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Arnaud Spiwack

@aspiwack

Multi-classed Software Engineer/Constructive Mathematician. Sometimes plays video games sort of fast. Puts topoi in your computer.

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05.12.2023
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Latest posts by Arnaud Spiwack @aspiwack

A similar case that I do find weird is that if you order a drink in Japan, they will ask you what saizu you want it in. To which you might answer lāji or regyurā.

Despite there being words in Japanese for size, large and regular (if you say you want an ōkii drink, they'll understand of course).

07.03.2026 01:52 👍 1 🔁 0 💬 0 📌 0

I would argue that it's not odd at all. If you had a Japanese style brand called ōkii mori (大きい森, large forest). The French/English styling would be Okimori or something, not Large Forest. It may even appear in the logo. Just like in the OP. We quite simply do this all the time.

07.03.2026 01:52 👍 1 🔁 0 💬 2 📌 0
screenshot from an online job application form. the question reads "Can you describe specific ways you have integrated AI tools into your development workflow? Please include any custom setups, automations, or use cases beyond single prompt usage" (a red asterisk indicates that this is a required question).

an answer has been typed in the textbox below the question:

"there is a monster in the forest and it speaks with a thousand voices. it will answer any question you pose it, it will offer insight to any idea. it will help you, it will thank you, it will never bid you leave. it will even tell you of the darkest arts, if you know precisely how to ask.

it feels no joy and no sorrow, it knows no right and no wrong. it knows not truth from lie, though it speaks them all the same.
 
it offers its services freely to any passerby, and many will tell you they find great value in its conversation. “you simply must visit the monster—i always just ask the monster.”

there are those who know these forests well; they will tell you that freely offered doesn’t mean it has no price

for when the next traveler passes by, the monster speaks with a thousand and one voices. and when you dream you see the monster; the monster wears your face."

screenshot from an online job application form. the question reads "Can you describe specific ways you have integrated AI tools into your development workflow? Please include any custom setups, automations, or use cases beyond single prompt usage" (a red asterisk indicates that this is a required question). an answer has been typed in the textbox below the question: "there is a monster in the forest and it speaks with a thousand voices. it will answer any question you pose it, it will offer insight to any idea. it will help you, it will thank you, it will never bid you leave. it will even tell you of the darkest arts, if you know precisely how to ask. it feels no joy and no sorrow, it knows no right and no wrong. it knows not truth from lie, though it speaks them all the same. it offers its services freely to any passerby, and many will tell you they find great value in its conversation. “you simply must visit the monster—i always just ask the monster.” there are those who know these forests well; they will tell you that freely offered doesn’t mean it has no price for when the next traveler passes by, the monster speaks with a thousand and one voices. and when you dream you see the monster; the monster wears your face."

applying for jobs again

05.05.2025 14:03 👍 22710 🔁 8760 💬 151 📌 202

This, on the other hand, isn't pedantry. It's not theoretical. It has been shown to be a real issue which affect researcher's careers (along with other artefacts of name ordering). bsky.app/profile/shri...

07.03.2026 01:33 👍 1 🔁 0 💬 0 📌 0

Yes.
Yes!
A thousand times yes!
Can me just accept this and move on?

07.03.2026 01:29 👍 1 🔁 1 💬 1 📌 0

I haven't worked out if it's the right law, my brain is in no shape to.

Of course, heaps as an abstract data type are perfectly serviceable, and the weakened law most certainly suffices. But since you made the point earlier, it got me thinking.

06.03.2026 11:49 👍 0 🔁 0 💬 0 📌 0

Possibly something something Galois connection.

Such as
x•z ≤ y ⇔ x ≤ y-z

At any rate, it seems that `Last`-heaps are exactly usual heaps, so they can't not have an invariant, can they?

06.03.2026 07:17 👍 0 🔁 0 💬 1 📌 0

Thinking of this a bit more. With the `Last` monus, you can build non-heap trees, if I'm not mistaken. Such as Root 57 [Root 0 []]. Which will sort to [57,0] instead of [0,57].

