Essential F#: Succinct. Robust. Performant

Table of Contents....3

Preface....7

Contents....8

F# Software Foundation....10

About the author....10

Acknowledgments....11

Getting Started....12

Setting up your environment....12

One Last Thing....13

1 - An Introductory Domain Modelling Exercise....14

The Problem....14

Getting Started....15

Making the Implicit Explicit....22

Going Further....24

Alternative Approaches (1 of 2)....27

Alternative Approaches (2 of 2)....28

Summary....30

Postscript....31

2 - Functions....32

Getting Started....32

Theory....32

In Practice....33

Unit....36

Anonymous Functions....37

Multiple Parameters....38

Partial Application (Part 1)....39

The Forward Pipe Operator....39

Partial Application (Part 2)....42

Summary....44

3 - Null and Exception Handling....45

Null Handling....45

Interop With .NET....48

Handling Exceptions....49

Function Composition With Result....51

Summary....57

4 - Organising Code and Testing....58

Getting Started....58

Solutions and Projects....58

Adding a Source File....58

Namespaces and Modules....59

Writing Tests....62

Writing Real Tests....63

Using FsUnit for Assertions....67

Summary....68

5 - Introduction to Collections....69

Before We Start....69

The Basics....69

Core Functionality....69

Folding....74

Grouping Data and Uniqueness....75

Solving a Problem in Many Ways....76

Working Through a Practical Example....77

Summary....85

6 - Reading Data From a File....86

Setting Up....86

Loading Data....86

Parsing Data....89

Testing the Code....91

Final Code....93

Summary....95

7 - Active Patterns....96

Setting Up....96

Partial Active Patterns....96

Parameterized Partial Active Patterns....98

Multi-Case Active Patterns....102

Single-Case Active Patterns....103

Using Active Patterns in a Practical Example....105

Summary....108

8 - Functional Validation....109

Setting Up....109

Solving the Problem....111

Where are we now?....116

Functional Validation the F# Way....120

Summary....123

9 - Single-Case Discriminated Union....124

Setting Up....124

Solving the Problem....124

Using Modules....131

A Few Minor Improvements....133

Using a Record Type....135

Summary....135

10 - Object Programming....136

Setting Up....136

Class Types....136

Interfaces....138

Object Expressions....140

Encapsulation....142

Equality....144

Summary....146

11 - Recursion....147

Setting Up....147

Solving The Problem....147

Tail Call Optimisation....148

Expanding the Accumulator....149

Using Recursion to Solve FizzBuzz....150

Quicksort using recursion....151

Recursion with Hierarchical Data....152

Other Uses Of Recursion....158

Summary....158

12 - Computation Expressions....159

Setting Up....159

Introduction....159

The Result Computation Expression....162

Introduction to Async....164

Compound Computation Expressions....165

Debugging Code....170

Further Reading....170

Summary....171

13 - Introduction to Web Programming with Giraffe....172

Getting Started....172

Using Giraffe....173

Creating an API Route....176

Creating a Custom HttpHandler....177

Creating a View....178

Adding Subroutes....179

Reviewing the Code....181

Summary....183

14 - Creating an API with Giraffe....184

Getting Started....184

Our Task....184

Sample Data....184

Routes....185

Handlers....187

Using the API....189

Summary....190

15 - Creating Web Pages with Giraffe....191

Getting Started....191

Configuration....191

Adding a Master Page....192

Creating the Todo List View....193

Loading Data on Startup....195

Summary....197

Summary....198

F# Software Foundation....199

Resources....199

And Finally....200

Appendix 1....201

Creating Solutions and Projects in VS Code....201

Appendix 2....203

CSS and JavaScript for Chapter 15....203

Everywhere you look, programming languages are gaining functional features. The problem is that it's not the individual features that make functional programmers happy, it's the way that your approach to writing software and the features work together to help you write simple code to solve interesting problems. This book will help you to discover why F# is such a popular language with those who have spent time learning its secrets. 

This book started life as a series of blog posts I wrote for the Trustbit website (https://trustbit.tech/blog). The sum of the content is the core of what a developer needs to know to be able to work on one of their F# Line of Business codebases. I have improved and extended the content, upgraded the code to F# 5, and ensured that the code would run in VS Code with the free ionide extension.

This book is FREE. If someone feels that they want to pay money for it, the author's royalties (80%) will continue to go to the F# Software Foundation.