Learning Functional Programming in Go: Change the way you approach your applications using functional programming in Go

Function literals, Monads, Lazy evaluation, Currying, and more About This Book Write concise and maintainable code with streams and high-order functions Understand the benefits of currying your Golang functions Learn the most effective design patterns for functional programming and learn when to apply each of them Build distributed MapReduce solutions using Go Who This Book Is For This book is for Golang developers comfortable with OOP and interested in learning how to apply the functional paradigm to create robust and testable apps. Prior programming experience with Go would be helpful, but not mandatory. What You Will Learn Learn how to compose reliable applications using high-order functions Explore techniques to eliminate side-effects using FP techniques such as currying Use first-class functions to implement pure functions Understand how to implement a lambda expression in Go Compose a working application using the decorator pattern Create faster programs using lazy evaluation Use Go concurrency constructs to compose a functionality pipeline Understand category theory and what it has to do with FP In Detail Functional programming is a popular programming paradigm that is used to simplify many tasks and will help you write flexible and succinct code. It allows you to decompose your programs into smaller, highly reusable components, without applying conceptual restraints on how the software should be modularized. This book bridges the language gap for Golang developers by showing you how to create and consume functional constructs in Golang. The book is divided into four modules. The first module explains the functional style of programming; pure functional programming (FP), manipulating collections, and using high-order functions. In the second module, you will learn design patterns that you can use to build FP-style applications. In the next module, you will learn FP techniques that you can use to improve your API signatures, to increase performance, and to build better Cloud-native applications. The last module delves into the underpinnings of FP with an introduction to category theory for software developers to give you a real understanding of what pure functional programming is all about, along with applicable code examples. By the end of the book, you will be adept at building applications the functional way. Style and approach This book takes a pragmatic approach and shows you techniques to write better functional constructs in Golan .. Contents 3 Preface 19 Pure Functional Programming in Go 28 Motivation for using FP 29 Getting the source code 30 Imperative versus declarative programming 32 Pure functions 35 Fibonacci sequence - a simple recursion and two performance improvements 36 The difference between an anonymous function and a closure 41 Testing FP using test-driven development 45 A journey from imperative programming to pure FP and enlightenment 53 Summary 57 Manipulating Collections 58 Iterating through a collection 59 Piping Bash commands 61 Functors 62 Predicates 74 Map and filter 78 Contains 84 If Go had generics 87 Itertools 89 Functional packages 93 Another time of reflection 93 The cure 94 Summary 97 High-Order Functions 98 Characteristics of FP 98 Sample HOF application 118 Summary 141 SOLID Design in Go 142 Why many Gophers loath Java 142 Software design methodology 149 SOLID design principles 152 The big reveal 170 Viva La Duck 175 Summary 185 Functionality with Decoration 186 Interface composition 187 Decorator pattern 193 A decorator implementation 197 Summary 223 Applying FP at Architectural Level 224 Application architectures 225 The role of systems engineering 229 Managing Complexity 231 FP influenced architectures 236 Domain Driven Design 236 A cloud bucket application 247 FP and Micyoservices 284 Summary 296 Functional Parameters 297 Refactoring long parameter lists 298 Functional parameters 314 Contexts 318 Summary 335 Pipelining 336 Introducing the pipeline pattern 337 Example implementations 342 Summary 360 Functors, Monoids & Generics 361 Understanding functors 361 Solve lack of generics with metaprogramming 369 Generics code generation tool 371 Generics implementation options 382 The shape of a functor 383 Composition operation 389 Functional composition in the context of a legal obligation 401 Build a 12-hour clock functor 406 The car functor 411 Monoids 416 Monoid examples 423 Summary 430 Monads, Type Classes & Generics 431 Mother Teresa Monad 432 Monadic workflow implementation 448 Y-Combinator 467 An alternative workflow option 471 Business use case scenarios 473 Y-Combinator re-examined 474 Type classes 488 Generics revisited 493 Summary 498 Category Theory 500 Our goal 501 Proof theory 514 The Curry Howard isomorphism 518 Historical Events in Functional Programming 520 Programming language categories 538 The Lambda Calculus 544 The importance of Type systems to FP 552 Domains, codomains, and morphisms 557 Set theory symbols 559 Category theory 560 Morphisms 567 Homomorphism 577 Composable concurrency 584 Graph Database Example 587 Using mathematics and category theory to gain understanding 588 Fun with Sums, Products, Exponents and Types 595 Big data, knowledge-driven development, and data visualization 601 Summary 606 Misc Info & How-to 607 How to build and run Go projects 607 Development workflow summary 629 How to propose changes to Go 635 FP resources 644 Minggatu - Catalan number 644 Index 648 Function literals, Monads, Lazy evaluation, Currying, and moreAbout This BookWrite concise and maintainable code with streams and high-order functionsUnderstand the benefits of currying your Golang functionsLearn the most effective design patterns for functional programming and learn when to apply each of themBuild distributed MapReduce solutions using GoWho This Book Is ForThis book is for Golang developers comfortable with OOP and interested in learning how to apply the functional paradigm to create robust and testable apps. Prior programming experience with Go would be helpful, but not mandatory.What You Will LearnLearn how to compose reliable applications using high-order functionsExplore techniques to eliminate side-effects using FP techniques such as curryingUse first-class functions to implement pure functionsUnderstand how to implement a lambda expression in GoCompose a working application using the decorator patternCreate faster programs using lazy evaluationUse Go concurrency constructs to compose a functionality pipelineUnderstand category theory and what it has to do with FPIn DetailLex Sheehan begins slowly, using easy-to-understand illustrations and working Go code to teach core functional programming (FP) principles such as referential transparency, laziness, recursion, currying, and chaining continuations.This book is a tutorial for programmers looking to learn FP and apply it to write better code. Lex guides readers from basic techniques to advanced topics in a logical, concise, and clear progression.The book is divided into four modules. The first module explains the functional style of programming: pure functional programming, manipulating collections, and using higher-order functions. In the second module, you will learn design patterns that you can use to build FP-style applications. In the next module, you will learn FP techniques that you can use to improve your API signatures, increase performance, and build better cloud-native applications. The last module covers Category Theory, Functors, Monoids, Monads, Type classes and Generics.By the end of the book, you will be adept at building applications the FP way.Style and approachThis book takes a pragmatic approach and shows you techniques to write better functional constructs in Golang. We'll also show you how use these concepts to build robust and testable apps.