You have arrived at the mid-week hump. Have a $container of $beverage and enjoy some reading before you speed along with the rest of your life.

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Flake Checks in Shell

When a project is built with Nix, it is convenient to also have Nix handle running linters and unit tests etc. I couldn't find information online about how to embed shell scripts as linters in a Nix flake check, but I figured it out and wrote it down for your pleasure.

Full article (3–7 minute read): Flake Checks in Shell

Getting to know you

I have some questions I would like to ask you over the coming weeks. Some of the results may end up in aggregated form as illustrative examples in future articles. Others might inform my writing.

If none of the answers apply cleanly, pick the one that applies best.

Flashcard of the week

I stumbled over a flashcard that pointed me to a text I've wanted to re-read but forgotten where I found. Fortunately, most of my flashcards contain the title of the book they came from, so from the flashcard I was able to locate chapter 7 in the Oxford Handbook of Expertise. Here's the flashcard:

Which are two fast-and-frugal heuristics that can be used to model expert decision making?

The chapter on fast and frugal heuristics is not very well written (among other mistakes, when trying to paint a picture of animal adaptation, it asks the reader to "imagine a shark in the dessert") but it contains much useful knowledge, including the answer to the flashcard:

Counting heuristics and shallow decision trees.

A counting heuristic is a linear model with unit weights. I.e. each of the predictors either adds to or removes from the final score equally much, and then there is some threshold above which the score leads to decision A, otherwise decision B.

A shallow decision tree in this context is more like a linked list: each node leads either to decision A, or to another node. The final node leads either to decision A or decision B.

The main difference between the counting heuristic and the shallow decision tree is that the shallow decision tree focuses on the most predictive question first, and lower-ranked predictors never get a chance to compensate for and counteract the result of the first question if it leads to a decision. This is often better, but not always.

Experts' decision making often appears to use one of these two heuristics, even when the experts themselves are not aware of it. These heuristics have been shown to model expert decisions more accurately than the process the experts themselves think they use.

Longest premium newsletter ever

The previous premium newsletter was so long it had to be split into three emails for deliverability reasons. This is what it contained:

• Part 1:
  • A brief review of 2025 for the blog (2 minute read)
  • Some personal notes on ZFS mirroring (3 minute read)
  • Book recommendation: Vitön by Uusma (1 minute read)
• Part 2:
  • Pathfinding using multi-criteria shortest path (25 minute read)
• Part 3:
  • Forecasts for the ACX 2026 prediction contest (35 minute read)

Subscribers also get access to all past newsletters containing various guides, book recommendations, and links to fun games. (Did you know I have three times now managed to copy the daily Morsle word at 40 WPM? Insane!)

You might not think any of the above is interesting, but you'd still like to support the blog. You can do so for $4 per month, cancelable any time with no questions asked. To upgrade, find the appropriate link below.

Your opinions

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