mgreenblog

Along with the PaSh folks, I have two closely related papers at OSDI 2026: one about try and one about hs, which uses try extensively.

We (me, Konstantinos Kallas, Nikos Vasilakis, and Vagos Lamprou) gave a tutorial at POPL 2026 on the POSIX shell: Recent years have seen a resurgence of research on the shell, from optimizing scripts to better leverage parallel and distributed computation…

Following a mysterious and generous invitation from Kristopher Micinski, four computer scientists (Annie Liu, Frank McSherry, Scott Stoller, and me) drove into deep upstate New York.

I frequently start interactive programs from a terminal---often using the handy xdg-open script, sometimes explicitly.

I spoke at PLMW 2025, giving a talk titled "How to give a good talk".

I am a technical consultant for Materialize---a database for integrating and transforming real-time data---and I just blogged for them about some of the work I've been doing there: Source Mapping and Introspection: Debugging Materialize with Materialize M…

I finally converted my old blog, weaselhat.com to a static site.

I’m looking for PhD students in the Fall 2023 application cycle, to start in Fall 2024.

The first person to explain answer set programming (ASP, pronounced ‘ay ess pee’) to me (Joe Osborn) told me about the three line implementation of graph coloring and the termination guarantees.

Part of what’s hard about grad school is that things are undirected.

Program synthesis is an appealing notion: I give you a pretty good (but incomplete) description of a program, and you give me a working program back out.

Kleene algebra with tests is a beautiful, powerful framework for reasoning about programs.

How should we summarize performance numbers?

I want to believe in a future where the lion will lie down with the lamb; we'll beat our swords into plowshares; and developers will migrate dynamic prototypes to robust static systems with confidence.

I'm looking for PhD students in the Fall 2021 application cycle, to start in Fall 2022.

After six years at Pomona College, I've moved to Stevens Institute of Technology as an assistant professor in the computer science department.

Pomona College's computer science department is hiring Fall of 2021 for Fall 2022.

The Unix shell is incredibly powerful.

I have a new post up on the SIGPLAN blog: "Making PL Ideas Accessible: An Open-Source, Open-Access, Interactive Journal.

POPL 2021 is open for business on Clowdr!

I recently wrote on the SIGPLAN blog about how PL notation is a barrier to entry.

Robin Gandy's "On the Axiom of Extensionality--Part 1", Journal of Symbolic Logic, Vol. 21, No. 1 (Mar., 1956) quotes Alan Turing using a racist phrase.

So you want to define a gradual type system, like all the cool kids?

If you read a description of a static analysis in a paper, what might you find?

When I mentioned how important smart constructors are for Brzozowski derivatives on Twitter, when Prabhakar Ragde raised an interesting question about how big the derivative of a regex is.

CS 181-N Advanced Functional Programming is a project-based elective I'm teaching this semester.

Shriram Krishnamurthi, Arjun Guha, Leo Meyerovich, and I wrote a post about Flapjax on PL Perspectives, the SIGPLAN blog.

I've been building an executable formalization of the POSIX shell semantics, which I've been calling smoosh (the Symbolic, Mechanized, Observable, Operational SHell).

The recent organizers of the Off the Beaten Track (OBT) workshop (Luke Church, Bob Atkey, Lindsey Kuper, Swarat Chaudhuri, Ranjit Jhala, Shriram Krishnamurthi, David Walker, and me) have decided not to hold OBT at POPL 2020.

I'll be presenting my thoughts on the state of gradual typing research---along with some goals and challenges---at SNAPL 2019.

While on sabbatical in Cambridge, MA (thanks, Steve!)

I've been thinking about and working on the POSIX shell for a little bit over a year now.

NB I left Pomona college in 2021.

I recently gave a talk to some Pomona College undergrads about how to secure their various devices (computers and phones in particular).

Per a request of sk19er on the Wordpress forums, I've implemented a new feature for PHPEnkoder: you can use the [noenkode] shortcode to turn off PHPEnkoder on a specific page.

In hybrid type checking, a subtyping relationship between subset types {x:T|e} determines when it's safe to omit a cast.

I recently had some trouble getting ctypes working, so I thought I'd share my solution.

Frank Pfenning originated the idea of refinement types in his seminal PLDI 1991 paper with Tim Freeman.

I'm working on a Twitter bot, and I ran up against something very annoying: apps need to be on an account with a mobile phone number.

I've resolved some E_NOTICE-level messages that were showing up when people set WP_DEBUG to true.

As an academic computer scientist, I frequently interact with the world of 'tech', as embodied by Silicon Valley, startups, etc.

I'm really happy to be part of the first PLVNET, a workshop on the intersection of PL, verification, and networking.

I am delighted to announce that Space-Efficient Manifest Contracts will appear at POPL 2015 in Mumbai.

Reading Aseem Rastogi, Avik Chaudhuri, and Basil Hosmer's POPL 2012 paper The Ins and Outs of Gradual Type Inference, I ran across a quote that could well appear directly in my POPL 2015 paper, Space-Efficient Manifest Contracts: The key insight is that .…

I recently wrote a bit of code for scheduling the discussion order of PC meetings so as to minimize traffic in and out of the room due to conflicts of interest.

I have a new and much improved draft of my work on Space-Efficient Manifest Contracts.

Cole Schlesinger, Dave Walker, and I submitted a paper to ICFP 2014.

I just finished reading A Balance of Power: Expressive, Analyzable Controller Programming.

I've released a bugfix for PHPEnkoder version 1.12.

I'm really delighted to have resolved a longstanding problem with PHPEnkoder and Unicode: PHPEnkoder should no longer choke on the various multi-byte characters, such as λ and è and ワ.