. Sequences 415
19.1. Introduction to
14.1. Simple Sequence Structures 504
Functions 419 19.2. How to Use Defstruct 506
viii CONTENTS
19.3. Using the Automatically 22.3.1. Output to Character
De(cid:12)ned Constructor Streams 623
Function 510 22.3.2. Output to Binary
19.4. Defstruct Slot-Options 512 Streams 627
19.5. Defstruct Options 513 22.3.3. Formatted Output to
19.6. By-Position Constructor Character Streams 627
Functions 519 22.4. Querying the User 659
19.7. Structures of Explicitly
Speci(cid:12)ed Representational 23. File System Interface 661
Type 523
23.1. File Names 661
19.7.1. Unnamed Structures 523
23.1.1. Pathnames 662
19.7.2. Named Structures 524
23.1.2. Case Conventions 668
19.7.3. Other Aspects of Explicitly
23.1.3. Structured Directories 672
Speci(cid:12)ed Structures 526
23.1.4. Extended Wildcards 675
23.1.5. Logical Pathnames 681
20. The Evaluator 528
23.1.5.1. Syntax of Logical Pathname
20.1. Run-Time Evaluation of Namestrings 681
Forms 528 23.1.5.2. Parsing of Logical Pathname
20.2. The Top-Level Loop 532 Namestrings 682
23.1.5.3. Using Logical
21. Streams 535 Pathnames 683
23.1.5.4. Examples of the Use of
21.1. Standard Streams 535
Logical Pathnames 686
21.2. Creating New Streams 538
23.1.5.5. Discussion of Logical
21.3. Operations on Streams 542
Pathnames 688
23.1.6. Pathname Functions 690
22. Input/Output 547
23.2. Opening and Closing
22.1. Printed Representation of Lisp Files 700
Objects 547 23.3. Renaming, Deleting, and Other
22.1.1. What the Read Function File Operations 707
Accepts 548 23.4. Loading Files 712
22.1.2. Parsing of Numbers and 23.5. Accessing Directories 718
Symbols 554
22.1.3. Macro Characters 563 24. Errors 720
22.1.4. Standard Dispatching Macro
24.1. General Error-Signaling
Character Syntax 570
Functions 721
22.1.5. The Readtable 582
24.2. Specialized Error-Signaling
22.1.6. What the Print Function
Forms and Macros 726
Produces 593
24.3. Special Forms for Exhaustive
22.2. Input Functions 611
Case Analysis 729
22.2.1. Input from Character
Streams 611
25. Miscellaneous Features 732
22.2.2. Input from Binary
Streams 622 25.1. The Compiler 732
22.3. Output Functions 622 25.1.1. Compiler Diagnostics 740
CONTENTS ix
25.1.2. Compiled Functions 741 28. Common Lisp Object
25.1.3. Compilation Environment 742 System 831
25.1.4. Similarity of Constants 747
28.1. Programmer Interface
25.2. Documentation 751
Concepts 831
25.3. Debugging Tools 752
28.1.1. Error Terminology 832
25.4. Environment Inquiries 759
28.1.2. Classes 835
25.4.1. Time Functions 759
28.1.2.1. De(cid:12)ning Classes 836
25.4.2. Other Environment
28.1.2.2. Creating Instances of
Inquiries 763
Classes 837
25.5. Identity Function 765
28.1.2.3. Slots 837
28.1.2.4. Accessing Slots 839
26. Loop 767 28.1.3. Inheritance 841
28.1.3.1. Inheritance of Methods 841
26.1. Introduction 767
28.1.3.2. Inheritance of Slots and Slot
26.2. How the Loop Facility
Options 841
Works 767
28.1.3.3. Inheritance of Class
26.3. Parsing Loop Clauses 768
Options 843
26.3.1. Order of Execution 769
28.1.3.4. Examples 843
26.3.2. Kinds of Loop Clauses 770
28.1.4. Integrating Types and
26.3.3. Loop Syntax 773
Classes 843
26.4. User Extensibility 773
26.5. Loop Constructs 773 28.1.5. Determining the Class
26.6. Iteration Control 774 Precedence List 845
26.7. End-Test Control 785 28.1.5.1. Topological Sorting 848
26.8. Value Accumulation 789 28.1.5.2. Examples 848
26.9. Variable Initializations 795 28.1.6. Generic Functions and
26.10. Conditional Execution 798 Methods 851
26.11. Unconditional Execution 800 28.1.6.1. Introduction to Generic
26.12. Miscellaneous Features 802 Functions 851
26.12.1. Data Types 802 28.1.6.2. Introduction to
26.12.2. Destructuring 803 Methods 852
28.1.6.3. Agreement on Parameter
SpecializersandQuali(cid:12)ers 855
27. Pretty Printing 808 28.1.6.4. Congruent Lambda-Lists for
27.1. Introduction 808 All Methods of a
27.2. Pretty Printing Control Generic Function 856
Variables 809 28.1.6.5. Keyword Arguments in
27.3. Dynamic Control of the Generic Functions and
