Footprints in the sand from Thomas Greco

Trials and tribulations of a programmer with a deep appreciation for deterministic software... and also, life!
Some posts first appear at Hindley Milner Systems and are mirrored here. Enjoy!

$Hand-inked isometric drawing of an 80 mm refractor telescope on a tripod, with a flat blue cast shadow$

Fig. 21 — Telescope, 80 mm f/10 on an EQ2 mount

28 Oct 2026λ hindleymilner.com6 min
Prevent Impossible States Pt. 2 - State Transitions
Model a timer's states and events with TypeScript unions, then define the rules for moving between them.
typescript state-machines union-types series
27 Oct 2026tgrecojs.com1 min
Life of a stargazer
featuring Colorfigures
stargazing hobbies personal
27 Oct 2026λ hindleymilner.com4 min
Prevent Impossible States Pt. 1 - Union Types
Use TypeScript discriminated unions to require the right fields, narrow object types, and catch unhandled cases.
typescript union-types category-theory series
1 May 2018tgrecojs.com5 min
Fun with Functors
JavaScript arrays are functors. What that means, the two laws they follow, and how to build a Box of your own.
javascript functional-programming functors

Prevent Impossible States Pt. 2 - State Transitions

Life of a stargazer

Prevent Impossible States Pt. 1 - Union Types

Fun with Functors