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

Lazy evaluation


This concept is very simple. By default, F# follows the eager evaluation (https://en.wikipedia.org/wiki/Eager_evaluation) strategy, or an expression is evaluated as soon as it is bound. The alternative strategy available in other functional programming languages is to postpone the calculations until their result is absolutely necessary. F# can be explicitly told where to use lazy evaluation; by default, it uses lazy evaluations only for sequences. Expressing lazy evaluation if F# is not complicated syntactically, the following binding serves the purpose as shown:

let name = lazy ( expression ) 

Here, name is bound to the result of calculating expression, but the calculation itself is postponed. The type of value name is a special one, that is, Lazy<'T>; it represents a wrapper over 'T, which is the type of the expression per se. The computation gets performed by calling the Force method of type Lazy<'T>, like this name.Force(). This action also unwraps the underlying...