Type Theory Forall

Lennart Augustsson has spent the last four decades quietly — and sometimes mischievously — shaping the way we think about code. He co-authored Lazy ML in the early 80s, wrote A Compiler for LML back in 1984, and was behind HBC, the first publicly available Haskell compiler. If you've used Haskell, worked with hardware described in Bluespec, or played around with weird combinator-based toy languages, there's a decent chance you've crossed paths with his ideas — directly or indirectly. He's also won the International Obfuscated C Code Contest — not once, but multiple times — reminding us that playfulness and rigor aren't mutually exclusive. But his work didn't stop in academia or hobby projects. He’s brought functional programming into finance, hardware design, large-scale industry — with stints at Credit Suisse, Facebook, Google, and now Epic Games, where he’s helping design a new functional logic programming language called Verse. Over the course of this conversation, we’ll talk about lazy evaluation, type theory, programmable dungeons, the compromises of real-world programming, and what it means to still be building languages after 40 years in the game. Links Type Theory Forall Merch Store Ko-Fi Discord Server Haskell Interlude Lennart's Wikipedia Page Lennart's Webpage

In this episode we talk with Nicolas Tabareau, the Head of Gallinette, one of the main teams which develop the Rocq theorem Prover at Inria. The original idea of this interview is to talk about the rebranding from Coq into Rocq, which is very exciting to our community. However, Nicolas has such a prolific research career that I couldn’t miss the opportunity to get him to talk so much more about it. So in this conversation we talk about his early publications in neuroscience, his views on Category Theory applied to Type Theory, Rocq’s rebranding, and the institution around it, MetaRocq and the conceptual boundaries of certifying a theory inside itself. Of course we wouldn’t miss the opportunity to also discuss how Rocq view the growing influence that Lean is gaining in our community. Links Type Theory Forall Store Type Theory Forall Website Nicolas Tabareau Website MetaRocq Github

Wouter Swierstra is a Math Bachelor’s from the University of Utrecht, has done his PhD with Thorsten Altenkirch at the University of Nottingham, did a post-doc at Chalmers, has experience in the industry working on facilitating the design of embedded system using FP and currently is a Professor at the University of Utrecht and co-host of the Haskell Interlude Podcast. In this episode we talk about his trajectory into formal methods and functional programming. We talk about Datatypes a la Carte, the Expression Problem, Functional Pearls, Program Synthesis vs Program Calculation, and much more! 0:00 – Intro & Welcome 0:02:08 – Announcing the Type Theory Forall Merch Store! 1:12 – Early Influences: From Lenses to Logic 4:40 – Discovering Functional Programming in Utrecht 8:15 – On Monads, Papers, and Learning by Teaching 12:20 – What Makes a Paper ‘Beautiful’? 17:50 – PhD in Nottingham: Theory Meets Community 22:00 – Writing ‘Certified Programming with Dependent Types’ 29:10 – Teaching Dependent Types: Challenges and Joys 34:00 – On Agda vs Coq: Philosophies and Use Cases 38:40 – Type-Driven Development in Practice 45:05 – The Power of Elegant Proofs 52:00 – Advice to Aspiring Researchers in Type Theory 1:03:00 – Beating C with Functional Programming 1:20:00 – Formal Verification and Loop Invariants 1:33:28 – Program Calculation vs Program Synthesis 1:39:00 – Formalizing Blockchain 2:01:38 – Final Thoughts Links Wouter Website Haskell Interlude Advanced FP Summer School ttforall twitch ttforall store Discount code for 10% off: typetheory

Ryan Brewer, a self-taught programming language expert and creator of innovative projects like Saber VM, shares his journey from college dropout to blog writer, dedicated to making formal theory accessible. Joined by researcher Dan Plukin, they discuss the challenges and joys of self-education in programming, the intersection of ethics and technology, and their experiences with compilers. They emphasize the importance of passion in learning and critique traditional academic paths, while encouraging openness in the programming community.

In this episode we continue with our conversation with David MacQueen, he is an Emeritus Professor from the University of Chicago, and has worked at Bell Labs for 20 years. Bell Labs began as the research and development section of the American Telephone and Telegraph company, aka AT&T, which originally hold exclusive hold of the telephone patent. Once that expired in the 1800s they needed to develop new technology to prove that it was still the best company, and hence Bell Labs was born. Over the course of the years this fascinating institution has registered more than 26 thousand patents, among of which we have the transistor, the laser, the solar cell and communication satellites. Over the course of the last 88 years they were awarded a jaw dropping amount of 10 Nobel prizes and 5 Turing awards. In this interview David MacQueen shares with us how was it like to work in such an incredible institution during it’s golden age. He shares insights about the technology, the space, the people, the management style, and much more! Links David's Website David's Github

David MacQueen has worked at Bell Labs for around 20 years during it’s Golden Age. Professor at Chicago University for 23 years. He is one of the designers of SML, one of the fathers of HOPE the programming language that introduced the notion of Algebraic Datatypes. So this interview was very special to me personally where I could get to hear all the stories about the dawn of Functional Programming as we know. And it is my great pleasure to have the honor to share it with you all. Links David's Website David's Github Luca Cardelli and the Early Evolution of ML The History of SML HOPE SML Website SML/NJ Website SML/NJ Github SML Family Website

In this episode Pierre-Marie Pédrot, one of the main Coq/Rocq developers joins us to talk about Krivine, Kleene and Gödel Realizability Models, how it relates to the BHK interpretation and CPS Translations, and how it was all already part of Gödel's work in Dialectica! If you enjoy the show please consider supporting us at our ko-fi: https://ko-fi.com/typetheoryforall Links Pierre-Marie's Website Pierre-Marie's PhD Thesis (Very nice read) BHK Interpretation Type Theory Forall website Type Theory Forall discord

In this episode Pierre-Marie Pédrot who is one of the main Coq/Rocq developers joins us to talk about what is Type Theory, what is Martin-Löf Type Theory, what are the properties we should care about in our type theory and why. If you enjoy the show please consider supporting us at our ko-fi: https://ko-fi.com/typetheoryforall Links Pierre-Marie's Website Type Theory Forall website Type Theory Forall discord

Mario Carneiro is a postdoc at Chalmers University and the creator of Mathlib and Metamath0, focusing on theorem provers and formal verification. He discusses the evolution of the Lean proof assistant, tackling challenges in type theory and interoperability of proof systems. The conversation includes insights on the user experience in proof systems, the introduction of MetaMath Zero, and the importance of community collaboration in development. Carneiro also reflects on the complexities of proof assistants and the necessity of efficient theorem proving.

In this episode Eric Bond and Patrick Lafontaine joins us to talk about the life in industry vs the life in academia. Eric is a PhD student at Michigan University under Max New, he works with some pretty cool esoteric cubical agda stuff. Before starting his PhD he has spent some time at the consultancy companies Two Six Technologies and 47 Degrees doing some cool functional programming and formal methods. Before that we were pals doing an internship at Galois, and even before that he finished his masters with Benjamin Delaware at Purdue, Patrick’s current advisor. Patrick has just returned from his internship at AWS in the automated reasoning team. So in this episode we talk about their research, their academic and industry experiences, how’s the industry looking like for opportunities in PL and all that. If you enjoy the show please consider supporting us at our ko-fi: https://ko-fi.com/typetheoryforall