Book Image

F# 4.0 Design Patterns

By : Gene Belitski
Book Image

F# 4.0 Design Patterns

By: Gene Belitski

Overview of this book

Following design patterns is a well-known approach to writing better programs that captures and reuses high-level abstractions that are common in many applications. This book will encourage you to develop an idiomatic F# coding skillset by fully embracing the functional-first F# paradigm. It will also help you harness this powerful instrument to write succinct, bug-free, and cross-platform code. F# 4.0 Design Patterns will start off by helping you develop a functional way of thinking. We will show you how beneficial the functional-first paradigm is and how to use it to get the optimum results. The book will help you acquire the practical knowledge of the main functional design patterns, the relationship of which with the traditional Gang of Four set is not straightforward. We will take you through pattern matching, immutable data types, and sequences in F#. We will also uncover advanced functional patterns, look at polymorphic functions, typical data crunching techniques, adjusting code through augmentation, and generalization. Lastly, we will take a look at the advanced techniques to equip you with everything you need to write flawless code.
Table of Contents (20 chapters)
F# 4.0 Design Patterns
Credits
About the Author
Acknowledgements
About the Reviewer
www.PacktPub.com
Preface

Named patterns


The F# compiler performs a certain analysis when a name (identifier) occurs in the position of a pattern case. Strictly speaking, there are some opportunities for the name to be as follows:

  • A named literal (such as THREE in the earlier script)

  • A case value of a discriminated union (such as None if matching an F# option)

  • A type of an exception (such as System.ArgumentException if matching an exception type)

  • A custom name of an active pattern (which will be covered in the upcoming chapters)

If the name occurrence does not fit any of the previously listed alternatives, the name is considered a variable pattern (https://msdn.microsoft.com/en-us/library/dd547125.aspx ). It is treated similarly to the wildcard pattern, getting the value of comparison-expression parameter, which can be used in the corresponding result-expression. Sounds confusing, right? Then let's turn to a sample in order to make this matter clear.

I just took the definition of the transformA function from the matching...