In this episode of the Haskell Interlude, we are joined by Sylvain Henry, one of the all-time top contributors to GHC. He tells us about his work on GHC, the bignum library, modularization, and the secret to becoming a top contributor!

This is the first part of a miniseries on this year’s Symposium on Principles of Programming Languages, a.k.a. POPL 2026, hosted by Jessica Foster.

In this episode we talk about: symbolic execution monads, what a lazy linear core in Haskell might have in common with Rust, hyperfunctions, the hallway track, and how to deal with rejection.

We talked to Fraser Tweedale. Fraser works at Red Hat, and is on the Haskell Security Response Team. We talked about security in the context of Haskell, both technical and organizational issues, and also the political issues involved. Fraser's work is both really important and not well-known in the Haskell ecosystem, so it was high time for him to come on the show.

Mike and Andres sat down with Torsten Grust, who is a professor of DB systems at the University of Tübingen. Even though Torsten loves SQL, he's used functional programming and Haskell to inform his work on query language design and compilation. We talked about the best way to program databases, how to bridge the gap between regular programming languages and databases, and compiling just about everything to SQL. 

This is the first part of a miniseries on this year’s Symposium on Principles of Programming Languages, a.k.a. POPL 2026, hosted by Jessica Foster.

In this episode, we talk about: undergrad funding and participation, the behind the scenes of AV, choreographic programming, quantum languages, conference catering, and the joy of theory. And at one point, you’ll even hear us get kicked out the venue mid interview. Enjoy!

Peter is a professor at the University of Freiburg, and he was doing functional programming right when Haskell got started. So naturally we asked him about the early days of Haskell, and how from the start Peter pushed the envelope on what you could do with the type system and specifically with the type classes, from early web programming to program generation to session types. Come with us on a trip down memory lane!

In this episode, we focus on a particular part of Haskell: teaching it. To help us, we are joined by Jamie Willis who is a Teaching Fellow at Imperial College London. The episode explores the benefits of live coding, and why Haskell is the best language for teaching programming.

Franz Thoma is Principal Consultant at TNG Technology Consulting, and an organizer of MuniHac. Franz sees functional programming and Haskell as a tool for thinking about software, even if the project is not written in Haskell. We had a far-reaching conversation about the differences between functional and object-oriented programming and their languages, software architecture, and Haskell adoption in industry. 

Welcome to the Haskell Interlude. Today, Matti and Mike talk to
Jeffrey Young. Jeff has had a long history of working with Haskell and
on ghc itself. We talk about what makes Haskell so compelling, the
good and bad of highly optimized code and the beauty of
well-modularized code, how to get into compiler development, and how
to benefit from Domain-Driven Design.

Jeff is currently on the job market - if you want to get in touch,
email him at mailto:[email protected].

We are joined by Kathrin Stark, a professor at Heriot-Watt University in Edinburgh. Kathrin works on program verification with proof assistants, so her focus is not exactly on Haskell, but on topics dear to Haskellers' hearts such as interactive theorem provers, writing correct programs, and the activities needed to produce them. We discuss many aspects of proofs and specifications, and the languages involved in the process, as well as verifying and producing provably correct neural networks.