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

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.

The title stops just short of the

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

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?

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

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

Unintentional humour with how the title got cut off?