《Thinking Functionally with Haskell》

【实例截图】

【核心代码】

Contents
Preface page ix
1 What is functional programming? 1
1.1 Functions and types 1
1.2 Functional composition 3
1.3 Example: common words 3
1.4 Example: numbers into words 7
1.5 The Haskell Platform 12
1.6 Exercises 14
1.7 Answers 17
1.8 Chapter notes 20
2 Expressions, types and values 22
2.1 A session with GHCi 22
2.2 Names and operators 25
2.3 Evaluation 27
2.4 Types and type classes 30
2.5 Printing values 33
2.6 Modules 35
2.7 Haskell layout 36
2.8 Exercises 37
2.9 Answers 42
2.10 Chapter notes 47
3 Numbers 49
3.1 The type class Num 49
3.2 Other numeric type classes 50
3.3 Computing floors 52
3.4 Natural numbers 56
vi Contents
3.5 Exercises 59
3.6 Answers 61
3.7 Chapter notes 62
4 Lists 63
4.1 List notation 63
4.2 Enumerations 65
4.3 List comprehensions 66
4.4 Some basic operations 68
4.5 Concatenation 69
4.6 concat, map and filter 70
4.7 zip and zipWith 73
4.8 Common words, completed 75
4.9 Exercises 77
4.10 Answers 82
4.11 Chapter notes 87
5 A simple Sudoku solver 89
5.1 Specification 89
5.2 Lawful program construction 95
5.3 Pruning the matrix of choices 97
5.4 Expanding a single cell 101
5.5 Exercises 105
5.6 Answers 107
5.7 Chapter notes 109
6 Proofs 110
6.1 Induction over natural numbers 110
6.2 Induction over lists 113
6.3 The function foldr 117
6.4 The function foldl 122
6.5 The function scanl 125
6.6 The maximum segment sum 127
6.7 Exercises 131
6.8 Answers 135
6.9 Chapter notes 144
7 Efficiency 145
7.1 Lazy evaluation 145
7.2 Controlling space 149
7.3 Controlling time 154
7.4 Analysing time 156
7.5 Accumulating parameters 159
Contents vii
7.6 Tupling 164
7.7 Sorting 167
7.8 Exercises 172
7.9 Answers 175
7.10 Chapter notes 180
8 Pretty-printing 181
8.1 Setting the scene 181
8.2 Documents 183
8.3 A direct implementation 187
8.4 Examples 189
8.5 The best layout 191
8.6 A term representation 193
8.7 Exercises 199
8.8 Answers 203
8.9 Chapter notes 209
9 Infinite lists 210
9.1 Review 210
9.2 Cyclic lists 212
9.3 Infinite lists as limits 215
9.4 Paper–rock–scissors 221
9.5 Stream-based interaction 226
9.6 Doubly-linked lists 228
9.7 Exercises 231
9.8 Answers 234
9.9 Chapter notes 237
10 Imperative functional programming 239
10.1 The IO monad 239
10.2 More monads 244
10.3 The State monad 247
10.4 The ST monad 251
10.5 Mutable arrays 254
10.6 Immutable arrays 259
10.7 Exercises 263
10.8 Answers 267
10.9 Chapter notes 275
11 Parsing 276
11.1 Parsers as monads 276
11.2 Basic parsers 279
11.3 Choice and repetition 281
viii Contents
11.4 Grammars and expressions 285
11.5 Showing expressions 288
11.6 Exercises 291
11.7 Answers 294
11.8 Chapter notes 297
12 A simple equational calculator 298
12.1 Basic considerations 298
12.2 Expressions 304
12.3 Laws 310
12.4 Calculations 312
12.5 Rewrites 315
12.6 Matchings 317
12.7 Substitutions 319
12.8 Testing the calculator 321
12.9 Exercises 331
12.10 Answers 333
12.11 Chapter notes 337
Index 338
Preface