Dear all,
My colleague @K_N managed to have half of the lab addicted to Advent of Code 
This year, many problems involve grids, and it proved useful to have a tiny library to handle two-dimensional arrays. So here it is (and via opam):
Nothing sophisticated, and nothing you could not do with Array from the standard library, of course, but useful nonetheless.
Note: This is not a linear algebra library.
Happy hacking,
Jean-Christophe