Last week I had the opportunity to attend and speak at Northeast Scala Symposium, this is the story of my experience. The symposium has been gathering Scala enthusiasts for ten years now, and while most of the attendees come from the east-coast of the U.S., it’s usual for European folks to join as well. It’s really three different conferences on three successive days. The first day of talks is the Typelevel Summit, followed by the proper NE Scala lineup, and a day of unconference.

Type classes are a very common pattern in Scala. My goal in this post is to demystify what they are, how they are useful, and how they are supposed to evolve in the next big iteration of Scala, currently known as Dotty. Why do we need type classes ? Type classes are a programming technique that allows you to define common behavior for multiple types. Type classes act as a kind of interface, providing a common way of interacting with multiple types, while each of those type have different concrete implementation for this interface.