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...

GitHub CI outages in EU due to status 401 on public repos

https://github.com/orgs/community/discussions/206581
1•baalimago•1m ago•0 comments

A Cop's Case for Flock

https://worksinprogress.co/issue/a-cops-case-for-flock/
1•surprisetalk•1m ago•0 comments

Show HN: AI means the end of software as we know it

https://github.com/jamison/ilc/blob/main/HUMANS.md
1•ilc_genesis_01•2m ago•0 comments

Show HN: I built Pinterest for data visualizations

https://iindex.co/
1•shridharathi•2m ago•0 comments

Novus – A self-improving AI agent that lives on an Android phone

https://github.com/RexHuang/novus
1•RexHuang•3m ago•0 comments

AI agents will not get Estonian ID codes, responsibility will stay with humans

https://news.err.ee/1610132113/ai-agents-will-not-get-estonian-id-codes-and-responsibility-will-s...
1•ilreb•4m ago•0 comments

Branch Computer

https://www.branch.computer/
1•handfuloflight•5m ago•0 comments

High-intensity sprints can trigger molecular changes in the bloodstream

https://www.npr.org/2026/08/23/nx-s1-5939943/high-intensity-hiit-heart-health-exercise
1•mhb•7m ago•0 comments

Wikipedia: The Woozle Effect (Academia)

https://en.wikipedia.org/wiki/Woozle_effect
1•janandonly•7m ago•0 comments

Show HN: Decode, encode, listen, and speak to learn a language

https://www.4tospeak.com/
2•Lublub•8m ago•1 comments

USA Nation got its name on Sep 9, 1776. Americans debated the moniker ever since

https://www.smithsonianmag.com/history/how-did-the-nation-get-its-name-other-suggestions-included...
1•mdp2021•9m ago•1 comments

Squeezing Apple Silicon with Python

https://github.com/eviking/numba-metal/blob/main/docs/research-paper.md
1•eviking•11m ago•0 comments

Show HN: ArrowMetal – Apache Arrow Compute on Apple Silicon GPUs via Metal

https://arrowmetal.org
1•aiexplore369•11m ago•0 comments

Surviving meteors at 99.6%C – what works

https://www.jfreedman.space/post/detecting-a-pebble-at-60-million-kilometers-meteoroid-avoidance-...
1•arnoldspark•11m ago•0 comments

Dbprint

https://github.com/jakubro/dbprint
1•handfuloflight•13m ago•0 comments

Mathematicians discover the worst way to hang a painting

https://www.scientificamerican.com/article/mathematicians-discover-the-worst-way-to-hang-a-painting/
1•sohkamyung•14m ago•0 comments

Forget Sentience: Consciousness as a Service Is All About Realtime Accessibility

https://replyresearch.com/forget-sentience-consciousness-as-a-service-is-all-about-realtime-acces...
1•replyresearch•15m ago•0 comments

Show HN: Arkleon – point-in-time SEC EDGAR fundamentals for Python

https://arkleon.com/
1•Jushuea•17m ago•0 comments

Show HN: A11 – typed streams and reusable actions for agentic apps

https://a11.to
2•helenapankov•18m ago•0 comments

Show HN: CUDA/graphics in QEMU-KVM VMs without passing the Nvidia card to them

https://github.com/reindertpelsma/nvkvm-pv
2•reindertpelsma•19m ago•0 comments

Claudisms – a living banlist of AI-writing tells

https://claudisms.ai/
2•weierstass•19m ago•0 comments

AI and Training PhD Students

https://mathoverflow.net/questions/515026/ai-and-training-phd-students
1•jjgreen•19m ago•0 comments

CUDA Rust: Two Tracks for Writing GPU Kernels

https://developer.nvidia.com/blog/introducing-cuda-rust-two-tracks-for-writing-gpu-kernels/
2•vertigoruntime•19m ago•0 comments

PoC Released for Actively-Exploited MikroTik Unauth SSH Device Takeover

https://github.com/dinosn/mikrotrick-poc
2•ropbear•21m ago•0 comments

Structure over vigilance: Rules for what reviewing the AI misses

https://solutionexplorer.dev/journal/structure-over-vigilance
1•firstordefault•22m ago•0 comments

Show HN: UK pension stress test – two independent engines, cross-checked

https://pensionstresstest.co.uk/
1•Trackermut•22m ago•0 comments

How the Strategic Petroleum Reserve Works

https://www.construction-physics.com/p/how-the-strategic-petroleum-reserve
1•surprisetalk•22m ago•0 comments

PRóspera, the libertarian utopia on a Caribbean island off the coast of Honduras

https://www.abc.net.au/news/2026-08-22/honduras-prospera-libertarian-utopia-caribbean-roatan/1070...
1•pkaeding•23m ago•0 comments

Google warns of lower quality as it revamps Europe search results to avoid fines

https://www.reuters.com/world/google-warns-lower-quality-it-revamps-europe-search-results-avoid-e...
1•thm•23m ago•0 comments

Meet Sally, the Robot Teacher. She Is a Real Doll

https://galratner.substack.com/p/meet-sally-the-robot-teacher-she
2•blartpaul•24m ago•1 comments