Arrangement of Output 810 Methods 856
27.4. Format Directive 28.1.7. Method Selection and
Interface 822 Combination 858
27.5. Compiling Format Control 28.1.7.1. Determining the Effective
Strings 825 Method 858
27.6. Pretty Printing Dispatch 28.1.7.2. Standard Method
Tables 826 Combination 861
x CONTENTS
28.1.7.3. Declarative Method 29. Conditions 939
Combination 863
29.1. Introduction 939
28.1.7.4. Built-in Method Combination
29.2. Changes in Terminology 941
Types 863
29.3. Survey of Concepts 942
28.1.8. Meta-objects 865 29.3.1. Signaling Errors 942
28.1.8.1. Metaclasses 866 29.3.2. Trapping Errors 944
28.1.8.2. Standard Metaclasses 866 29.3.3. Handling Conditions 946
28.1.8.3. Standard Meta-objects 866 29.3.4. Object-Oriented Basis of
28.1.9. Object Creation and Condition Handling 947
Initialization 867 29.3.5. Restarts 949
28.1.9.1. Initialization 29.3.6. Anonymous Restarts 949
Arguments 868 29.3.7. Named Restarts 951
28.1.9.2. Declaring the Validity of 29.3.8. Restart Functions 952
Initialization Arguments 869 29.3.9. Comparison of Restarts and
28.1.9.3. Defaulting of Initialization Catch/Throw 953
Arguments 870 29.3.10. Generalized Restarts 955
28.1.9.4. Rules for Initialization 29.3.11. Interactive Condition
Arguments 871 Handling 956
29.3.12. Serious Conditions 956
28.1.9.5. Shared-Initialize 873
29.3.13. Non-Serious Conditions 957
28.1.9.6. Initialize-Instance 874
29.3.14. Condition Types 957
28.1.9.7. De(cid:12)nitions of Make-Instance
29.3.15. Signaling Conditions 958
and Initialize-Instance 876
29.3.16. Resignaling Conditions 959
28.1.10. Rede(cid:12)ning Classes 878
29.3.17. Condition Handlers 959
28.1.10.1. Modifying the Structure of
29.3.18. Printing Conditions 960
Instances 879
29.4. Program Interface to the
28.1.10.2. Initializing Newly Added
Condition System 961
Local Slots 879
29.4.1. Signaling Conditions 961
28.1.10.3. Customizing Class
29.4.2. Assertions 964
Rede(cid:12)nition 880
29.4.3. Exhaustive Case Analysis 968
28.1.10.4. Extensions 880 29.4.4. Handling Conditions 970
28.1.11. Changing the Class of an 29.4.5. De(cid:12)ning Conditions 974
Instance 881 29.4.6. Creating Conditions 977
28.1.11.1. Modifying the Structure of 29.4.7. Establishing Restarts 978
an Instance 881 29.4.8. Finding and Manipulating
28.1.11.2. Initializing Newly Added Restarts 987
Local Slots 881 29.4.9. Warnings 989
28.1.11.3. Customizing the Change of 29.4.10. Restart Functions 990
Class of an Instance 882 29.4.11. Debugging Utilities 992
28.1.12. Reinitializing an 29.5. Prede(cid:12)ned Condition
Instance 882 Types 993
28.1.12.1. Customizing
Reinitialization 884
Appendix A. Series 1001
28.2. Functions in the Programmer
Interface 884 A.1. Introduction 1001
CONTENTS xi
A.2. Series Functions 1003
A.2.1. Scanners 1004
A.2.2. Mapping 1008
A.2.3. Truncation and Other Simple
Transducers 1011
A.2.4. Conditional and Other
Complex Transducers 1013
A.2.5. Collectors 1017
A.2.6. Alteration of Series 1020
A.3. Optimization 1022
A.3.1. Basic Restrictions 1023
A.3.2. Constraint Cycles 1024
A.3.3. De(cid:12)ning New Series
Functions 1027
A.3.4. Declarations 1028
A.4. Primitives 1030
Appendix B. Generators and
Gatherers 1036
B.1. Introduction 1036
B.2. Generators 1037
B.3. Gatherers 1037
B.4. Discussion 1039
Appendix C. Backquote 1040
References 1053
Index of X3J13 Votes 1058
Other Indexes 1064
xii CONTENTS
Preface
SECOND EDITION
Common Lisp has succeeded. Since publication of the (cid:12)rst edition of this
bookin1984,manyimplementorshaveuseditasade factostandardforLisp
implementation. Asaresult,itisnowmucheasiertoportlargeLispprograms
fromoneimplementationtoanother. CommonLisphasprovedtobeauseful
and stable platform for rapid prototyping and systems delivery in arti(cid:12)cial
intelligence and other areas. With experience gained in using Common Lisp
forsomanyapplications,implementorsfoundnoshortageofopportunitiesfor
innovation. OneoftheimportantcharacteristicsofLispisitsgoodsupportfor
experimental extension of the language; while Common Lisp has been stable,
it has not stagnated.
