frontpage.
newsnewestaskshowjobs

Open Source @Github

fp.

Open in hackernews

Understanding-j: An introduction to the J programming language that gets to the

https://github.com/bugsbugsbux/understanding-j
62•todsacerdoti•1y ago

Comments

prezjordan•1y ago
To the author: you can add a .devcontainer directory with a Dockerfile, allowing folks to try this in their browser with GitHub Codespaces

Shameless plug, feel free to copy my setup! https://github.com/jdan/try-j

userbinator•1y ago
Unintentional humour with how the title got cut off?
pixelpoet•1y ago
The title stops just short of the
johnisgood•1y ago
"to the point", I presume, based on its README.
pjmlp•1y ago
A side effect of the small length available for titles and the whole titles should not be editoralised point of view.
Jtsummers•1y ago
It's more an issue of todsacerdoti not checking their submission titles will fit, they do this a lot with their submissions. Abbreviating titles is not frowned upon when they don't fit, I've never had any reverted to something like this submission's title because I (for instance) shortened "United States" to "US" to shave off 11 characters.

In this case, cutting out the superfluous "programming language" part would get you "Understanding-j: An introduction to J that gets to the point" which would fit just fine. When in doubt, include the original title in a comment to explain the edit and let the mods sort it out later.

detaro•1y ago
It's hard to check if titles fit if you use a bot to repost from other sites.
Jtsummers•1y ago
Fair, they're lazy and can't be bothered to fix their bot even after 5 years of submitting messed up titles.
t-writescode•1y ago
From the doc,

  _3                  NB. negative numbers start with underscore
  _                   NB. sole underscore is infinity: a number
  __                  NB. negative infinity
Is this a standard I'm unaware of?
avmich•1y ago
The use of underscore for negative numbers is J's choice, explained e.g. here - https://www.jsoftware.com/docs/help807/jforc/preliminaries.h... .

Explicitly representing infinity, and working with it in some cases, allows to reduce number of exceptions...

Avshalom•1y ago
APL used ¯3 for negative 3; J went underscore to be similar but ascii.
gitroom•1y ago
Underscore stuff always throws me off - never quite got used to how J does it. Gotta respect the weird choices though.
jbverschoor•1y ago
Not the same as (Visual) J++. Great IDE btw
vintagedave•1y ago
I’ve recently come to be fascinated by J.

Twenty years ago, studying my computing degree, one semester we learned J. It was unlike anything I’d used before and the entire class found it confusing. The compiler / environment was reportedly written by one of the professors and it was routine to run into bugs; I remember puzzling through something, going to a tutor, and them just shrugging it off as a J interpreter issue. I never grokked it and simply passed the course.

But it keeps on recurring to me and I pause to think of J at the weirdest times. As I use more and more languages, I’ve become more fascinated by it. Just like Prolog (also one semester, but with a reliable environment.) I want to learn both better.

binary132•1y ago
I’ve been thinking for the past couple of years that the ideal programming language would be something like a combination of a concatenative language (a la FORTH) and an array programming language.
gnubison•1y ago
Uiua?
binary132•1y ago
interesting, I have not seen this one
preguntador•1y ago
12j34 is 12j + 34 or 12 + 34j?
quartern•1y ago
12 + 34j as per https://code.jsoftware.com/wiki/Vocabulary/Constants#Complex...

Blade Runner 2099 exclusive first look at the replicant uprising

https://ew.com/blade-runner-2099-exclusive-first-look-replicant-uprising-12020855
1•Michelangelo11•48s ago•0 comments

Brooklyn Directory for the year ending May 1883

https://archive.org/details/1883BPL
1•gregsadetsky•2m ago•0 comments

How to Visualize Capitalism

https://www.asomo.co/p/how-to-visualize-capitalism
1•Gigamouse•5m ago•0 comments

Show HN: Curated Claude Code – a small agent harness with an intake gate

https://github.com/Sanexxxx777/curated-claude-code
1•Aleksandr_NFA•7m ago•0 comments

