Know Go: Interfaces. generics, and iterators

Praise for Know Go....10 Introduction....11 About the book....11 About generics....11 Who is the book for?....12 What should I read first?....13 What will I learn from this book?....13 Completing the challenges....14 How do I install the Go tools?....14 Where are the code examples?....14 1. Interfaces....15 Programming with types....15 Specific programming....15 Generic programming....16 Interface types....16 Interface parameters....17 Polymorphism....19 Interfaces make code flexible....19 Constraining parameters with interfaces....19 Limitations of method sets....20 The empty interface: any....22 Type assertions and switches....23 Go, meet generics....24 How it started....24 How its going....24 2. Type parameters....26 Generic functions....26 Introducing T, the arbitrary type....26 Type parameters....27 Instantiation....27 Stencilling....29 Getting started....29 An Identity function....29 Instantiating Identity....30 Exercise: Hello, generics....31 Running the test....32 Composite types....33 Slices of some arbitrary type....34 Other generic composite types....34 Generic types....35 Defining a generic slice type....35 The elements all have the same type....36 Generic types need to be instantiated....36 Exercise: Group therapy....37 Generic function types....38 Generic functions as values....38 The type is always instantiated....39 There are no generic functions....40 Generic types as function parameters....41 Exercise: Lengthy proceedings....41 Constraining type parameters....42 We cant add any to any....43 Not every type is addable....43 3. Constraints....45 Method set constraints....45 Limitations of the any constraint....45 Basic interfaces....46 Exercise: Stringy beans....47 Type set constraints....49 Type elements....49 Using a type set constraint....49 Unions....50 The set of all allowed types....51 Intersections....52 Empty type sets....52 Composite type literals....53 A struct type literal....53 Access to struct fields....54 Some limitations of type sets....54 Constraints versus basic interfaces....54 Constraints are not classes....55 Approximations....56 Limitations of named types....57 Type approximations....57 Derived types....58 Exercise: A first approximation....59 Interface literals....61 Syntax of an interface literal....61 Omitting the interface keyword....62 Referring to type parameters....63 Exercise: Greater love....65 4. Operations....68 Arithmetic....68 An AddAnything function....69 The set of all numeric types....69 Exercise: Product placement....70 Ordered types....73 The > operator....73 Strings....75 An Ordered interface....75 The cmp.Ordered constraint....76 Multiple type parameters....77 Function on two (or more) types....77 Each type parameter is a distinct type....78 Functions on slice types....78 The problem with derived slice types....79 Parameterizing by slice and element type....81 And I need to know this because?....82 Comparable types....82 Not every type is comparable....83 Not every comparable type is ordered....83 There are infinitely many comparable types....84 The comparable constraint....84 Why is comparable predeclared?....85 Exercise: Duplicate keys....85 Abstract types....88 A Greatest function....88 The scope of type parameters....89 The zero value....90 Switching on abstract types....91 5. Types....94 Named types....94 Named basic types....95 Generic basic types....95 Generic type aliases....96 Generic slice types....96 There are no generic types....97 Slices of interface types....98 Generic map types....99 Maps of abstract element types....99 Multiple type parameters....100 Instantiating multiple type parameters....101 Generic struct types....101 Self-reference....102 Methods....103 Adding methods to generic types....103 Exercise: Empty promises....103 Parameterised methods....105 More generic composite types....105 Interfaces....106 Channels....106 6. Functions....108 Functions on container types....108 Contains....109 Reverse....110 Sort....111 First-class functions....112 Map....112 Type inference....114 Exercise: Func to funky....114 Filtering and reduction....117 Filter....117 Filter functions....118 Generic filter functions....119 Reduce....120 Implementing Reduce....121 Other reduction operations....122 Other considerations....123 Constraints....123 Concurrency....124 Exercise: Compose yourself....125 7. Containers....129 Sets....129 Maps as sets....130 Operations on sets....130 Designing the Set type....131 Building out the machinery....132 The Add method....132 The Contains method....132 Initialising with multiple values....133 Getting a sets members....134 A String method....135 Logic on sets....136 Union....136 Intersection....137 A real-life example....138 Exercise: Stack overflow....138 8. Concurrency....143 Data races....143 Mutexes....144 Deadlocks....144 A concurrency-safe set type....145 Locking....145 The constructor....146 A locking Add method....146 The read-locking methods....147 Testing concurrency safety....148 Smoke tests....148 A fatal error....149 The race detector....150 And the rest....151 Exercise: Channelling frustration....153 Extending the Set type....159 More set operations....159 Key-value stores and caches....160 Other container types....160 9. Packages....162 The cmp package....162 The slices package....163 Comparing slices....163 Finding elements....166 Maxima and minima....168 Inserting and deleting....168 Cloning and compacting....169 Growing and shrinking....170 Sorting....171 Reversing and replacing....172 Searching....173 The maps package....175 Comparing maps....175 Deleting map entries....175 Cloning and copying....176 New idioms....177 Copying slices....177 Deleting slice elements....177 Checking for slice elements....178 Exercise: Merging in turn....179 10. Questions....183 Change....183 How much do I need to know about generics?....183 Will generics drastically change the way I write Go?....184 Do I need to change my existing code?....185 Performance....186 What impact does generics have on performance?....186 Does generic code compile more slowly?....187 Downsides....188 Why didnt they use angle brackets?....188 Still no option types....190 Still no enums....190 No proper union types....191 No macros....191 No parameterised methods....192 No generic packages....192 No insert cool tech here....192 More change....193 Will there be a Go 2?....194 There will be changes to Go....195 It wont be Go 2....195 But there will be a successor to Go (someday)....196 11. Iterators....198 Introduction to iterators....198 Why are iterators useful?....199 The signature of an iterator function....200 Using iterators in programs....201 Single-value iterators: iter.Seq....201 Two-value iterators: iter.Seq2....202 Dealing with errors....204 Cleaning up....205 Embracing iterators....206 Composing iterators....206 When iterators beat channels....207 Standard library changes....208 Slices....208 Maps....209 About this book....211 Who wrote this?....211 Feedback....211 Get my free newsletter....211 Free updates to future editions....212 The Deeper Love of Go....212 The Power of Go: Tools....213 Further reading....213 Credits....214 Acknowledgements....215