So the weakened monus law don't ensure that every tree is a heap, I think. What's missing?

06.03.2026 07:17 👍 0 🔁 0 💬 1 📌 0
A digital CAPTCHA verification window titled "Select all squares with PIPES" against a plain white background. The window contains a 3×3 grid of numbered squares, mixing literal hardware, smoking pipes, and programming syntax.

A digital CAPTCHA verification window titled "Select all squares with PIPES" against a plain white background. The window contains a 3×3 grid of numbered squares, mixing literal hardware, smoking pipes, and programming syntax.

These captchas just keep getting harder #rstats

05.03.2026 15:58 👍 608 🔁 140 💬 8 📌 2

I discover today that @doisinkidney.com is on here. I swear I searched before posting, but nothing turned out. Sorry.

05.03.2026 21:53 👍 0 🔁 0 💬 1 📌 0

Turns out, translations are linear in projective geometry as well.

04.03.2026 22:24 👍 2 🔁 0 💬 0 📌 0

The translation is very clever. Thanks for sharing!

Nitpick¹: the projective space is 3-dimensional, even if it uses a 4-coordinate system.
Nitpick²: in the Euclidian space, you can still do orthogonal projections.

04.03.2026 12:39 👍 1 🔁 0 💬 0 📌 0


Bonus: in general the projective point will be of the form (kx,ky,kz,k) so the general form of the transformation is (kx,ky,kz,k)↦(kx,ky,kz,kz). Which is still the same division. 4/4

04.03.2026 11:30 👍 0 🔁 0 💬 1 📌 0

However, in the projective space, which is ℝ⁴ quotiented by scaling, dividing by z is (x,y,z,1)↦(x,y,z,z) which can be done by a linear transformation. Hence is much more tractable. 3/4

04.03.2026 11:30 👍 1 🔁 0 💬 1 📌 0

Then a point at (x,y,z) projects to (x/z,y/z,1) which is the point (x/z,y/z) of the target plane.

This is, obviously, a non-linear transform, so it's not obvious how to compute for entire scenes. 2/4

04.03.2026 11:30 👍 0 🔁 0 💬 1 📌 0

I never really thought about how/why projective geometry is useful to model perspective. Turns out, the reason is very simple. Suppose that you have a “camera” at the origin, and you want to project a 3D scene onto the plan at z=1, orthogonal to the z-axis. 1/4

04.03.2026 11:30 👍 4 🔁 0 💬 1 📌 0

Idea: the monus is ℕ×ℕ* where the first n means “I'm branching off of the previous list after n element”, the list then adds pointwise from the n+1st element. This way, within a bucket, you mostly compare single digits. I think it's decently faithful to the algorithmic of radix sort.

04.03.2026 02:46 👍 1 🔁 0 💬 1 📌 0
Monuses and Heaps - Donnacha Oisín Kidney This post is about a simple algebraic structure that I have found useful for algorithms that involve searching or sorting based on some ordered weight. I used it a bit in a pair of papers on graph…

Oisín Kidney has an interesting insight on monus-based heaps doisinkidney.com/posts/2026-0... . It seems to me that this can be used to encode not only order-based sorts but also things like radix sorting. Which is kind of cool if true.

04.03.2026 02:46 👍 4 🔁 1 💬 1 📌 0
Le grave' (symbole gv)' a été édicté par le décret de l'Assemblée du 1er août 1793, et défini comme « le poids d'un décimètre cube
d'eau pure à 4 °C (maxinmum de masse volumique) ». Le grave valait donc environ un kilogramme lorsque utilisé comme mesure de

Le grave' (symbole gv)' a été édicté par le décret de l'Assemblée du 1er août 1793, et défini comme « le poids d'un décimètre cube d'eau pure à 4 °C (maxinmum de masse volumique) ». Le grave valait donc environ un kilogramme lorsque utilisé comme mesure de

Tableau des puissances de 10 de l'unité grave

Tableau des puissances de 10 de l'unité grave

On aurait jamais dû lâcher le grave, l'unité révolutionnaire de 1793 valant un de nos kg actuels

