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David Allsopp

@dra27.uk
249 followers 60 following 80 posts

Cambridge-based, London-working software engineer; sometime classical singer. @dra27 in many places, including GitHub; OCaml maintainer; opam maintainer; Windows {apolog,evangel}ist

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David Allsopp @dra27.uk · 26/07/2026
“Daddy, your code is amazing” - inspiring future generations (in Scratch 🫣🤫🤐)
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David Allsopp @dra27.uk · 06/07/2026
Hopelessly nerd-sniped by github.com/ocaml/ocaml/... … continuing a fine Jane Street tradition of surfacing kernel bugs using OCaml - just not in our usual kernel!
github.com
OCaml 5.5.0 build failure on Windows · Issue #14871 · ocaml/ocaml
The attempt to upgrade my Windows OCaml installation to 5.5.0 keeps failing, please see the following log. The path C:\\Users\\me\\AppData\\Local\\opam\\default\\lib\\toplevel:stdlib.cmi that it tr...
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David Allsopp @dra27.uk · 02/04/2026
#tgiÞ
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David Allsopp @dra27.uk · 15/03/2026
Doing some clearing out - do these belong in recycling… or in a museum? 😂🤔
Photograph of two interoffice mailing envelopes
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David Allsopp @dra27.uk · 10/03/2026
Seeing the news of Moltbook’s “acquisition” is somehow making me want to (re-)watch Memento 🤔
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David Allsopp @dra27.uk · 06/02/2026
_Great_ Northern; _Great_er Anglia; _Great_ Western Railway; Thames_link_ … all ironies of naming 🤔
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David Allsopp @dra27.uk · 26/01/2026
Claude Code has committed in trunk OCaml! With great power comes great responsibility, and all that...
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David Allsopp @dra27.uk · 07/01/2026
Fantastic special series of episodes of @timharford.ft.com and co’s More or Less occupying the BBC Radio 4 9am slot *every day* this week
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David Allsopp @dra27.uk · 04/01/2026
I was implicitly referred to as a “hoary greybeard” the other day… my son just innocently asked how long I’ve worked on/in OCaml and I realised the answer is half my life 👴🏻 #old #greybeard
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David Allsopp @dra27.uk · 17/12/2025
It’s merged!! 🥳🥳🥳
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David Allsopp @dra27.uk · 30/11/2025
Haven’t had to use a paper train ticket in a looong time, and was somewhat bemused to see the machine list that it would be printing two seat reservations. I am duly sat in my first non-specific seat of the day. Nice paper-saving there, @greateranglia.bsky.social!
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David Allsopp @dra27.uk · 29/11/2025
Aaaand, breathe again… 😮‍💨 github.com/ocaml/ocaml/...
github.com
Relocatable OCaml - `--with-relative-libdir` by dra27 · Pull Request #14244 · ocaml/ocaml
This is the second of three PRs which implement Relocatable OCaml as proposed in ocaml/RFCs#53. The series of changes in this PR combine to allow the absolute location of the Standard Library (e.g....
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David Allsopp @dra27.uk · 25/11/2025
There are some minor corrections to be made in each branch, but Relocatable OCaml has passed its defence!
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David Allsopp @dra27.uk · 08/11/2025
Being British, I’m of course able to read this both negatively and positively 🫢 news.ycombinator.com/item?id=4585...
news.ycombinator.com
Opam on Windows is a masterpiece of engineering | Hacker News
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David Allsopp @dra27.uk · 05/10/2025
Unsure whether to be more shocked by the discovery that there will be 10 current/former lay clerks singing at this morning’s mass at Westminster Cathedral (first time for a decade?) or that they’ve completely renovated the 100 year old song school toilets!
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David Allsopp @dra27.uk · 23/09/2025
Quite an extreme case of rewrite-it-in-Rust… www.nature.com/articles/d41...
nature.com
The Moon is rusting — thanks to ‘wind’ blown all the way from Earth
Lunar minerals generate the rust mineral hematite when bombarded with high-energy oxygen particles, experiments show.
