Today, 2024-03-20, at 1930 UTC (12:30 pm PDT, 3:30 pm EST, 7:30 pm GMT, 20:30 CET, …) we are streaming the 22th episode of the Haskell Unfolder live on YouTube.

The Haskell Unfolder Episode 22: foldr-build-fusion

When composing several list-processing functions, GHC employs an optimisation called foldr-build fusion. Fusion combines functions in such a way that any intermediate lists can often be eliminated completely. In this episode, we will look at how this optimisation works, and at how it is implemented in GHC: not as built-in compiler magic, but rather via user-definable rewrite rules.

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.