Book Image

Learning Functional Programming in Go

By : Lex Sheehan
Book Image

Learning Functional Programming in Go

By: Lex Sheehan

Overview of this book

Lex Sheehan begins slowly, using easy-to-understand illustrations and working Go code to teach core functional programming (FP) principles such as referential transparency, laziness, recursion, currying, and chaining continuations. This book is a tutorial for programmers looking to learn FP and apply it to write better code. Lex guides readers from basic techniques to advanced topics in a logical, concise, and clear progression. The book is divided into four modules. The first module explains the functional style of programming: pure functional programming, manipulating collections, and using higher-order functions. In the second module, you will learn design patterns that you can use to build FP-style applications. In the next module, you will learn FP techniques that you can use to improve your API signatures, increase performance, and build better cloud-native applications. The last module covers Category Theory, Functors, Monoids, Monads, Type classes and Generics. By the end of the book, you will be adept at building applications the FP way.
Table of Contents (21 chapters)
Title Page
Credits
About the Author
Acknowledgments
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface
Index

Monoid examples


We'll cover three types of monoid here:

  • Name monoid
  • Int slice monoid
  • Line item monoid

That's right. We're going to turn that invoice into a monoid!

Name monoid

Let's see what we can do with a name. First, we define an interface that has two methods, Append and Zero. We wrap our name in nameContainer.

Our nameContainer is a struct with a single string field, name. Our Append method appends the given name to the long name string it's building up that lives in the magical nameContainer. Our zero morphism for our name string is an empty string.

The content of src/monoid/name_monoid.go would look as follows:

package monoid

type NameMonoid interface {
   Append(s string) NameMonoid
   Zero() string
}

func WrapName(s string) NameMonoid {
return nameContainer{name: s}
}

type nameContainer struct {
   name string
}

func (s nameContainer) Append(name string) NameMonoid {
   s.name = s.name + name
return s
}

func (nameContainer) Zero() string {
return ""
}

func (s nameContainer) String...