Preface

This book is different from many other programming books available today. It doesn’t focus only on a specific programming language or library. Instead, it uses the presented languages and libraries to explain a way of thinking—a way of thinking that is becoming increasingly important and has influenced many recent technologies.

You may already know some of the concepts described in this book, because functional ideas appear in many technologies. Examples from the .NET world include C# 3.0 and the LINQ project, Microsoft Parallel Extensions to .NET, and the declarative programming model used in Windows Presentation Foundation (WPF). In this book we’ll build on top of your existing .NET and C# experience to explain the functional programming paradigm. We’ll introduce F#, Microsoft’s new functional programming language, and use it to turn abstract ideas into something more concrete. Where possible we’ll also use C#, because functional ideas can help you when designing C# applications.

If we’d been writing a book solely about F#, we could have simply organized it based on the individual language features and explained those features one by one. This book is about functional programming in general, so the structure is loosely based on ideas that form the functional paradigm. This is more difficult, because ideas don’t have clear boundaries and often overlap.