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

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

7 comments

·May 3, 2025
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pixelpoet

The title stops just short of the

johnisgood

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

gitroom

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

t-writescode

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

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

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

Unintentional humour with how the title got cut off?