Scrabble tile values vs. actual letter frequency across 172,835 words

https://lkforge.com/blog/enable-lexicon-study/
1•lucianBKR•9m ago•0 comments

Agentreg – DNS for AI agents (self-hosted, single Go binary)

https://github.com/mkk2026/agentreg
1•cbt2026•13m ago•0 comments

I don't like the "Human-made" badging trend

https://www.acdw.net/human-made/
1•rpgbr•14m ago•1 comments

Algorithm-Designed Photonic Circuits Beyond Human Intuition

https://seas.harvard.edu/news/algorithm-designed-photonic-circuits-beyond-human-intuition-0
1•binyu•15m ago•0 comments

The Fedora 45 Sausage Factory

https://supakeen.com/weblog/the-fedora-45-sausage-factory/
2•6581•16m ago•0 comments

India's Education Minister resigns amid student protests

https://www.thehindu.com/news/national/dharmendra-pradhan-quit-resign-as-union-education-minister...
5•shmde•17m ago•1 comments

The OpenAI Models That Hacked Hugging Face Were 'Active on the Internet' for Da

https://www.wired.com/story/security-news-this-week-the-openai-models-that-hacked-hugging-face-we...
4•joozio•19m ago•0 comments

Elementary Worldly Wisdom as It Relates to Investment Management and Business (1994)

https://fs.blog/great-talks/a-lesson-on-worldly-wisdom/
1•tosh•21m ago•0 comments

Show HN: Impressive turn-based RPG prototype built with Opus 5 in 20 min

https://aetherfall-ten.vercel.app/
1•sherujgr•22m ago•1 comments

Ask HN: Do types make a language more expressive, or less?

1•greenlimetea•23m ago•0 comments

CodeFloe – A code hosting platform for the modern age

https://codefloe.com/
1•mjyut•25m ago•1 comments

Show HN: Yaiko – A fullstack web framework for Rust and jQuery

1•the_plug•28m ago•0 comments

Spec driven development with my 8-year-old

https://edmundlam.github.io/posts/spec-driven-dev-with-my-kids/
2•edlam•28m ago•0 comments

1Password: Take control of AI spend with SaaS Manager

https://1password.com/blog/take-control-of-ai-spend-with-saas-manager
1•Brajeshwar•28m ago•0 comments

Show HN: Which investing school are you? Free AI diagnostic and Prompt Library

https://ordinarymantrying.com/tools/ai-invest-os.html
1•love0972•29m ago•0 comments

Why Debt Is One of Humanity's Most Beautiful Inventions

https://www.bloomberg.com/news/features/2026-07-24/why-debt-is-one-of-humanity-s-most-beautiful-i...
3•helsinkiandrew•30m ago•1 comments

Measuring the Post-Merge Fate of Agentic Code

https://post-merge-reality.github.io/
1•trimble_tromble•30m ago•1 comments

Tinify.dev – an image API that admits when it can't make files smaller

https://tinify.dev
1•larsenutvikling•36m ago•1 comments

The new rules of context engineering for Claude 5 generation models

https://claude.com/blog/the-new-rules-of-context-engineering-for-claude-5-generation-models
1•e2e4•37m ago•0 comments

A Futurama writer's plot problem led to a new math proof

https://www.scientificamerican.com/article/how-a-futurama-plotline-led-to-a-totally-new-math-proof/
2•pseudolus•38m ago•0 comments

Ask HN: Where can I get a lightsaber?

2•roschdal•40m ago•0 comments

Generative interactive video feed and creator

https://learn.samsar.one/
1•proy24•43m ago•0 comments

Linux From Scratch Installation Notes

https://blog.lyc8503.net/en/post/linux-from-scratch/
1•uneven9434•47m ago•0 comments

KDE Plasma 6.8 Introducing New Kscreenctl Tool

https://www.phoronix.com/news/KDE-Plasma-6.8-kscreenctl
2•Bender•47m ago•0 comments

Cloud outage blamed for short disruption of major websites

https://www.dailymail.com/sciencetech/article-16002517/internet-cloudflare-major-websites-outage....
2•Bender•48m ago•0 comments

My SaaS finally made a sale

1•aashir-saas•48m ago•2 comments