The1984de(cid:12)nitionofCommonLispwasimperfectandincomplete. Insome
cases this was inadvertent: some odd boundary situation was overlooked and
its consequences not speci(cid:12)ed, or different passages were in con(cid:13)ict, or some
propertyofLispwassowell-knownandtraditionallyrelieduponthatIforgot
to write it down. In other cases the informal committee that was de(cid:12)ning
Common Lisp could not settle on a solution, and therefore agreed to leave
some important aspect of the language unspeci(cid:12)ed rather than choose a less
than satisfactory de(cid:12)nition. An example is error handling; 1984 Common
Lisp had plenty of ways to signal errors but no way for a program to trap or
process them.
Over the next year I collected reports of errors in the book and gaps in
the language. In December 1985, a group of implementors and users met in
Boston to discuss the state of Common Lisp. I prepared two lists for this
meeting, one of errata and clari(cid:12)cations that I thought would be relatively
uncontroversial (boy, was I wrong!) and one of more substantial changes I
thought should be considered and perhaps voted upon. Others also brought
proposals to discuss. It became clear to everyone that there was now enough
interestinCommonLisp, anddependenceonitsstability, thatamoreformal
mechanism was needed for managing changes to the language.
xiii
xiv PREFACE (SECOND EDITION)
This realization led to the formation of X3J13, a subcommittee of ANSI
committeeX3,toproduceaformalAmericanNationalStandardforCommon
Lisp. That process is nearing completion. X3J13 has completed the bulk of
its technical work in rectifying the 1984 de(cid:12)nition and codifying extensions
to that de(cid:12)nition that have received widespread use and approval. A draft
standard is now being prepared; it will probably be available in 1990. There
will then be a period (required by ANSI) for public review. X3J13 must then
considerthecommentsitreceivesandrespondappropriately. Ifthecomments
result in substantial changes to the draft standard, multiple public review
periods may be required before the draft can be approved as an American
National Standard.
Fortunately, X3J13 has done an outstanding job of documenting its work.
For every change that came to a formal vote, a document was prepared that
described the problem to be solved and one or more solutions. For each
solutionthereisadetailedproposalforchangingthelanguage;arationale;test
casesthatdistinguishtheproposalfromthestatusquoorfromotherproposals
forsolvingthatproblem;discussionsofcurrentpractice,costtoimplementors,
costtousers,costofnotadoptingtheproposal,bene(cid:12)tsofadoption,aesthetic
criteria;andanyrelevantinformaldiscussionthatmayhaveprecededcreation
of the formal proposal. All of these proposal documents were made available
on-line as well as in paper form. By my count, by June 1989 some 186 such
proposals were approved as language changes. (This count does not include
many proposals that came before the committee but were rejected.)
The purpose of this second edition is to bridge the gap between the (cid:12)rst
editionandtheforthcomingANSIstandardforCommonLisp. Becauseofthe
requirementforformalpublicreview,itwillbesometimeyetbeforetheANSI
standard is (cid:12)nal. This book in no way resembles the forthcoming standard
(which is being written independently by Kathy Chapman of Digital Equip-
ment Corporation with assistance from the X3J13 Drafting Subcommittee).
I have incorporated into this second edition a great deal of material based
on the votes of X3J13, in order to give the reader a picture of where the
language is heading. My purpose here is not simply to quote the X3J13
documentsverbatimbuttoparaphrasethemandrelatethemtothestructure
of the (cid:12)rst edition. A single vote by X3J13 may be discussed in many parts
of this book, and a single passage of this book may be affected by many of
the votes.
I wish to be very clear: this book is not an official document of X3J13,
though it is based on publicly available material produced by X3J13. In
no way does this book constitute a de(cid:12)nitive description of the forthcoming
ANSI standard. The committee’s decisions have been remarkably stable (it