#23 What is the SIGPLAN? - Jens Palsberg and Jonathan Aldrich Sep 24, 2022

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

#22 Impredicativity, EM, Realizability and more - Cody Roux Aug 12, 2022

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

#21 Denotational Design - Conal Elliott Aug 04, 2022

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

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)

#20 Huaweii, String Diagrams, Game Semantics - Dan R. Ghica Jun 27, 2022

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

Talks and Lectures

Papers

Links

#17 The Lost Elegance of Computation - Conal Elliott May 09, 2022

In this episode I had the pleasure to have an in-depth conversation with Conal Elliott about his life, his work, his philosophy and his many opinions about research and the current state of PL Research and how it lead him to come with the concept of Denotational Design. Conal got his PhD at CMU in the 90s under Frank Pfenning working on Higher-Order Unification, after that he has devoted his life on thinking and refining graphic computation and the tools behind it.

Links

Conal’s website
Conal’s twitter: @conal
The simple essence of automatic differentiation
Compiling to categories
Generic parallel functional programming
Denotational design with type class morphisms
Functional Images
Functional Reactive Animation
Alphabet Versus the Goddess - Leonard Shlain
The information - James Gleick
Murray Gell-Mann’s definition of beauty/elegance: “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.”
A John Backus quote (from his Turing Award lecture): “Many creative computer scientists have retreated from inventing languages to inventing tools for describing them. Unfortunately, they have been largely content to apply their elegant new tools to studying the warts and moles of existing languages. After examining the appalling type structure of conventional languages, using the elegant tools developed by Dana Scott, it is surprising that so many of us remain passively content with that structure instead of energetically searching for new ones.”

#16 Agda, K Axiom, HoTT, Rewrite Theory - Jesper Cockx Apr 02, 2022

in this episode we interview Jesper Cockx, one of the core developers on Agda. We talk about the philosophy behind Agda, his work on pattern matching, the Uniqueness of Identity of Proofs, UIP for short, and why it is inconsistent with Homotopy Type Theory.

Links

Jesper’s Website
Jesper’s Twitter: @agdakx
Jesper’s PhD Thesis
Rewrite Theory paper
Pattern matching without K paper (Check his website for more)
EuroProofNet
WITS Talks on Youtube (Workshop on the Implementation of Type Systems)
Agda Zulip
Agda Mailing List
Ataca Github
Wadler’s book on Agda
Stump’s book on Agda

#15 Coq Projects, Agda, Idris, Kind - Nitin and Eric Mar 27, 2022

In this episode me, Eric and Nitin continues our conversation started in the last episode. This time we move our attention to the cool projects happening in Coq, in particular commenting through the projects mentioned in Andrew Appel’s keynote “Coq’s Vibrant Ecosystem for verification engineering” that took place in CPP’22 which is colocated with POPL and towards the end we also talk about agda, idris and Kind.

Links

#14 POPL, Parametricity, Scala, DOT - Nitin and Eric Feb 12, 2022

In this episode I gather with two good friends Eric and Nitin to randomly talk random subjects that pops up. Among them we talked about POPL, Scala, Isabelle, Parametricity, Dependent Object Types (DOT, for short) and more!

Links

Nitin Twitter @NitinJohnRaj2
Eric Twitter @EricBond10
Collection of links on logical relations
Theorems for Free
Reynolds Paper
Practical Foundations for Programming Languages

#13 C/C++, Emacs, Haskell, and Coq. The Journey - John Wiegley Dec 23, 2021

This episode is about the journey of a programmer that converted himself into a Haskell developer after working with C/C++ for more than 10years.

Here are a few questions that you’ll find the answer to in this episode:

What does he find so compelling about Haskell?
Why did it make him dive deeper into the Theoretical Computer Science?
Why did it make him learn Coq and Category Theory?
How does Coq compare with ACL2?
How do both Coq and ACL2 compares to TLA+?
Did learning Coq make John a better programmer?

