Programming in Lua, 4th Edition, 2016.8

【实例截图】

【核心代码】

Table of Contents
About the Book ................................................................................................................. ix
I. The Basics ...................................................................................................................... 1
1. Getting Started ........................................................................................................ 4
Chunks .............................................................................................................. 4
Some Lexical Conventions ................................................................................... 6
Global Variables ................................................................................................. 7
Types and Values ................................................................................................ 7
Nil ............................................................................................................ 8
Booleans .................................................................................................... 8
The Stand-Alone Interpreter .................................................................................. 9
2. Interlude: The Eight-Queen Puzzle ............................................................................ 12
3. Numbers ............................................................................................................... 15
Numerals .......................................................................................................... 15
Arithmetic Operators .......................................................................................... 16
Relational Operators .......................................................................................... 17
The Mathematical Library ................................................................................... 18
Random-number generator .......................................................................... 18
Rounding functions .................................................................................... 18
Representation Limits ......................................................................................... 19
Conversions ...................................................................................................... 21
Precedence ....................................................................................................... 22
Lua Before Integers ........................................................................................... 22
4. Strings ................................................................................................................. 24
Literal strings .................................................................................................... 24
Long strings ..................................................................................................... 25
Coercions ......................................................................................................... 26
The String Library ............................................................................................. 27
Unicode ........................................................................................................... 29
5. Tables .................................................................................................................. 33
Table Indices .................................................................................................... 33
Table Constructors ............................................................................................. 35
Arrays, Lists, and Sequences ............................................................................... 36
Table Traversal ................................................................................................. 38
Safe Navigation ................................................................................................. 38
The Table Library ............................................................................................. 39
6. Functions .............................................................................................................. 42
Multiple Results ................................................................................................ 43
Variadic Functions ............................................................................................. 45
The function table.unpack ............................................................................ 47
Proper Tail Calls ............................................................................................... 48
7. The External World ................................................................................................ 50
The Simple I/O Model ....................................................................................... 50
The Complete I/O Model .................................................................................... 53
Other Operations on Files ................................................................................... 54
Other System Calls ............................................................................................ 55
Running system commands ......................................................................... 55
8. Filling some Gaps .................................................................................................. 57
Local Variables and Blocks ................................................................................. 57
Control Structures .............................................................................................. 58
if then else ............................................................................................... 58
while ....................................................................................................... 59
Programming in Lua, Fourth Edition
iv
repeat ..................................................................................................... 59
Numerical for ........................................................................................... 60
Generic for .............................................................................................. 60
break, return, and goto ..................................................................................... 61
II. Real Programming ......................................................................................................... 65
9. Closures ............................................................................................................... 68
Functions as First-Class Values ............................................................................ 68
Non-Global Functions ........................................................................................ 69
Lexical Scoping ................................................................................................ 71
A Taste of Functional Programming ..................................................................... 74
10. Pattern Matching .................................................................................................. 77
The Pattern-Matching Functions ........................................................................... 77
The function string.find ...................................................................... 77
The function string.match .................................................................... 77
The function string.gsub ...................................................................... 78
The function string.gmatch .................................................................. 78
Patterns ............................................................................................................ 78
Captures ........................................................................................................... 82
Replacements .................................................................................................... 83
URL encoding .......................................................................................... 84
Tab expansion ........................................................................................... 86
Tricks of the Trade ............................................................................................ 86
11. Interlude: Most Frequent Words ............................................................................. 90
12. Date and Time ..................................................................................................... 92
The Function os.time ..................................................................................... 92
The Function os.date ..................................................................................... 93
Date–Time Manipulation .................................................................................... 95
13. Bits and Bytes ..................................................................................................... 97
Bitwise Operators .............................................................................................. 97
Unsigned Integers .............................................................................................. 97
Packing and Unpacking Binary Data ..................................................................... 99
Binary files ..................................................................................................... 101
14. Data Structures ................................................................................................... 104
Arrays ............................................................................................................ 104
Matrices and Multi-Dimensional Arrays ............................................................... 105
Linked Lists .................................................................................................... 107
Queues and Double-Ended Queues ..................................................................... 107
Reverse Tables ................................................................................................ 108
Sets and Bags ................................................................................................. 109
String Buffers .................................................................................................. 110
Graphs ........................................................................................................... 111
15. Data Files and Serialization .................................................................................. 114
Data Files ....................................................................................................... 114
Serialization .................................................................................................... 116
Saving tables without cycles ...................................................................... 118
Saving tables with cycles .......................................................................... 119
16. Compilation, Execution, and Errors ....................................................................... 122
Compilation .................................................................................................... 122
