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fastai: Style

https://docs.fast.ai/dev/style.html
1•tosh•2m ago•0 comments

Get Detach

1•ericfactor•3m ago•0 comments

From Chesterton's fence to Chesterton's gap

https://stephantul.github.io/blog/unfence/
1•stephantul•4m ago•0 comments

A resumable orchestration system for long-running Claude workflows

https://github.com/afsalali1238/Incubator
1•afsalali1238•9m ago•0 comments

Origin – Cursor's GitHub Competitor

https://cursor.com/origin
1•juliangoetze•9m ago•0 comments

Ask HN: How has mobile development changed for you?

2•baddash•10m ago•0 comments

Non-frontal face recognition using GANs and memristor-based classifiers

https://arxiv.org/abs/2606.12074
2•MediaSquirrel•13m ago•0 comments

The Battery Impact of 50 Open GitHub Issues on an M3 Mac

https://gopeek-lovat.vercel.app/blog-github-issues-battery-m3-mac.html
6•formit34•15m ago•1 comments

Custom Memcpy Implementation for ClickHouse

https://github.com/ClickHouse/ClickHouse/blob/master/base/glibc-compatibility/memcpy/memcpy.h
2•prakashqwerty•17m ago•0 comments

Fearless Concurrency on the GPU

https://arxiv.org/abs/2606.15991
1•matt_d•20m ago•0 comments

My Blog Hit the Front Page of Hacker News (and It Was Weird)

https://correresmidestino.com/my-blog-hit-the-front-page-of-hacker-news-and-it-was-weird/
1•frizlab•21m ago•0 comments

R Wins Statistics Award

https://statmodeling.stat.columbia.edu/2026/06/17/53890/
1•Tomte•21m ago•0 comments

Meta CTO Andrew Bosworth Admits the Company's AI Reorg Was 'Atrocious'

https://www.wired.com/story/andrew-bosworth-meta-employees-unrest/
2•reasonableklout•24m ago•0 comments

Dream Appearance Notification

https://drapno.com/
1•dougSF70•25m ago•1 comments

HN rates AI coding agents

https://elolup.com/
3•reStrugly•27m ago•1 comments

Loop Engineering

https://addyo.substack.com/p/loop-engineering
1•kiyanwang•28m ago•0 comments

The Fable 5 Export Controls Harm US Cyber Defense

https://www.lutasecurity.com/post/the-fable-5-export-controls-harm-us-cyber-defense
2•epaga•28m ago•0 comments

Found a useful open-source repo called Undoable

https://github.com/AkhilNam/undoable
1•hellokittydev•31m ago•0 comments

Commodore retro-styled flip phone

https://www.wired.com/story/commodore-callback-8020-is-a-digital-detox-phone-that-isnt-dumb/
1•seomint•31m ago•1 comments

Academic freedom declined in 50 countries

https://academic-freedom-index.net/
1•dash2•31m ago•0 comments

Breakthrough in electron microscopy delivers sharper images of tiniest proteins

https://news.berkeley.edu/2026/06/11/a-breakthrough-in-electron-microscopy-delivers-sharper-image...
2•thunderbong•31m ago•0 comments

Neither Parallel nor Sequential: How DiffusionGemma Commits Tokens

https://arxiv.org/abs/2606.14620
1•Topfi•36m ago•0 comments

Disbatch – turn a PowerShell/batch script into a GUI, with a risk analyzer

https://github.com/SlashRevet/disbatch
1•revet•36m ago•0 comments

Notes Art: iPhone Notes Drawings

https://notes.art/
1•rishikeshs•37m ago•0 comments

Show HN: Fig0 – 0-Manual AI Scientific Figure and Illustration Generator

https://fig0.ai/
1•zizheruan•39m ago•0 comments

Grind LeetCode questions with Claude Code dsa mentor

https://github.com/Stewie-pixel/claude-with-leetcode
1•Stewie-pixel•40m ago•1 comments

Snap Launches $2,195 'Specs' Augmented Reality Glasses

https://www.macrumors.com/2026/06/16/snap-specs-ar-glasses/
2•tosh•42m ago•0 comments

Apple's 2028 iPhones to Use 1.4nm A22 Pro Chips

https://www.macrumors.com/2026/06/16/2028-iphones-a22-pro-chips/
2•tosh•43m ago•0 comments

Yellow spaceship machines used to prevent algae

https://www.bbc.co.uk/news/articles/cpwez5qgj5xo
1•zeristor•44m ago•1 comments

The Coming Quantum National Security Crisis

https://www.foreignaffairs.com/china/coming-quantum-national-security-crisis
3•0in•47m ago•0 comments
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...