Type Theory Forall

In this episode we continue our conversation with David Christiansen, he wrote the books Functional Programming in Lean and the Little Typer. He has also worked as the Executive Director of the Haskell Foundation, at Galois and did his PhD developing a bunch of cool stuff for Idris. In today’s episode we talk about the story behind writing The Little Typer together with Dan Friedman, and we get more technical by talking about Equality, Bidirectional Type Checking, Quotation and Quasi Quotation. Some links: David's Website David's X Lean Zulip Chat Truth of a proposition, evidence of a judgement, validity of a proof

In this episode we talk with David Christiansen, he wrote the books Functional Programming in Lean and the Little Typer. He has also worked as the Executive Director of the Haskell Foundation, at Galois and did his PhD developing a bunch of cool stuff for Idris. David is a super upbeat person and I feel that we could spend hundreds of hours talking about Functional Programming Writing and Dependent Types, and we still wouldn’t run out of topics!

In this episode we talk with Guannan Wei, from Purdue University. Guannan finished his PhD last year under Tiark Rompf, and is currently doing his Post-Doc with Tiark. Guannan has worked on a plethora of different compilers topics, and in this conversation we will talk about Staging, Futamura Projections, Symbolic Execution, Compiler Applications in Smart Contracts and Quantum Programming. Towards the end of the episode we also talk about his application experiences for the position of a Professorship in the US an a few other contries. Guannan's Website @guannanwei on X

In this episode we celebrate 3 years of existence of this podcast by reflecting on the journey so far, what is my philosophy, how do I approach the interviews, my overall goals for the show, and some of our plans for the future. In order to achieve this, I first take a detour and tell you a little more about my personal history, and my carreer in type theory and programming languages.

In this episode we talk with Eduardo Rafael. He is self-thaught programming languages enthusiast, youtuber, twitch streamer, multi-skilled programmer that has worked in different aspects of computer science such as PL, operating systems, blockchain, and many other stuff. In this conversation we talk about his experience as a developer and hacker that didn’t follow the conventional paths of going to school and what are the strategies to navigate the vast ocean of knowledge without guidance of teachers or institutions. Links Eduardo's Twitter Eduardo's Twitch Eduardo's Youtube Feynman Algorithm

Andrew Marmaduke is a PhD Candidate from the University of Iowa, he works under Aaron Stump and has been working on revamping the theorem prover Cedille 2. In this episode we tackle fundamental questions about the foundations of the theorem provers, Cedille and Cedille 2. Links Andrew's Website AndrasKovacs' Smalltt Failure of Normalization in Impredicative Type Theory with Proof-Irrelevant Propositional Equality Impredicative Encodings of (Higher) Inductive Types

Not satisfied with implementing one of the most popular automated theorem provers, Z3, Leo de Moura also tackles another extremely hard problem in our field and implements a brand new interactive theorem prover from scratch, Lean. In this episode we dive into the mind and philosophy of this man. Links Leo's Website Lean Z3 The Church of Logic Podcast

In this episode we continue our conversation with Jan de Muijnck-Hughes a Research Associate at Glasgow University. He works using all sorts of fancy type systems mostly targeted for hardware specification, particularly with the aid of the theorem prover Idris. This episode we start by talking a little about Impostor Syndrome in academia and how he has learned to cope with it and then we dive deeper into the technicalities of his research, in particular his philosophy on Type Directed Design of Systems. We talk about Session Types, Graded Types, Quantitative types, etc. Don't forget to join our new discord channel! If you like our show please consider donating any amount at ko-fi. Links Jan's website Jan's twitter Jan's mastodon Writing and Speaking with Style Artifact Eval Andrej Bauer: Formalising Invisible Mathematics Hedy language (Felienne Hermans) Hermans' Inaugural Lecture on making PL human and inclusive Epistemic Injustice Richard Eisenberg interview 'Software Foundations' but in Agda 'System F for Fun & Profit' Reviewing Project Pages https://dsbd-appcontrol.github.io/ https://border-patrol.github.io/ Cool People Rachit Nigam Clement Pit-Claudel Software Idris Language Biblio

