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Effective ML

Jane Street
Lectures
YouTube
2 HN users recommended this lecture2 months2018–2021 score 2.5
Years with an HN recommendation, 2007–2026

It is the go-to source for the idea of making illegal states unrepresentable through types, with the key moment at 28:02.

Yaron Minsky of Jane Street gave this talk to Harvard's OCaml-based CS51 class in 2010. It collects advice on being an effective ML programmer in an industrial setting.

“Richard Feldman dives deeper into the topic with a lot more examples in” (HN, 2018)

1 strong recommendations · 1 recommendations · 1 citations · Lectures · intermediate

3 Hacker News comments

From the HN archive; up to 20 kept per video, favoring different commenters. Recommendations first.

@jasim Nov 2018 Strongly recommends
on HN thread Book Review: A Philosophy of Software Design
That'll be a great addition to the book. Can I also recommend Yaron Minsky's talk on OCaml, specifically the part where he talks about "making invalid states impossible": [this video] I've found this to be the single most valuable programming technique I've learnt. Richard Feldman dives deeper into the topic with a lot more examples in [link]
Minsky on making invalid states impossible
@chillee Feb 2018 Recommends
on HN thread What Made Lisp Different (2002)
I guess the closest thing to what you want in Ocaml is modular implicits. [link] As far as the tradeoff, my view on types is a bit different than yours, I think. First, a quick note: > specify manually all the types of all the functions This is usually encouraged in OCaml, in the form of a .mli file. I think types can be a lot more than "compiler checked documentation that can also work as basic tests". They allow you to encode invariants that allow the compiler to check more than basic stuff. I thought this video had a good example. [this video]
Good example of encoding invariants in types

Citations, criticism and jokes

@marshray Nov 2021 Cites it
on HN thread Why Co–Star Uses Haskell
"Make illegal states unrepresentable" is usually attributed to Yaron Minsky of Jane Street. This video shows it at 28:02. [link] [this video]
Source of 'make illegal states unrepresentable' at 28:02

Video list and Hacker News comment labels from HackerTube (prompted by @karpathy), released under ODC-By 1.0, built on the open-index/hacker-news archive. Hacker News data is provided by Y Combinator; comments remain the work of their authors. Video titles, channel names and thumbnails belong to their creators and are shown via YouTube. HackerTube Watch is an unofficial edition. Data export of 2026-10-31.

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