It looks similar to what I though I had to write, but I will have to reread it and the documentation to understand it well.

And day 2 seems a bit too complex with my meager J knowledge. OTOH with the J interpreter for android and its terseness it seems the most suited language for programming on a phone, so I will probably stick to it.

[0] https://www.reddit.com/r/adventofcode/comments/e4axxe/2019_d...