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David Allsopp @dra27.uk · 15/09/2025
3 years since I finalised the demo of it for the OCaml Workshop in Ljubljana, Relocatable OCaml is finally submitted for review! 🥳🍾🎊
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David Allsopp @dra27.uk · 29/08/2025
Currently dotting ‘i’s and crossing ‘t’s and therefore wishing I’d used fewer ‘i’s and ‘t’s in my code (also, when I did I start handwriting code?? 🤔) #relocatable #ocaml
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David Allsopp @dra27.uk · 27/08/2025
Reeling in shock and awe at just how simple and fast live-moving VM storage is in Hyper-V #scarred-by-esxi
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David Allsopp @dra27.uk · 17/08/2025
Wonders how much water Apple could save each year by having Apple Mail offer to reduce the size of photos being emailed from an iPad in the same way as it does on an iPhone? 🤔🧐🤫
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David Allsopp @dra27.uk · 15/08/2025
Remembering the grandfather who could not forgive so that hopefully we might learn from it #VJ80
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David Allsopp @dra27.uk · 12/08/2025
“I do not know whether there is anything peculiarly exciting in the air of this particular part of Hertfordshire, but the number of engagements that go on seems to me considerably above the proper average that statistics have laid down for our guidance.” Good old Oscar 🤣
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David Allsopp @dra27.uk · 04/08/2025
Congratulations to Apple for anticlimax of the month with Apple “Intelligence”. In a metaphor for the age, seems all the time has been spent on the animations and hype and not a lot on it actually doing anything 🤷🏻‍♂️ #unabletosummarisethismessage
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Reposted by David Allsopp
Yaron Minsky @yminsky.bsky.social · 21/07/2025
Yet another small OCaml/OxCaml diff has been squished! Polymorphic parameters has just gotten merged upstream: github.com/ocaml/ocaml/... There's more to go (include functor, for example: github.com/ocaml/RFCs/p...), but it's nice to see more progress in this space.
github.com
Polymorphic Parameters by voodoos · Pull Request #13806 · ocaml/ocaml
This upstreaming PR adds the possibility to have function parameters with polymorphic types in the language. This work was originally done by @lpw25 in Jane Street's fork of the compiler with e...
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David Allsopp @dra27.uk · 20/07/2025
Testing opam packages for Relocatable OCaml which actually take advantage of it. Creating a new switch using the same version as one you've already built in another switch now takes 5 seconds, rather than 2 minutes (cloning the compiler itself takes just 100ms of that 5 seconds!)
Terminal screenshot showing an existing opam switch being cloned in under 5 seconds on Linux, with the new compiler reporting its new location
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David Allsopp @dra27.uk · 17/07/2025
Is it late enough in the day to be allowed to acknowledge the #oxcaml themed Wordle?
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David Allsopp @dra27.uk · 02/07/2025
Some very strong resonances for me (with thanks to @chshersh.com for drawing into my view over on X…)
youtube.com
Keynote: Rethinking our Adoption Strategy - Evan Czaplicki | Lambda Days 2025
YouTube video by Code Sync
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David Allsopp @dra27.uk · 01/07/2025
Childishly amused that the journey from Cambridge to Newcastle begins with a train to Liverpool #weregoingthewrongway
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Reposted by David Allsopp
Yaron Minsky @yminsky.bsky.social · 13/06/2025
I'm pleased to announce OxCaml! OxCaml is Jane Street's branch of OCaml. We've given it a new name and a snazzy logo, and done a bunch of work to make it easy for people to try.
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David Allsopp @dra27.uk · 01/06/2025
1994 (and earlier): select text in one “app”, copy, paste to another “app” 2025: select text in one app, copy, switch to other app and discover they’ve disabled paste on the input fields. Return to other app. Write information on piece of paper. Type into other app. #progress #modern
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David Allsopp @dra27.uk · 13/05/2025
Oh my goodness! 😳 #wato #bbcr4
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David Allsopp @dra27.uk · 18/04/2025
Fell through a wormhole and sang the Solemn Passion + traditional Tallis Lamentations at Westminster Cathedral today. Realised the last time I did that was 17 years ago 🥺😳👴🏻
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The Register @theregister.com · 16/04/2025
Uncle Sam abruptly turns off funding for CVE program. Yes, that CVE program
dlvr.it
Uncle Sam abruptly turns off funding for CVE program. Yes, that CVE program
Because vulnerability management has nothing to do with national security, right? US government funding for the world's CVE program – the centralized Common Vulnerabilities and Exposures database of product security flaws – ends Wednesday.…
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David Allsopp @dra27.uk · 16/04/2025
Wondering if this is a judging stare about the delays getting Relocatable OCaml’s first pull request opened, or possibly something else… 🐈‍⬛ #catcaml
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David Allsopp @dra27.uk · 07/04/2025
Possibly using them gratuitously, but I’m liking OCaml 5.4’s labelled tuples for logic setting up predicates. Nice to avoid stuff like let p1, p2, (* … *) = if (* something *) then (true, false, false, true, true) else if (* … *) but without the weight of having to declare a record #ocaml
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David Allsopp @dra27.uk · 01/04/2025
This is not an April Fool! #IYKYK #ocaml
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Reposted by David Allsopp
Anil Madhavapeddy @anil.recoil.org · 29/03/2025
uh oh AI safety meets OCaml and the seatbelts have come off real fast
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David Allsopp @dra27.uk · 27/03/2025
Initial idea - July 2019 Design proposal (before any code! 😇) - November 2019 Initial prototype - September 2021 Working prototype - September 2022 Candidate implementation - April 2025 #RAD 🫣
github.com
Relocatable OCaml by dra27 · Pull Request #53 · ocaml/RFCs
Rendered version. The first proof-of-concept of this work was presented at OCaml Workshop 2022. The OCaml compiler distribution requires the Standard Library to be stored in a fixed location, speci...
