June 14, 2026
Tiny kid, giant brain game
Conversations with a six-year-old on functional programming (2018)
Dad turns math talk into a kid game and the internet instantly wants in
TLDR: A dad turned a hard-to-explain math idea into a guessing game for his six-year-old, and readers loved how simple and playful it was. The comments became a parade of parents sharing their own puzzle games, with the big mood being: learning is way more fun when it feels like play.
A dad reading an extremely brainy paper about abstract math ideas somehow turned it into the most wholesome comment-section flex imaginable: a guessing game for his six-year-old. In the original post, he explains how he described a “function” as a machine: you put something in, something comes out. His son got hooked, especially at the wild idea that a machine could even take other machines as input. From there, the pair invented a game where the child guesses the rule based on examples. Very cute, very nerdy, very “parenting but make it puzzle night.”
But the real show is the community reaction, and readers were absolutely eating this up. One camp declared the whole thing simple and perfect: “Reverse-engineering is fun,” basically summing up the mood in four words. Another wave of parents rushed in with a kind of one-upmanship that was oddly adorable, swapping stories about bath-time math drills, rhyme games, and children happily doing multiplication for entertainment. Yes, the comments somehow turned into a mini-parent Olympics, except everyone was cheering.
The funniest twist? People didn’t just praise the game—they started pitching their own family brain-teasers, from magic-number tricks to secret-rule guessing games involving things like “Roquefort.” There’s no real outrage here, but there is a deliciously nerdy tension: is this genius teaching, reverse-engineering, or just a household quietly turning into a game show? The comments’ verdict: all three, and more please.
Key Points
- •Brent Yorgey wrote that a question from his six-year-old son prompted him to explain functions, types, and free theorems in simple terms.
- •The article describes a function as a machine with inputs and outputs and a type as information about what kinds of things go in and come out.
- •Yorgey defines a free theorem in simplified form as something always true about a function when only its type is known.
- •He notes that the fuller significance of free theorems depends on polymorphism, which he did not attempt to explain to his son.
- •The conversation led Yorgey to create a 'function machine game' where his son guesses a function’s behavior by observing outputs for chosen inputs.