Book Image

Haskell Cookbook

Book Image

Haskell Cookbook

Overview of this book

Haskell is a purely functional language that has the great ability to develop large and difficult, but easily maintainable software. Haskell Cookbook provides recipes that start by illustrating the principles of functional programming in Haskell, and then gradually build up your expertise in creating industrial-strength programs to accomplish any goal. The book covers topics such as Functors, Applicatives, Monads, and Transformers. You will learn various ways to handle state in your application and explore advanced topics such as Generalized Algebraic Data Types, higher kind types, existential types, and type families. The book will discuss the association of lenses with type classes such as Functor, Foldable, and Traversable to help you manage deep data structures. With the help of the wide selection of examples in this book, you will be able to upgrade your Haskell programming skills and develop scalable software idiomatically.
Table of Contents (13 chapters)

Working with lenses

In this recipe, we will be working with the lens library. This library provides a whole battery of functions. We will be using some of those functions. We will also create lenses for our own data type.

How to do it...

  1. Create a new project working-with-lenses, with a simple stack template:
        stack new working-with-lenses simple
  1. Add a dependency on lens library in the build-depends sub-section of the executable section:
        executable working-with-lenses
         hs-source-dirs:      src
         main-is:             Main.hs
         default-language:    Haskell2010
         build-depends:       base >= 4.7 && < 5
                              , lens
  1. Open src/Main.hs. We will...