Links

John’s Email: johnw@newartisans.com
John’s Twitter: @jwiegley

#12 Tenure, Sexism and ADHD - Talia Ringer Nov 10, 2021

Talia Ringer is an Assistant Professor at University of Illinois Urbana-Champaign. She did her PhD at University of Washington with her thesis on Proof Repair.

She’s very active on twitter @taliaringer. And in this episode we will talk about her transition from PhD to Professor, her work on diversity, her ADHD and how it has affected her career so far, and we also touch on the delicate topic of sexism in academia.

Links

#11 FP, Monads, GHC, and beyond - Alejandro Serrano Oct 04, 2021

In this episode we have talk with Alejandro Serrano Mena, he works on 47 degrees and is a published author of two books about Haskell: The Book of Monads and Practical Haskell.

We talk about many interesting features behind functional programming such as adts, pattern matching, impredicativity, monads, effects, hacking the ghc and how all this comes together to grab industry attention to adopt functional programming features over the past decade.

Links

#10 Classical Logic vs Intuitionistic Logic - Thorsten Altenkirch and Anupam Das Jul 15, 2021

In this episode we host a discussion between Anupam Das and Thorsten Altenkirch on the role of constructivism in mathematics, logic and computer science.

Anupam is a lecturer in the University of Birmingham in the UK, and Thorsten Altenkirch is a CS Professor at the University of Nottingham.

We discuss why constructive content in proofs matters, the law of excluded middle, the axiom of choice, category theory, and much more!

Links

#9 Logic and Proof Theory - Anupam Das May 28, 2021

In this episode I interview Anupam Das we have a nice conversation on the historical perspective of how Logic and Proof Theory as we know today came about in the 30’s. The differences between Natural Deduction and Sequent Calculus, Cut Elimination and much more.

Links

#8 Cedille - Chris Jenkins May 10, 2021

In this episode I have a nice conversation with Chris Jenkins to talk about the Cedille theorem prover, based on a very concise type theory called CDLE. The main selling point of Cedille is that the theory is so small that the typing rules fit one page. And yet it is strong enough to do relevant theorem proving. This is probably the most technical episode so far.

Links

#7 Hacking Isabelle's Internals - Daniel Matichuk Apr 15, 2021

In this episode we dive into Isabelle, the interactive theorem prover based on Higher Order Logic directly from someone who spent quite some time hacking on its internals.

Me and Daniel also talk about Mizar, Isar, the seL4, and how it is formalized.

Torwards the end of the episode we also talk a little about his current work on the binary analysis of Aarch32 Arm Archtecture at Galois.

#6 All The Dumb Questions on Gradual Types - Zeina Migeed Mar 29, 2021

In this episode we interview Zeina Migeed, a PhD Student at University of California Los Angeles, advised by Prof. Jens Palsberg

She Researches Gradual Types and had a paper published at POPL’20 named “What is Decidable about Gradual Types”. here is a link to it

As the name of the episode suggests, I’ll be asking her all the dumb questions related to not only gradual types, but also intersection types and recursive types as well!

#5 The History of Coq'Art - Yves Bertot Feb 27, 2021

In this episode we interview Yves Bertot and we talk about the history behind his contribution with Pierre Castéran on writing Coq’Art. What is Yves’ role in the Coq Team, how the team works and what are the sort of contributions they accept.

Links:

Yves email: yves.bertot@inria.fr

Affichage et manipulation interactive de formules mathématiques dans les documents structurés - Check figure 15 for an example on how Yves’ tools would build trees internally

A video showing his tool in practice, doing proofs with mouse clicks

A Genereic Approach to Building User Interfaces for Theorem Provers

#4 Theorem Provers, Functional Programming and Companies - Eric Bond Feb 15, 2021

In this episode we host Eric Bond to go through some real cool projects happening in the PL World and some of the companies behind them.

We discuss some technical differences between the major interactive theorem provers out there, some of their most popular projects, and a few companies that work in the realm.

Eric Bond works at 47 degrees, a consulting company on Functional Programming Languages, specially on Scala and Haskell. You can find Eric @ericbond10 on Twitter.

During the episode we mention PL Talks and the Midlands Graduate School in the Foundations of Computing Science 2021.