Happy Easter! Or something like that. Happy lunch time! Ah, that has a much more practical appeal.

As an undergrad, I used to forget to eat. I never missed more than a couple meals in a row, but when I became engrossed in my work, it was easy to lose track of time. I've gotten better at taking breaks over the years, but I still lapse from time to time. I had such a lapse yesterday. Today I intend to eat plenty.

When I started working on this derivation on Wednesday, I thought it would take me perhaps a day to finish doing calculus and writing the code. I was wrong by a factor of about three. I spent almost all Friday and Saturday and some time on Thursday and this fine Sunday morning. I thought I finished the calculus by Thursday night, but the results failed sanity checks.

I've written the code now, and it has passed basic tests. Huzzah! Time for a short break.

• Currently drinking: Black coffee