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David Allsopp @dra27.uk · 05/03/2025
Always check what Copilot’s doing 😜
bbc.co.uk
Paddy Power High Court case: Gardener wins £1m payout
Corrine Durber was told her jackpot was a computer error, but a judge ruled in her favour.
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David Allsopp @dra27.uk · 01/03/2025
Finally - Relocatable OCaml in “fully relocatable” mode is also reproducible (as long as the C compiler is reproducible) and passes its testsuite 😮‍💨🥳🎉🍾🎊
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David Allsopp @dra27.uk · 08/02/2025
Love this - especially the last line 😂 - but particularly because while doing something else in the OCaml runtime this week, I did scroll by and briefly pause on one of the (doubly) linked lists in the runtime’s memory allocator 🥸🤣
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David Allsopp @dra27.uk · 17/01/2025
PostScript 😂😁
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David Allsopp @dra27.uk · 16/01/2025
Encountered printf-debugging? Today I raise you "ls -l"-debugging 😂
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David Allsopp @dra27.uk · 09/01/2025
OCaml 5.3.0 is out discuss.ocaml.org/t/ocaml-5-3-...! Thanks to the considerable efforts of my colleagues, it includes the restored MSVC port (the draft was my Christmas 2022 OCaml hacking). Hopefully 5.4.0 will conclude another 2021/22 bit of hacking with Relocatable OCaml and faster opam switches!
discuss.ocaml.org
OCaml 5.3.0 released
We have the pleasure of announcing the release of OCaml version 5.3.0. dedicated to the memory of John William Mauchly and Paul Verlaine on the anniversary of their death. De la musique avant tout...
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David Allsopp @dra27.uk · 31/12/2024
Woah 🤯🔥☄️ Surface Pro X (Microsoft SQ2; Oct 2020) vs Surface Laptop 7 (Snapdragon X Elite; Jun 2024): ➡️ configure tree — 69s vs 28s (loads of x64 emulation) ➡️ make -j — 6:44 vs 2:42 ➡️ make -C testsuite parallel — 14:19 vs 4:35 (almost pure ARM64)
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David Allsopp @dra27.uk · 31/12/2024
Turns out `raise Not_found;;` touches nearly all the required corners, but that’s natdynlink now fully working and the entire testsuite passing. Started working on a Windows-on-Arm OCaml prototype in September 2020 - just over 4 years to get it finished is pretty good for my track record 😜😁 #ocaml
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David Allsopp @dra27.uk · 31/12/2024
Entered `let x = 42;;` and finally received the response `val x : int = 42` instead of a segfault 🥳 🤓 #arm64 #windows
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David Allsopp @dra27.uk · 12/12/2024
How can we be at 8 issues of the open group standard base specifications and there still isn’t a portable *simple* way to get from, say “false” to “/usr/bin/false”?
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Marcin Krzyzanowski @krzyzanowskim.com · 03/12/2024
as a kid, i fixed my parent's computer. as an adult I fix my kids's computer. pretty sure we are the only gen that knows how computers work
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Reposted by David Allsopp
Susie Dent @susiedentwords.bsky.social · 18/11/2024
Word of this morning is ‘procaffeinate’: to put everything on hold until you’ve had sufficient amounts of coffee.
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