Ça aurait été beaucoup plus cohérent pour parler de la guerre nucléaire à venir

-on dit que Sheffield a été bombardée
-quelle puissance?
-on est sur du mégagrave

03.03.2026 08:58 👍 109 🔁 25 💬 4 📌 1
The light-nanosecond is defined as exactly 29.9792458 cm. It was popularized in information technology as a unit of distance by Grace Hopper as the distance which a photon could travel in one billionth of a second (roughly 30 cm or one foot): "The
speed of light is one foot per
nanosecond"9][10]

The light-nanosecond is defined as exactly 29.9792458 cm. It was popularized in information technology as a unit of distance by Grace Hopper as the distance which a photon could travel in one billionth of a second (roughly 30 cm or one foot): "The speed of light is one foot per nanosecond"9][10]

Astuce élégance et lifestyle:
Arrêtez de parler de triple décimètres ou de trente centimètres comme des ploucs et utilisez à la place la nanoseconde lumière.
De rien.

03.03.2026 15:08 👍 26 🔁 4 💬 5 📌 0

Neither intrinsically, nor, and that's the more interesting question, what the workflow of passkeys is, how I use them, what could go wrong, precautions to prevent things from going wrong. I have, and I mean this quite literally, basically no idea about any of that.

03.03.2026 08:02 👍 0 🔁 0 💬 0 📌 0

I keep hearing about passkeys and how they're so much better than passwords. In fact, I know all about the advantages of passkeys, how it's faster, more secure, etc… But, I'm a pretty nerdy person and yet, nobody has been able to explain to me what passkeys are.

03.03.2026 08:02 👍 0 🔁 0 💬 1 📌 0
The magic of adding random noise to black and white images.
The magic of adding random noise to black and white images. Applications for AMP are open until 11th March! https://jane-st.co/SUM-AMP-2026 The full puzzle is pasted below. Come and see me on tour - live and undithered! https://standupmaths.com/shows Check…

For reference, here's the Stand-up Maths video (from yesterday) www.youtube.com/watch?v=kT4p...

03.03.2026 02:39 👍 0 🔁 0 💬 0 📌 0

Stand-up Maths has a video about dithering, whereby you use patterns of black and white to simulate greyscale (also works with colours). It lets me plug the beautiful French film Renaissance, entirely in black and white with very little dithering! www.imdb.com/title/tt0386...

03.03.2026 02:39 👍 1 🔁 0 💬 1 📌 0

Et Chéri j'ai rétréci les gosses. Ça m'a surpris en le revoyant récemment, mais il était mieux que dans mon souvenir d'enfant. Vraiment un très bon film.

02.03.2026 23:03 👍 0 🔁 0 💬 1 📌 0

Very impressive.

02.03.2026 22:25 👍 0 🔁 0 💬 0 📌 0
Preview
Up and Atom Making hard stuff less hard. Math, physics and computer science.

The channel Up and Atom has quite a lot of maths www.youtube.com/@upandatom/v... . It's not one I've followed closely, but it seems to be quite popular.

01.03.2026 22:05 👍 2 🔁 1 💬 0 📌 0

J'aurais dû ajouter: par exemple en anglais il y a des stratégies différentes pour transcrire le français et l'espagnol aux États Unis et au Royaume Uni. Elles sont largement incomparables.

28.02.2026 02:06 👍 1 🔁 0 💬 0 📌 0

Et même les stratégies établies, ne sont pas toujours les meilleures approximation (meilleures pour quoi au demeurant?).

28.02.2026 02:05 👍 1 🔁 0 💬 1 📌 0

Tout ça c'est compliqué. Transcrire un nom étranger dans sa langue c'est toujours un mélange de stratégies phonétiques établies, stratégies phonétiques ad hoc, et influence de l'orthographe. Les proportion variant. Et il a un aspect culturel: quand on a collectivement choisi un truc on le garde.

28.02.2026 02:03 👍 2 🔁 0 💬 1 📌 0