Today, 2023-10-25, at 1830 UTC (11:30 am PDT, 2:30 pm EDT, 7:30 pm BST, 20:30 CEST, …) we are streaming the thirteenth episode of the Haskell Unfolder live on YouTube.
The Haskell Unfolder Episode 13: open recursion
Open recursion is a technique for defining objects in Haskell whose behaviour can be adjusted after they have been defined. It can be used to do some form of object-oriented programming in Haskell, and is also an interesting technique in its own right.
Examples
In the episode we discuss two approaches: we first introduce something that
is reminiscent of the this keyword in OOP languages, and then we introduce
something more akin to the super keyword. We list the examples that we discuss
in the episode below as interactive programs that you can step through at your
own pace; doing so can be quite useful in understanding how these programs work
(these are generated using visualize-cbn).
First, the version of the counter without faster (we didn’t step through this
in the episode itself):
Next, the version where we do call faster:
And finally the version where we introduce super and mixin (which we called
(.+) in the episode):
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.