A comprehensive example-driven guide to Optics. Examples in Haskell, but adaptable to other languages. Become a data-manipulation wizard using Optics to manipulate data! Lenses, also known as functional references, are a powerful way of looking at, constructing, and using functions on complex data types. They're also, unfortunately, a very new and complex subject making them challenging to learn. This book takes you from beginner to advanced using Lenses, Traversals, Prisms, and more! Optics By Example is a one-stop comprehensive guide to mastering Optics in functional programming languages. It covers everything you need to know to go from complete beginner to advanced. Each topic is accompanied by copious examples and exercises!