The Haskell Unfolder Episode 3: injectivity

Today, 2023-05-15, at 1830 UTC (11:30 am PDT, 2:30 pm EDT, 7:30 pm BST, 20:30 CEST, …) we are streaming the third episode of the Haskell Unfolder live on YouTube:

In this episode, we will discuss in what way parameterised datatypes are injective and type families are not. For this episode, we assume familiarity with Haskell fundamentals, in particular datatypes. Knowledge of type families is certainly helpful, but not required.

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. The playlist containing all episodes so far is here:

We also have a GitHub repository with the code samples from the episodes:

And we have a public Google calendar listing the planned schedule:

(or ICal: )


I appreciated the explanation around 21:22 of why using Proxy can be more readable than relying on AllowAmbiguousTypes.

These videos have been great so far!