Kit Eason - Stylish F# 6: Crafting Elegant Functional Code for .NET 6

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There are three distinct philosophies which you can apply to computer programming. You can think of programming as a science, where the measure of progress is how well you discover and reflect fundamental mathematical concepts in your code. You can think of it as a discipline, where you seek to establish and follow rules about how code should be written and organized. Or, best of all, you can think of it as a craft, where, yes, you apply some of the science and some of the discipline; but you leaven those with a generous helping of human creativity. To do this successfully, you need a fair bit of experience, because crafting something is an inherently intuitive process. This book aims to get you to a level where you can craft code confidently. It does this by distilling and passing on my own experience of writing F# systems in numerous different industries over the past ten years.

Before you start this book, youll need at least some knowledge of F# syntax and concepts. Maybe youve read some of the wide range of beginner material thats available, and probably youll have written at least a few simple F# programs yourself. You may well have deeper experience of other languages, such as C# or Python. That said, I have framed the book so that C# knowledge is not a hard prerequisite: I learned F# before I learned C#, and if I can do it, so can you! Also you definitely dont need any background in computer science or functional programming. I dont have even a trace of formal education in either of these areas.

So whats between the covers? In Chapter , Ill briefly reiterate what weve learned.

As this book is primarily about the language, youll find relatively few references to other libraries. Of course, to build substantial systems, youll almost always want to pull in NuGet packages for requirements such as unit testing, serialization, web serving, and so forth. But these libraries constitute a large and fast-changing landscape, so Ive chosen to pare things down to the F# essentials for this book. For the same reason, I hardly mention graphical user interface or web development. Since the first edition of this book, F# has become much more widely used in these areas, but this has been via innovations in the surrounding ecosystem (notably the Fable transpiler), whereas in these pages, I want to concentrate on the F# language itself.

This focus also means that most of the code examples can be typed in and run as cells in a .NET Interactive notebook. They are provided in notebook form in the downloadable code samples. In the small number of cases where you need to write a compilable program, I take you through the process in the text alongside the example. These non-notebook examples are also provided in the downloadable code but in project form so that you can open and build them in Visual Studio Code (with the Ionide extension), Visual Studio, or JetBrains Rider.

I very much hope you enjoy sharing my F# experience as much as I enjoyed acquiring it. Dont forget to have fun!

I am grateful for the generous help I received in putting Stylish F# together. Thanks to Stachu Korick (Second Edition) and Quinton Coetzee (First Edition) for their exceedingly diligent and constructive technical reviews. To Val Eason for detecting many typos and poor turns of phrase. To Dr. Jon Harrop for providing detailed technical feedback on Chapter . To Don Syme, Phillip Carter, and the F# community for the never-ending stream of compiler and tooling improvements that propel F# forward. And to Matt Jones and the amazing team at Perpetuum for providing the best working environment Ive ever experienced. Thanks also to the tireless crew at Apress: Joan Murray, Jill Balzano, and Laura Berendson. Any errors, omissions, or plain wrong-headedness are, of course, still my own responsibility.