The OCaml Planet

OCaml is famous for allow you to do a lot of things like modules. Like really a lot! Advanced features like functors, aside, it’s really common to either alias module names to something shorter or localize open Module_name to a smaller scope:

In my previous article I mentioned that OCaml’s Stdlib leaves a lot to be desire when it comes to regular expressions. One thing I didn’t discuss back then was that the problem is somewhat mitigated by the excellent module Scanf, which makes it easy to parse structured data.

One of the things that bothered me initially in OCaml was the poor support for working in regular expressions in the standard library. Technically speaking, there’s no support for them at all!

Jane Street is a trading firm that uses a variety of high-performance systems built in OCaml to provide liquidity to financial markets worldwide. Over the last couple of years, we have started developing major extensions to OCaml’s type system, with the primary goal of making OCaml a better language for writing high-performance systems. In this talk, we will attempt to provide a developer's-eye view of these changes. We’ll cover two major directions of innovation: first, the addition of modal types to OCaml, which opens up a variety of ambitious features, like memory-safe stack-allocation; type-level tracking of effects, and data-race freedom guarantees for multicore code. The second is the addition of a kind system to OCaml, which provides more control over the representation of memory, in particular allowing for structured data to be represented in a cache-and-prefetch-friendly tabular form. Together, these features pull together some of the most important features for writing high performance code in Rust, while maintaining the relative simplicity of programming in OCaml. In all of this, we will focus less on the type theory, and more on how these features are surfaced to users, the practical problems that they help us solve, and the place in the design space of programming languages that this leaves us in.

Our sister company Parsimoni sends OCaml into space aboard DPhi Space's Clustergate ride-sharing platform to test the cababilities of SpaceOS.

Some titles make more sense than others. One of my oldest contributions to OCaml was a complete overhaul of Unix.stat et al in ocaml/ocaml#462 which formed part of OCaml 4.03. As part of the work on msvs-detect in late 2015, I’d ended up with a Windows 7 VM which had every single version of Visual Studio back to Visual Studio 6.0. Visual Studio (and Visual C++ before that) has always included the source code for the C Runtime Library (CRT), and as a side-effect of having all these installed Visual Studios, I was able to construct a Git repository showing the evolution of the CRT code over each release (sadly, the licence doesn’t allow this to be pushed publicly). This was particularly useful for studying how the behaviour of the stat implementation had changed over time, particularly with reference to Windows Vista’s symlinks. Anyway, that particular bit of work left me with a habit of often reaching for the CRT whenever something weird’s happening, and that’s led naturally to a fairly detailed bug-fix - and outline for more bug-fixes - in OCaml.