Book Image

Haskell Design Patterns

By : Tikhon Jelvis, Ryan Lemmer
Book Image

Haskell Design Patterns

By: Tikhon Jelvis, Ryan Lemmer

Overview of this book

Design patterns and idioms can widen our perspective by showing us where to look, what to look at, and ultimately how to see what we are looking at. At their best, patterns are a shorthand method of communicating better ways to code (writing less, more maintainable, and more efficient code) This book starts with Haskell 98 and through the lens of patterns and idioms investigates the key advances and programming styles that together make "modern Haskell". Your journey begins with the three pillars of Haskell. Then you'll experience the problem with Lazy I/O, together with a solution. You'll also trace the hierarchy formed by Functor, Applicative, Arrow, and Monad. Next you'll explore how Fold and Map are generalized by Foldable and Traversable, which in turn is unified in a broader context by functional Lenses. You'll delve more deeply into the Type system, which will prepare you for an overview of Generic programming. In conclusion you go to the edge of Haskell by investigating the Kind system and how this relates to Dependently-typed programming
Table of Contents (14 chapters)

Summary


We followed the evolution of fold and map, starting with lists and then generalizing to all Foldable and Traversable containers.

Following that, we saw how the Lens library (2012) places folding and traversing in an even broader context. Lenses give us a unified vocabulary to navigate through data structures, which explains why it has been described as a "query language for data structures".

In this chapter, as we moved up the layers of abstraction, the function type signatures became ever more generic.

Genericity through type parameterization represents only one kind of generic programming. In Chapter 6, Patterns of Generic Programming, we explore more such patterns. But before we can do that, we need to add a few more advanced language extensions to our toolset. This is the subject of the next chapter.