Precompiled Code ............................................................................................ 125
Errors ............................................................................................................. 126
Error Handling and Exceptions .......................................................................... 127
Error Messages and Tracebacks .......................................................................... 128
17. Modules and Packages ........................................................................................ 131
The Function require .................................................................................... 132
Programming in Lua, Fourth Edition
v
Renaming a module ................................................................................. 133
Path searching ......................................................................................... 133
Searchers ................................................................................................ 135
The Basic Approach for Writing Modules in Lua .................................................. 135
Submodules and Packages ................................................................................. 137
III. Lua-isms ................................................................................................................... 139
18. Iterators and the Generic for ................................................................................ 142
Iterators and Closures ....................................................................................... 142
The Semantics of the Generic for ....................................................................... 143
Stateless Iterators ............................................................................................. 145
Traversing Tables in Order ................................................................................ 146
True Iterators .................................................................................................. 147
19. Interlude: Markov Chain Algorithm ....................................................................... 149
20. Metatables and Metamethods ................................................................................ 152
Arithmetic Metamethods ................................................................................... 152
Relational Metamethods .................................................................................... 155
Library-Defined Metamethods ............................................................................ 155
Table-Access Metamethods ............................................................................... 156
The __index metamethod ....................................................................... 156
The __newindex metamethod ................................................................. 157
Tables with default values ......................................................................... 158
Tracking table accesses ............................................................................. 159
Read-only tables ...................................................................................... 160
21. Object-Oriented Programming .............................................................................. 162
Classes ........................................................................................................... 163
Inheritance ...................................................................................................... 165
Multiple Inheritance ......................................................................................... 166
Privacy ........................................................................................................... 168
The Single-Method Approach ............................................................................ 170
Dual Representation ......................................................................................... 170
22. The Environment ................................................................................................ 173
Global Variables with Dynamic Names ............................................................... 173
Global-Variable Declarations ............................................................................. 174
Non-Global Environments ................................................................................. 176
Using _ENV .................................................................................................... 177
Environments and Modules ............................................................................... 180
_ENV and load .............................................................................................. 181
23. Garbage ............................................................................................................ 183
Weak Tables ................................................................................................... 183
Memorize Functions ......................................................................................... 184
Object Attributes ............................................................................................. 185
Revisiting Tables with Default Values ................................................................. 186
Ephemeron Tables ........................................................................................... 187
Finalizers ........................................................................................................ 188
The Garbage Collector ...................................................................................... 190
Controlling the Pace of Collection ...................................................................... 191
24. Coroutines ......................................................................................................... 194
Coroutine Basics .............................................................................................. 194
Who Is the Boss? ............................................................................................ 196
Coroutines as Iterators ...................................................................................... 198
Event-Driven Programming ............................................................................... 200
25. Reflection .......................................................................................................... 205
Introspective Facilities ...................................................................................... 205
Accessing local variables .......................................................................... 207
Programming in Lua, Fourth Edition
vi
Accessing non-local variables .................................................................... 208
Accessing other coroutines ........................................................................ 209
Hooks ............................................................................................................ 210
Profiles .......................................................................................................... 211
Sandboxing ..................................................................................................... 212
26. Interlude: Multithreading with Coroutines ............................................................... 217
IV. The C API ................................................................................................................ 221
27. An Overview of the C API .................................................................................. 223
A First Example .............................................................................................. 223
The Stack ....................................................................................................... 225
Pushing elements ..................................................................................... 226
Querying elements ................................................................................... 227
Other stack operations .............................................................................. 229
Error Handling with the C API .......................................................................... 231
Error handling in application code .............................................................. 232
Error handling in library code .................................................................... 232
Memory Allocation .......................................................................................... 233
28. Extending Your Application ................................................................................. 236
The Basics ...................................................................................................... 236
Table Manipulation .......................................................................................... 237
Some short cuts ....................................................................................... 240
Calling Lua Functions ...................................................................................... 241
A Generic Call Function ................................................................................... 242
29. Calling C from Lua ............................................................................................ 247
C Functions .................................................................................................... 247
Continuations .................................................................................................. 249
C Modules ...................................................................................................... 251
30. Techniques for Writing C Functions ...................................................................... 254
Array Manipulation .......................................................................................... 254
String Manipulation .......................................................................................... 255
Storing State in C Functions .............................................................................. 258
The registry ............................................................................................ 258
Upvalues ................................................................................................ 260
Shared upvalues ....................................................................................... 263
31. User-Defined Types in C ..................................................................................... 265
Userdata ......................................................................................................... 265
Metatables ...................................................................................................... 268
Object-Oriented Access ..................................................................................... 270
Array Access .................................................................................................. 271
Light Userdata ................................................................................................. 272
