The Type Astronaut's Guide to Shapeless—Dave Gurnell

Dave Gurnell introduces Shapeless, a library for generic programming in Scala, explaining generic representations, isomorphisms, and type class derivation.

This workshop is an introduction to shapeless, a library for generic programming in Scala. It is aimed at developers with little to no experience with shapeless. However, attendees should be confident with Scala and have a rough working knowledge of algebraic data types and type classes. We will introduce the main concepts used by shapeless, including generic representations, isomorphisms, and dependent and singleton types. We will then demonstrate programming techniques to abstract over types and eliminate boilerplate, paying special attention to one of shapeless' most exciting uses: automatic derivation of type class instances. Along the way, we will touch on the ways shapeless is being used in some of Scala's most ground-breaking open source projects, including Circe, Doobie, Ensime, Finch, frameless, parboiled2, and scodec.