In this episode we have a deep conversation with Jan de Muijnck-Hughes, talks about all the cool research he has done with idris, hardware and different kinds of interesting type systems such as session types, quantitative types and graded types. In the second half we discuss all the different kinds of problems that has been going on in PL academia lately and what we can do as a community to address those issues. Also, we have a discord channel now, join us! If you like our show please consider donating any amount at ko-fi. Errata: Jan mentions 'Jeff Foster' when, in fact, he meant Nate Foster This is the SIGCOMM 'Call': https://sigcomm.quest/ Felinne Hermans did her PhD at Eindhoven and not Delft Links Jan's website Jan's twitter Jan's mastodon Writing and Speaking with Style Artifact Eval Andrej Bauer: Formalising Invisible Mathematics Hedy language (Felienne Hermans) Hermans' Inaugural Lecture on making PL human and inclusive Epistemic Injustice Richard Eisenberg interview 'Software Foundations' but in Agda 'System F for Fun & Profit' Reviewing Project Pages https://dsbd-appcontrol.github.io/ https://border-patrol.github.io/ Cool People Rachit Nigam Clement Pit-Claudel Software Idris Language Biblio

In this episode we have over Dan Plyukhin, a PhD Candidate from the University of Illinois Urbana-Champaign. We talk about Dan’s research is in the field of parallelism, more specifically garbage collection in the presence of actors. Then we also talk about Pedro's research on translating GADTs from OCaml to Coq, and the burnout process that lead him to take 10 months off from his PhD to be with his family back in Brazil. Links Dan's Personal Website Twitter: @dplyukhn

Jimmy Koppel, got his PhD at MIT and found the Mirdin Company, where he teaches engineers to write better code! In this interview we talk about how to make better code, how the knowledge of computer science theory and programming languages can help engineers to achieve that, and much more! Links Jimmy's Personal Website Jimmy's Twitter Mirdin's Website Jimmy's Blog Lastest blog post One CFG-Generator to Rule Them All Automatically Deriving Control-Flow Graph Generators from Operational Semantics Thiel Fellowship Newsletters discussed in the show Mirdin's Newsletter Hillel Wayne's Newsletter Eric Normand's Newsletter Jeremy Kun's Newsletter

In this episode we host another company that does formal method in the context of the Everscale Blockchain, and Solidity smart contracts. How and why they use formal methods in this context? Who are their clients? What are the caveats? Links Pruvendo's Website Pruvendo's Linkdin Pruvendo's Twitter

In this episode talk with Gerwin Klein about the formal verification of the microkernel seL4 which was done using Isabelle at NICTA / Data61 in Australia. We also talk a little about his PhD Project veryfing a piece of the Java Virtual Machine. Links Gerwin's Twitter Gerwin's Website ProofCraft's Website

Kevin Buzzard has been very passionate spreading the word among mathematicians to use theorem provers mechanize theorems of modern mathematics. In this conversation we will talk about his vision in teaching undergrads to use the Lean theorem prover, what is the Xena Project, his view of how theorem provers can change the way we do mathematics, and much more! Links Xena's Project Twitter Xena Project's Website Lean's Website

In this episode we partner with Formal Land, a company that works in formally verifying the Tezos codebase! I have worked with them in the past developing new features to their source-to-source compiler CoqOfOcaml. In this episode we talk about their work with Tezos and how their techniques are applicable to other codebases as well! For this we talk with Formal Land founder Guillaume Claret and the proof engineers Daniel Hilst and Pierre Vial. Links Formal Land Website Formal Land Email: contact@formal.land Formal Land Twitter: @LandFooBar CoqOfOcaml The DAO hack

In this episode we interview Lawrence Paulson, one of the creating fathers of Isabelle. We talk about the development process, how it drew inspirations and ideas from LCF and Boyer Moore. What tools were used, it’s strenghts and weaknesses, and all about the historical context at the time! We also briefly talk about his formalization of the Gödel's Incompletenes theorems in Isabelle Paulson have quite an extensive CV, he is a professor at Cambridge, have published more than 100 papers, is an ACM fellow since 2008, is a member of the royal society since 2017, among many other things! Links Larry's Website Larry's Twitter Larry's Blog

