My first day at Penn, the Schuylkill flooded 16ft because of Hurricane Ida, and classes were cancelled. I'm starting my new job on Monday, and so of course New York is expecting the largest blizzard in over a decade

The next iteration of NJPLS will be held at the University of Pennsylvania on 22 May 2026! If you'd like to attend or submit a talk proposal, check out the website for details: njpls.org/may2026.html

Seems like a good time as any to say I'm: (1) moving to New York next week, where I'll: (2) be writing OxCaml at Jane Street! Excited to start the next thing :)

Successfully defended my dissertation today. Now Dr. Joe!

Still OCaml

Hey, I'm looking for speakers at DC Systems for this year! Let me know if you, or anyone you know would enjoy giving a talk to an extremely nice and curious audience!

It’s called ‘vs code’ because the code is an enemy you are fighting

also, Applicative usually being defined in terms of (<*>) and not liftA2 was so incredibly damaging.

They’re killing people as a twitter joke. It’s depraved. Can’t let yourself lose the capacity to be appalled and disgusted and outraged by this.

Considering hiding some ancient PL twitter memes deep in my dissertation

Every time I have something important to do, I start a new side project. Instead of writing my dissertation, I spent the last few days optimizing an OxCaml implementation of the One Billion Row Challenge (1brc). I'd much rather write about this!! Oh well, maybe after I'm done dissertating.

Is there ever a reason to explicitly copy a file into memory instead of mmapping it if you don't plan to write it?

I have also experienced this. When it works well (not always), Claude code can free me up to think mostly about the bits of the work I'm interested in.

I will also be at ICFP/SPLASH in Singapore! Similarly excited to see everyone (especially Harry)

I'm very excited about this new movie from Kathryn Bigelow. More great movies about how terrifying nukes are can only be a good thing. Side-bonus: I expect more WIRED videos featuring @wellerstein.bsky.social www.youtube.com/watch?v=_wpw...

Have you been considering hosting a local PL meetup? Need a good place to start? Check out the PL Perspectives post that I wrote with Michael Greenberg and Noam Zilberstein! blog.sigplan.org/2025/09/16/think-globally-discuss-pl-locally/

Upstate NY folks: Cornell will be hosting Upstate PL (www.cs.cornell.edu/upstate-pl/) on Thursday, August 28th. You should come if you're in the area! Talk proposals are due August 4th, registration closes August 18th.

Some more exciting news! This year we had not one, but two(!) dissertations receiving the SIGPLAN John C. Reynolds Doctoral Dissertation Award at PLDI! The awardees are: Harrison Goldstein from the University of Pennsylvania and Rachit Nigam from Cornell University. More info ⬇️

Reality has a well-known liberal bias

Headed to NYC for the summer! If you're in town and want to hang out, let me know!

Going to New York on Saturday morning. Tomorrow will be spent feverishly packing and being a little ball of excitement

Passed my proposal defense! Now a PhD candidate, I guess.

There is a false dichotomy drawn between "the ivory tower" and "the real world," and I'm here to report that in a post-industrial society, your real-world economy absolutely hinges on the university. University towns are factory towns. Universities drive economic activity, not the other way around.

Wow, they made Cheyenne Mountain from the hit 1983 thriller WarGames starting Ally Sheedy and Matthew Broderick into a real place!

It’s genuinely embarrassing that people keep falling for these “AI explains the hidden secrets of its programming” posts. Grok is not sentient, it cannot explain what it’s doing and why.

On the way back to Philly after an exhausting week in NYC. One week at home, then to Colorado for my brother’s college graduation. Then back to Philly to propose my thesis, then to NYC for the summer!

If you are considering applying for a PhD this Fall, please get in touch. I’m looking for students who are interested in PL, SE, and/or HCI — and ideally all three! You can find more information about me and my work on my website: harrisongoldste.in

I'm incredibly excited to announce that I've accepted a tenure-track position as an assistant professor at the University at Buffalo! The PL/SE group at UB is already really impressive, and I am honored to be part of its continued growth

Ok, I put up this little library SubSlice for per-index refcounted access to a slice on Github. Maybe it'll be useful for someone someday, who knows. github.com/alpha-conver...

Rust-knowers. Is there a good way of getting RefCell-like refcounted access to disjoint slices of an array? Essentially, this, but with a (presumably) less dumb implementation of the reference counting structure. gist.github.com/alpha-conver...

Academic labs train people up from scratch while doing research. And then when a researcher is at their most productive, we kick them out and start over from scratch. Federal government grants cover the costs of most PhD student training. It a public good that makes US companies ultra-competitive…

Honored to be honorably mentioned for the Jane Street Grad Fellowship! PL is well-represented on this list :) www.janestreet.com/join-jane-st...

ALL TRUMP HAS TO DO IS SNAP HIS FINGERS I wrote about what we could go back to if Trump just snapped his fingers right now. Sub to the Odd Lots newsletter right here: www.bloomberg.com/account/news...

Been spending a lot of time recently playing around in Rust. I've found @jonhoo.eu's book absolutely invaluable. It may as well be titled "Rust for PL People"

I recently got a paper subscription to WIRED, after being really impressed by some of their reporting on DOGE. I last had a WIRED subscription when I was ~13. Back then it was almost entirely about consumer electronics and gadgetry. Now every article is about software.

Been watching The Pitt recently on HBO. Really exceptional for a medical drama.

Say I have an ML-like language. If I want to be able to monomorphize, what do I need to rule out? Certainly polymorphic recursion, but what else?

Ok time to learn Rust. Yes, for real this time. No I won't get distracted by some Haskell nonsense and bounce off it again. Yes, I promise. Totally.

One of my favorite activities is introducing people to Tom7's videos

We're about to submit the coolest paper I've ever worked on and I'm so damn excited about it. I can't wait til it gets in somewhere so we can talk about it.

New profile picture just dropped

Every time I have a background check for a job I get all anxious. "What if I actually completely hallucinated that time I worked at AWS?"

Use labeled arguments, in OCaml!! If your function takes two arguments of the same type, please don't make me remember which one is which.

When, exactly, does the ocaml GC run? And moreover, if I mark an external function as noalloc, does this guarantee that the GC will not run during it?

This is the greatest programming project of all time www.youtube.com/watch?v=0mCs...

New paper: Simulating Time With Square-Root Space people.csail.mit.edu/rrw/time-vs-... It's still hard for me to believe it myself, but I seem to have shown that TIME[t] is contained in SPACE[sqrt{t log t}]. To appear in STOC. Comments are very welcome!

Oops, I over-functorized my OCaml code again