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

Morphisms


A morphism is an arrow from one object (A, B, C in our example) in a category (our grouping of A, B, C). There can be more than one arrow from A to B (or from B to C, or A to C). Also, arrows can go from any object to itself; this is called the identity morphism.

  • f:A→B statement is a morphism (f) from A to B
  • Hom(A,B) is the collection of all arrows from A to B
  • Hom(A,B) is also known as the Hom-Set of A to B
  • idA:A→A is a morphism from A to A

The behaviors of morphisms

Let's look at at a couple things we can do with morphisms. W can compose them and run the identity morphism to verify an object's identity.

Composition operation

Below, is our basic composition operation.

The composition operation is g o f, g after f applies arg x (from A) to give us g applied to f applied to x: (g o f)(x) = g(f(x)).

If f(g(x)) = g(f(x)) for all x, then we can say that f and g commute under composition.

However, that's not typical. Function composition is generally not commutative.

Let's take an example. Remember...