Today, 2024-06-12, at 1830 UTC (11:30 am PDT, 2:30 pm EDT, 7:30 pm BST, 20:30 CEST, …) we are streaming the 27th episode of the Haskell Unfolder live on YouTube.

The Haskell Unfolder Episode 27: duality

“Duality” is the idea that two concepts are “similar but opposite” in some precise sense. The discovery of a duality enables us to use our understanding of one concept to help us understand the dual concept, and vice versa. It is a powerful technique in many disciplines, including computer science. In this episode of the Haskell Unfolder we discuss how we can use duality in a very practical way, as a guiding principle leading to better library interfaces and a tool to find bugs in our code.

This episode focuses on design philosophy rather than advanced Haskell concepts, and should consequently be of interest to beginners and advanced Haskell programmers alike (we will not use any Haskell beyond Haskell 2010). Indeed, the concepts apply in other languages also (but we will assume familiarity with Haskell syntax).

About the Haskell Unfolder

The Haskell Unfolder is a YouTube series about all things Haskell hosted by Edsko de Vries and Andres Löh, with episodes appearing approximately every two weeks. All episodes are live-streamed, and we try to respond to audience questions. All episodes are also available as recordings afterwards.

We have a GitHub repository with code samples from the episodes.

And we have a public Google calendar (also available as ICal) listing the planned schedule.

There’s now also a web shop where you can buy t-shirts and mugs (and potentially in the future other items) with the Haskell Unfolder logo.