An introduction to programming in emacs lisp

314 Pages·2001·1.058 MB·English

by  Robert J. Chassell

An Introduction to
Programming in Emacs Lisp

An Introduction to
Programming in Emacs Lisp
Second Edition
by Robert J. Chassell
Copyright (cid:13)c 1990, 1991, 1992, 1993, 1994, 1995, 1997, 2001, 2002 Free
Software Foundation, Inc.
Published by the Free Software Foundation, Inc.
59 Temple Place, Suite 330
Boston, MA 02111-1307 USA
Edition 2.05, 2001 Jan 5
ISBN 1-882114-43-4
Permissionisgrantedtocopy, distributeand/ormodifythisdocumentunder
the terms of the GNU Free Documentation License, Version 1.1 or any later
version publishedby the Free Software Foundation; there being no Invariant
Section, with the Front-Cover Texts being \A GNU Manual", and with the
Back-Cover Texts as in (a) below. A copy of the license is included in the
section entitled \GNU Free Documentation License".
(a) The FSF’s Back-Cover Text is: \You have freedom to copy and modify
thisGNUManual,likeGNUsoftware. CopiespublishedbytheFreeSoftware
Foundation raise funds for GNU development."
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Short Contents
Preface......................................... xi
1 List Processing................................. 1
2 Practicing Evaluation ........................... 23
3 How To Write Function De(cid:12)nitions .................. 29
4 A Few Bu(cid:11)er{Related Functions.................... 51
5 A Few More Complex Functions .................... 63
6 Narrowing and Widening......................... 77
7 car, cdr, cons: Fundamental Functions ............. 81
8 Cutting and Storing Text......................... 89
9 How Lists are Implemented....................... 113
10 Yanking Text Back ............................ 117
11 Loops and Recursion ........................... 121
12 Regular Expression Searches...................... 149
13 Counting: Repetition and Regexps.................. 167
14 Counting Words in a defun...................... 181
15 Readying a Graph............................. 203
16 Your ‘.emacs’ File............................ 213
17 Debugging .................................. 231
18 Conclusion.................................. 239
Appendix A The the-the Function .................. 241
Appendix B Handling the Kill Ring ................... 243
Appendix C A Graph with Labelled Axes ............... 255
Appendix D GNU Free Documentation License ........... 279
Index......................................... 287
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iii
Table of Contents
Preface ...................................... xi
On Reading this Text........................................ xi
For Whom This is Written................................... xii
Lisp History............................................... xiii
A Note for Novices......................................... xiii
Thank You ................................................ xiv
1 List Processing ............................ 1
1.1 Lisp Lists............................................... 1
1.1.1 Lisp Atoms .................................... 1
1.1.2 Whitespace in Lists............................. 3
1.1.3 GNU Emacs Helps You Type Lists............... 3
1.2 Run a Program ......................................... 4
1.3 Generate an Error Message .............................. 4
1.4 Symbol Names and Function De(cid:12)nitions .................. 6
1.5 The Lisp Interpreter..................................... 7
1.5.1 Byte Compiling................................. 8
1.6 Evaluation.............................................. 8
1.6.1 Evaluating Inner Lists .......................... 9
1.7 Variables.............................................. 10
1.7.1 Error Message for a Symbol Without a Function.. 11
1.7.2 Error Message for a Symbol Without a Value.... 11
1.8 Arguments............................................. 12
1.8.1 Arguments’ Data Types........................ 13
1.8.2 An Argument as the Value of a Variable or List.. 13
1.8.3 Variable Number of Arguments................. 14
1.8.4 Using the Wrong Type Object as an Argument .. 14
1.8.5 The message Function......................... 16
1.9 Setting the Value of a Variable.......................... 17
1.9.1 Using set..................................... 17
1.9.2 Using setq.................................... 18
1.9.3 Counting...................................... 19
1.10 Summary............................................. 20
1.11 Exercises............................................. 20
2 Practicing Evaluation ..................... 23
2.1 Bu(cid:11)er Names.......................................... 23
2.2 Getting Bu(cid:11)ers ........................................ 25
2.3 Switching Bu(cid:11)ers ...................................... 26
2.4 Bu(cid:11)er Size and the Location of Point.................... 27
2.5 Exercise............................................... 28
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3 How To Write Function De(cid:12)nitions ........ 29
3.1 The defun Special Form................................ 29
3.2 Install a Function De(cid:12)nition ............................ 31
3.2.1 Change a Function De(cid:12)nition................... 32
3.3 Make a Function Interactive ............................ 33
3.3.1 An Interactive multiply-by-seven............. 34
3.4 Di(cid:11)erent Options for interactive...................... 35
3.5 Install Code Permanently............................... 36
3.6 let................................................... 36
