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

48 todsacerdoti 10 5/3/2025, 8:40:59 PM github.com ↗

Comments (10)

pixelpoet · 9h ago

The title stops just short of the

johnisgood · 4h ago

"to the point", I presume, based on its README.

pjmlp · 3h ago

A side effect of the small length available for titles and the whole titles should not be editoralised point of view.

t-writescode · 7h 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?

Avshalom · 15m ago

APL used ¯3 for negative 3; J went underscore to be similar but ascii.

avmich · 6h 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...

prezjordan · 10h 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

jbverschoor · 2h ago

Not the same as (Visual) J++. Great IDE btw

gitroom · 5h ago

Underscore stuff always throws me off - never quite got used to how J does it. Gotta respect the weird choices though.

userbinator · 9h ago

Unintentional humour with how the title got cut off?