Hacker News: xjm

New comment by xjm in "I want to wash my car. The car wash is 50 meters away. Should I walk or drive?"

xjm — Tue, 17 Feb 2026 08:36:02 +0000

Webpage of the text without the intro paragraph

New comment by xjm in "“Erdos problem #728 was solved more or less autonomously by AI”"

xjm — Sun, 11 Jan 2026 20:49:43 +0000

Proving that a particular program terminates does not require deciding the halting problem on arbitrary programs (same for deadlock freedom)

New comment by xjm in "If AI replaces workers, should it also pay taxes?"

xjm — Tue, 16 Dec 2025 10:34:19 +0000

It is not so obvious, some countries have a wealth tax in addition to the income tax.

New comment by xjm in "If AI replaces workers, should it also pay taxes?"

xjm — Tue, 16 Dec 2025 10:28:46 +0000

Only if you pay it off with taxable income.

If you have a lot of assets you can just refinance your loan with more debt.

New comment by xjm in "Addressing the adding situation"

xjm — Tue, 02 Dec 2025 15:27:19 +0000

Part of the Advent of Compiler Optimisations https://xania.org/AoCO2025

Loving it so far!

New comment by xjm in "Search tool that only returns content created before ChatGPT's public release"

xjm — Tue, 02 Dec 2025 12:33:39 +0000

We used a low number _and_ it was a while ago (it would be different if we used the same number spread out on the same time span)

New comment by xjm in "Interactive λ-Reduction"

xjm — Thu, 27 Nov 2025 16:04:32 +0000

I find it much easier to see what is going on when selecting λ-calculus instead of Δ-Nets. E.g. for the mandatory Y Combinator,

λf.(λx.f (x x)) (λx.f (x x))

for which the difference with

λf.(λx.f (x x)) (λx.f (x x) f)

is very clear, whereas with Δ-nets the difference is more subtle. I guess it is because the visualization has more information than with the λ-calculus.

New comment by xjm in "A new bridge links the math of infinity to computer science"

xjm — Wed, 26 Nov 2025 13:04:31 +0000

First sentence:

> All of modern mathematics is built on the foundation of set theory

That's ignoring most of formalized mathematics, which is progressing rapidly and definitely modern. Lean and Rocq for example are founded on type theory, not set theory.

Everybody.codes: same vibe as Advent of Code, but in November

xjm — Wed, 26 Nov 2025 12:43:35 +0000

Article URL: https://everybody.codes

Comments URL: https://news.ycombinator.com/item?id=46056865

Points: 1

# Comments: 0

New comment by xjm in "Await Is Not a Context Switch: Understanding Python's Coroutines vs. Tasks"

xjm — Wed, 26 Nov 2025 12:34:37 +0000

agreed.

tiring.

maybe someone will make an "article-to-prompt" sort of reverse ChatGPT?

But of course someone already did that, and of course it's inside ChatGPT, what was I thinking? Though if I do try it, the prompt I get is not especially pleasant to read: https://chatgpt.com/share/6926f33c-8f98-8011-984e-54e49fdbb0...

New comment by xjm in "Cory Doctorow: "centaurs" and "reverse-centaurs""

xjm — Mon, 15 Sep 2025 16:03:36 +0000

> Thatcher told us, “There is no alternative.” In 1982, Bill Gibson refuted her thus: “The street finds its own uses for things.” > I know which prophet I’m gonna follow.

> Thanks to a free AI model that ran on my modest laptop, in the background while I was doing other work, I was able to write [an accurate quote]

He's right, but it sure sounds like a long fight made of small actions.

New comment by xjm in "Peano's Axioms"

xjm — Mon, 24 Mar 2025 20:24:48 +0000

Another one is Presburger Arithmetic, which is Peano Arithmetic minus the multiplication. What makes it interesting (and useful) is that this removal makes the theory decidable.

https://en.wikipedia.org/wiki/Presburger_arithmetic

New comment by xjm in "The Intelligence Age"

xjm — Wed, 25 Sep 2024 14:16:51 +0000

> fixing the climate

I would be happy to be convinced that climate is an intelligence problem.

One could argue it could be solved with "abundant energy" but if this abundant energy comes from some new intelligence then we are probably several decades away from having it running commercially. I would also be happy to be convinced that we do have this kind of time to act for climate.

New comment by xjm in "Generating sudokus for fun and no profit"

xjm — Fri, 26 Jul 2024 12:43:55 +0000

I counted one trillion or 9! * 3!^8 * 2 : the 8 because you have can choose 3 independent permutations of columns inside column blocks + 1 permutation of column blocks, plus same for rows. Then only one rotation should be counted, because flips are included in col/row permutations.

I think wreath products relate to the second sentence; see this page, which mentions the same result: https://en.wikipedia.org/wiki/Mathematics_of_Sudoku#The_sudo...

New comment by xjm in "France high-speed rail traffic disrupted by 'malicious acts' on Olympic ceremony"

xjm — Fri, 26 Jul 2024 12:21:59 +0000

I'm struggling to try and find information on "exact same modus operandi has been used by far-left movements in the past to disrupt high-speed lines" can you provide some links?

(I'm assuming you are not talking about https://fr.wikipedia.org/wiki/Affaire_de_Tarnac specifically which I would say is not "the exact same".)

New comment by xjm in "France high-speed rail traffic disrupted by 'malicious acts' on Olympic ceremony"

xjm — Fri, 26 Jul 2024 12:11:14 +0000

Though burning random cars might be French, we are talking here about arson with precise strategic targets (although I'm not staying this is more Russia's style)

New comment by xjm in "Arson attacks hit France's train network hours before Olympic ceremony"

xjm — Fri, 26 Jul 2024 12:07:00 +0000

Current discussion: https://news.ycombinator.com/item?id=41076831

New comment by xjm in "France high-speed rail traffic disrupted by 'malicious acts' on Olympic ceremony"

xjm — Fri, 26 Jul 2024 11:35:56 +0000

The scale is different: "thousands of travellers" vs "hundreds of thousands"

One line was blocked because of "two optic fibers" in Germany "for around three hours".

Now in France three main lines are blocked: West, North, East (+ attempt on South), the disruption will probably last for days, it's a lot more than two optic fibers.

New comment by xjm in "Show HN: Every mountain, building and tree shadow mapped for any date and time"

xjm — Sat, 01 Jun 2024 20:48:28 +0000

The Eiffel tower's is fun (:

New comment by xjm in "Coroutines in C (2000)"

xjm — Tue, 27 Feb 2024 23:11:41 +0000

A modular and safe way to achieve this is probably effect handlers. It's like python's yield but can return a value and is scoped like an exception, it's not local to a function call. If you're unfamiliar with it, this article is a good motivation.

Each function, written in direct style, can perform an "effect" when the function wants control to go somewhere else (for c=getchar() and emit(c) here).

Control then goes to the effect handler, in this case probably the caller of the two functions, which decides what to do next: decompressor emits a char? Let's resume the parser's code with the char until it asks for more, then resume decompressor again, etc.

Effects can be efficiently implemented, especially if the continuation is only allowed to be called once (which is the case in OCaml), and allow writing code in direct style, together with type/memory safety. They are also very helpful in a concurrent setting.

An example here : https://effekt-lang.org/docs/casestudies/lexer