3.6.1 The Parts of a let Expression.................. 37
3.6.2 Sample let Expression......................... 38
3.6.3 Uninitialized Variables in a let Statement....... 39
3.7 The if Special Form ................................... 39
3.7.1 The type-of-animal Function in Detail......... 41
3.8 If{then{else Expressions................................ 42
3.9 Truth and Falsehood in Emacs Lisp ..................... 43
3.10 save-excursion...................................... 44
3.10.1 Template for a save-excursion Expression .... 45
3.11 Review............................................... 46
3.12 Exercises............................................. 50
4 A Few Bu(cid:11)er{Related Functions........... 51
4.1 Finding More Information .............................. 51
4.2 A Simpli(cid:12)ed beginning-of-buffer De(cid:12)nition............ 52
4.3 The De(cid:12)nition of mark-whole-buffer................... 54
4.3.1 Body of mark-whole-buffer................... 55
4.4 The De(cid:12)nition of append-to-buffer.................... 56
4.4.1 The append-to-buffer Interactive Expression... 57
4.4.2 The Body of append-to-buffer................ 57
4.4.3 save-excursion in append-to-buffer.......... 58
4.5 Review................................................ 60
4.6 Exercises.............................................. 61
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5 A Few More Complex Functions........... 63
5.1 The De(cid:12)nition of copy-to-buffer....................... 63
5.2 The De(cid:12)nition of insert-buffer........................ 64
5.2.1 The Interactive Expression in insert-buffer.... 65
A Read-only Bu(cid:11)er............................ 65
‘b’ in an Interactive Expression................. 65
5.2.2 The Body of the insert-buffer Function....... 65
5.2.3 insert-buffer With an if Instead of an or..... 66
5.2.4 The or in the Body............................ 67
5.2.5 The let Expression in insert-buffer.......... 68
5.3 Complete De(cid:12)nition of beginning-of-buffer............ 69
5.3.1 Optional Arguments........................... 70
5.3.2 beginning-of-buffer with an Argument....... 71
What happens in a large bu(cid:11)er................. 71
What happens in a small bu(cid:11)er................ 72
5.3.3 The Complete beginning-of-buffer........... 73
5.4 Review................................................ 74
5.5 optional Argument Exercise ........................... 75
6 Narrowing and Widening.................. 77
6.1 The save-restriction Special Form.................... 77
6.2 what-line............................................. 78
6.3 Exercise with Narrowing................................ 79
7 car, cdr, cons: Fundamental Functions ..... 81
7.1 car and cdr........................................... 81
7.2 cons.................................................. 83
7.2.1 Find the Length of a List: length.............. 84
7.3 nthcdr................................................ 85
7.4 nth................................................... 86
7.5 setcar................................................ 87
7.6 setcdr................................................ 88
7.7 Exercise............................................... 88
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8 Cutting and Storing Text ................. 89
8.1 zap-to-char.......................................... 90
8.1.1 The interactive Expression................... 90
8.1.2 The Body of zap-to-char...................... 91
8.1.3 The search-forward Function ................. 92
8.1.4 The progn Special Form ....................... 93
8.1.5 Summing up zap-to-char..................... 93
8.2 kill-region.......................................... 94
8.2.1 condition-case............................... 95
8.2.2 delete-and-extract-region.................. 96
8.3 delete-and-extract-region: Digressing into C ......... 98
8.4 Initializing a Variable with defvar..................... 100
8.4.1 defvar and an asterisk........................ 101
8.5 copy-region-as-kill................................. 102
8.5.1 The Body of copy-region-as-kill............ 103
The kill-append function.................... 104
The kill-new function....................... 105
8.6 Review............................................... 109
8.7 Searching Exercises.................................... 111
9 How Lists are Implemented .............. 113
9.1 Symbols as a Chest of Drawers......................... 115
9.2 Exercise.............................................. 116
10 Yanking Text Back ..................... 117
10.1 Kill Ring Overview................................... 117
10.2 The kill-ring-yank-pointerVariable ............... 117
10.3 Exercises with yank and nthcdr....................... 119
11 Loops and Recursion.................... 121
11.1 while............................................... 121
11.1.1 A while Loop and a List..................... 122
11.1.2 An Example: print-elements-of-list...... 123
11.1.3 A Loop with an Incrementing Counter........ 124
Example with incrementing counter ........... 125
The parts of the function de(cid:12)nition............ 126
Putting the function de(cid:12)nition together........ 127
11.1.4 Loop with a Decrementing Counter........... 129
Example with decrementing counter........... 129
The parts of the function de(cid:12)nition............ 130
Putting the function de(cid:12)nition together........ 130
11.2 Save your time: dolist and dotimes.................. 131
The dolist Macro........................... 132
The dotimes Macro.......................... 133