In this episode we talk about Sigplan, the organization behind the most important conferences and proceedings in our field. What is the SIGPLAN? What exactly does it do? How is it organized? How are things published? To answer these and many other questions we talk with Jens Palsberg, a professor at UCLA, who is the past chair of the SIGPLAN. And also Jonathan Aldrich, a professor at the CMU, who is a member of the ACM publication board. Links Jen's Website Jonathan's Website Jonathan's Twitter Sigplan Blog Post on Hybrid Conferences SIGPlAN-M Mentoring Program

In this episode Cody Roux teaches some interesting concepts that people care about in Mathematics and Logic as a way to try to understand what is going on in the universe around us! In particular we will try to explain concepts such as Impredicativity, Excluded Middle, Group Theory, Model Theory, Kripke Models, Realizability, The Markov Principle, Cut Elimination, and other stuff! Links Cody's website Cody's dblp

In this episode Conal Elliott gives a more concrete presentation on what is Denotational Design is and how to use it in practice. It is a continuation of episode #17, in which we had an in-depth philosophical conversation to explain why he believes that Denotational Design is a superior form of reasoning in the realm of computer science. We also continue a discussion raised by Dan Ghica on the last episode on the need for Operational Semantics and the role of elegance in reasoning and design. Along the way we also address the questions sent by the listeners in these last episodes. Links Conal's website Play/work with Conal Conal's twitter: @conal The simple essence of automatic differentiation Compiling to categories Generic parallel functional programming Denotational design with type class morphisms Quotes "A theory appears beautiful or elegant [...] when it’s simple; in other words when it can be expressed very concisely in terms of mathematics that we’ve already learned for some other reasons." - Murray Gell-Mann, Beauty and Elegance in Physics. "In Galileo’s time, professors of philosophy and theology—the subjects were inseparable—produced grand discourses on the nature of reality, the structure of the universe, and the way the world works, all based on sophisticated metaphysical arguments. Meanwhile, Galileo measured how fast balls roll down inclined planes. How mundane! But the learned discourses, while grand, were vague. Galileo’s investigations were clear and precise. The old metaphysics never progressed, while Galileo’s work bore abundant, and at length spectacular, fruit. Galileo too cared about the big questions, but he realized that getting genuine answers requires patience and humility before the facts." - Frank Wilczek, (The Lightness of Being: Mass, Ether, and the Unification of Forces) "We must make here a clear distinction between belief and faith, because, in general practice, belief has come to mean a state of mind which is almost the opposite of faith. Belief, as I use the word here, is the insistence that the truth is what one would ‘lief’ or wish it to be. The believer will open his mind to the truth on the condition that it fits in with his preconceived ideas and wishes. Faith, on the other hand, is an unreserved opening of the mind to the truth, whatever it may turn out to be. Faith has no preconceptions; it is a plunge into the unknown. Belief clings, but faith lets go. In this sense of the word, faith is the essential virtue of science, and likewise of any religion that is not self-deception." - Alan Watts (The Wisdom of Insecurity: A Message for an Age of Anxiety)

In this episode, me and Eric Bond have a great conversation with Dan R. Ghica, a professor at Birmingham University and Director of the Programming Language Research Lab of the Huaweii Research Centre Edinburgh. We talk about his work on both institutions, which includes topics such as Category Theory, String Diagrams, and Game Semantics. We also briefly discuss the current publication process of our field and entertain some thoughts on how to make it better. Finally, we touch on more personal topics such as his views about Elegance, making an insightful counterpoint to Conal’s opinions on Denotational Semantics vs. Operational Semantics. Links Dan's Twitter: @danghica Dan's Website Job advert for Huawei positions Talks and Lectures Dan's talk on Syntactic Trinitarianism (terms, graphs, diagrams) Dan's talk on a similar, more semantics-oriented talk at TERMGRAPH Dan's OPLSS course on (denotational) game semantics Game semantics lectures Papers Paper on string diagrams and their applications to reverse automatic differentiation (long paper, part of it to appear in FSCD 2020) Paper on automatic differentiation and string diagrams Paper on effect handlers Paper on optimisation with constructive reals Paper on digital circuits and string diagrams Paper on functorial boxes for string diagrams A Game semantics paper mentioned during the conversation Decidability via game semantics Landmark paper on undecidability of observational equivalence Other Links Penrose book Book on type-level string diagrams Proof assistant for higher categories The Programming Journal Midlands Graduate School