Evaluate J through emacs dynamic modules and libj.so.

I wrote this for fun and because I was getting fed up with how j-mode and org-babel interact.

NB. golfed abelian sandpiles
A =: -[:+/@(-"2((,-)=/~i.2)|.!.0])3&<

viewmat (A^:_) 12000*((>:*[:<.-:)N)=i.,~ N=:101

Setup

If you’re adventurous or curious enough to try this out:

run make setting the appropriate variables j-bin, include, and out.
ensure you have the docs/help addon installed and customize the j-docs-help-index variable to point to where to find the addons/docs/help/index.htm file.
customize the j-profile-ijs variable to point to yours.

Lowlights

J->emacs & emacs->J: marshall data between J and emacs.
calculator: access J prompt in the mini bar through key binding <kbd>M-j</kbd>.
viewmat: if the viewmat.png file changes from executing some J, a buffer pops up to display it inside emacs.
plot: if the plot.pdf file changes from executing some J, the buffer is opened and viewed through pdf-tools.
ob-jpl: facilities for using jpl-mode in org mode.
joogle: emacs procedure that prompts for a J token and opens the corresponding NuVoc page in a browser.
font lock: correctly classifies J tokens by verb, adverb, conjunction, and so on (j-mode misidentifies things like : and a few others) and adds a colors for nouns and names. Basically, with for_a. i. 10 do. font-lock will recognize that a is a binding and color it, bindings such as \'a b\'=. y don’t get highlighted as strings, and things like a: and a. get their own color.
pretty symbols: approximate J in APL glyphs through <kbd>M-p</kbd> and pretty symbol mode.