Incremental computation and the web

I’ve recently been thinking about the world of JavaScript and web applications. That’s odd for me, since I know almost nothing about the web. Indeed,...

Why OCaml?

Testing with expectations

Testing is important, and it’s hard to get people to do as much of it as they should. Testing tools matter because the smoother the...

Quickcheck for Core

Automated testing is a powerful tool for finding bugs and specifying correctness properties of code. Haskell’s Quickcheck library is the most well-known automated testing library,...

rsync rounds timestamps to the nearest second

I’m not sure how I’ve managed to use rsync for so many years without ever noticing this, but hey, you learn something new every day!...

No (functional) experience required

Jane Street is a serious functional programming shop. We use OCaml, a statically typed functional language for almost everything and have what is probably the...

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Introducing Incremental

I’m pleased to announce the release of Incremental (well commented mli here), a powerful library for building self-adjusting computations, i.e., computations that can be updated...

Converting a code base from camlp4 to ppx

As with many projects in the OCaml world, at Jane Street we have been working on migrating from camlp4 to ppx. After having developed equivalent...

CPU Registers and OCaml

Even though registers are a low-level CPU concept, having some knowledge about them can help write faster code. Simply put, a CPU register is a...

Reverse web proxy in ~50 lines of BASH

In the spirit of reinventing the wheel for fun, I hacked this together as a quick challenge to myself last week. It’s a little rough...

Building a lower-latency GC

We’ve been doing a bunch of work recently on improving the responsiveness of OCaml’s garbage collector. I thought it would be worth discussing these developments...

Faster OCaml to C calls

The official OCaml documentation “Interfacing C with OCaml” doesn’t document some interesting performance features.

Why GADTs matter for performance

When GADTs (Generalized Algebraic Data Types) landed in OCaml, I wasn’t particularly happy about it. I assumed that it was the kind of nonsense you...

A lighter Core

We recently released a version of our open source libraries with a much anticipated change – Async_kernel, the heart of the Async concurrent programming library,...

Centralizing distributed version control, revisited

7 years ago, I wrote a blog post about how we at Jane Street were using our distributed version control system (hg, though the story...

Making making better

We spend a lot of time and effort on training new people, and it never stops for long. Right now our winter-intern class is ending;...

13 Virtues

Very early on in his life, while on lengthy voyage from London to Philadelphia, Ben Franklin created a system of thirteen virtues to live his...

Inspecting the Environment of a Running Process

Sometimes its useful to be able see the values of environment variables in running processes. We can use the following test program to see how...