John Tromp's Blog

This post is a rewrite of my earlier blog post from Nov 2023 with new insights and updates.

Nesting interpreters A friend of mine enquired about my experience with Lévy-optimal evaluation of lambda calculus, to which I replied: I've tried various others and found them horribly slow on actual benchmarks despite their optimality.

Sensei’s library [1] lists several coordinate systems for the standard 19x19 size Go board.

A rewrite of this blog post with many new insights and updates appeared in Jan 2026 ┬─┬─────────┬─┬─┬ ┬─┬── └─┤ ──┬──── │ │ │ ┼─┼─┬ │ ──┼─┬── │ │ │ │ ├─┘ │ ┬─┼─┼─┬ │ │ │ ├─┘ │ └─┤ │ │ │ │ │ │ │ └─┤ │ │ │ │ │ │ ├─┘ │ │ │ │ └…

Well.

This post discusses how to solve flip puzzles like Simon Tatham’s “Flip” [1] or David Johnson-Davies’s 16 LEDs puzzle [2], where each cell in a rectangular grid represents a light that can be either on or off, and the goal is to have all lights turned on.

Church Numerals Church numerals are the standard way of representing natural numbers in the lambda calculus.

The cryptocurrency space features endless debates about the pros and cons of various possible emission curves.

Many people equate Proof of Work (PoW) with one particular instance of it.

Which scores are finishes?