32. Managing Resources ........................................................................................... 274
A Directory Iterator .......................................................................................... 274
An XML Parser ............................................................................................... 277
33. Threads and States .............................................................................................. 286
Multiple Threads ............................................................................................. 286
Lua States ...................................................................................................... 289
vii
List of Figures
2.1. The eight-queen program .............................................................................................. 13
7.1. A program to sort a file ............................................................................................... 52
8.1. An example of a state machine with goto ........................................................................ 62
8.2. A maze game ............................................................................................................. 63
8.3. A strange (and invalid) use of a goto .............................................................................. 64
9.1. Union, intersection, and difference of regions ................................................................... 75
9.2. Drawing a region in a PBM file ..................................................................................... 75
11.1. Word-frequency program ............................................................................................ 91
12.1. Directives for function os.date ................................................................................. 94
13.1. Unsigned division ...................................................................................................... 98
13.2. Dumping the dump program ...................................................................................... 102
14.1. Multiplication of sparse matrices ................................................................................ 106
14.2. A double-ended queue .............................................................................................. 108
14.3. Reading a graph from a file ....................................................................................... 112
14.4. Finding a path between two nodes .............................................................................. 112
15.1. Quoting arbitrary literal strings ................................................................................... 117
15.2. Serializing tables without cycles ................................................................................. 118
15.3. Saving tables with cycles .......................................................................................... 120
16.1. Example of output from luac -l .............................................................................. 125
16.2. String repetition ....................................................................................................... 130
17.1. A homemade package.searchpath ...................................................................... 134
17.2. A simple module for complex numbers ........................................................................ 136
17.3. Module with export list ............................................................................................. 137
18.1. Iterator to traverse all words from the standard input ...................................................... 143
19.1. Auxiliary definitions for the Markov program ............................................................... 150
19.2. The Markov program ................................................................................................ 151
20.1. A simple module for sets .......................................................................................... 153
20.2. Tracking table accesses ............................................................................................. 159
21.1. the Account class .................................................................................................. 165
21.2. An implementation of multiple inheritance ................................................................... 167
21.3. Accounts using a dual representation ........................................................................... 171
22.1. The function setfield ........................................................................................... 174
22.2. Checking global-variable declaration ........................................................................... 176
23.1. Constant-function factory with memorization ................................................................ 187
23.2. Running a function at every GC cycle ......................................................................... 190
23.3. Finalizers and memory .............................................................................................. 192
24.1. Producer–consumer with filters ................................................................................... 198
24.2. A function to generate permutations ............................................................................ 199
24.3. An ugly implementation of the asynchronous I/O library ................................................. 201
24.4. Reversing a file in event-driven fashion ....................................................................... 202
24.5. Running synchronous code on top of the asynchronous library ......................................... 203
25.1. Getting the value of a variable ................................................................................... 208
25.2. Hook for counting number of calls .............................................................................. 211
25.3. Getting the name of a function ................................................................................... 212
25.4. A naive sandbox with hooks ...................................................................................... 213
25.5. Controlling memory use ............................................................................................ 214
25.6. Using hooks to bar calls to unauthorized functions ......................................................... 215
26.1. Function to download a Web page .............................................................................. 218
26.2. The dispatcher ......................................................................................................... 219
26.3. Dispatcher using select ......................................................................................... 220
27.1. A bare-bones stand-alone Lua interpreter ..................................................................... 224
Programming in Lua, Fourth Edition
viii
27.2. Dumping the stack ................................................................................................... 229
27.3. Example of stack manipulation ................................................................................... 231
28.1. Getting user information from a configuration file ......................................................... 236
28.2. A particular getcolorfield implementation ............................................................ 238
28.3. Colors as strings or tables ......................................................................................... 240
28.4. Calling a Lua function from C ................................................................................... 242
28.5. A generic call function .............................................................................................. 243
28.6. Pushing arguments for the generic call function ............................................................. 244
28.7. Retrieving results for the generic call function ............................................................... 245
29.1. A function to read a directory .................................................................................... 249
29.2. Implementation of pcall with continuations ............................................................... 251
30.1. The function map in C ............................................................................................. 255
30.2. Splitting a string ...................................................................................................... 256
30.3. The function string.upper ................................................................................... 257
30.4. A simplified implementation for table.concat ........................................................ 258
30.5. An implementation of tuples ...................................................................................... 262
31.1. Manipulating a Boolean array .................................................................................... 266
31.2. Extra code for the Boolean array library ...................................................................... 267
31.3. New versions for setarray/getarray .................................................................... 269
31.4. New initialization code for the Bit Array library ............................................................ 272
32.1. The dir.open factory function ................................................................................ 275
32.2. Other functions for the dir library ............................................................................. 276
32.3. Function to create XML parser objects ........................................................................ 280
32.4. Function to parse an XML fragment ............................................................................ 281
32.5. Handler for character data ......................................................................................... 282
32.6. Handler for end elements .......................................................................................... 282
32.7. Handler for start elements ......................................................................................... 283
32.8. Method to close an XML parser ................................................................................. 283
32.9. Initialization code for the lxp library .......................................................................... 284
33.1. Function to search for a process waiting for a channel .................................................... 291
33.2. Function to add a process to a waiting list .................................................................... 291
33.3. Functions to send and receive messages ....................................................................... 292
33.4. Function to create new processes ................................................................................ 293
33.5. Body for new threads ............................................................................................... 294
33.6. Extra functions for the lproc module ........................................................................ 295
33.7. Registering libraries to be opened on demand ............................................................... 296