Ask HN: What's the most creative 'useless' program you've ever written?

Process a UPU PDF with all available airmail destinations into a map that could either show the routing a package will take or the availability for airmail for a given route.

Practically, airmail is just thrown in a sack under a plane by bored airport workers, it often ends up in the wrong country, where a bored airport worker will place it in another sack, and so on until it gets to its destination. There's little elegance to it. Nothing fancy enough to parse a 200 page PDF over.

Most of my stuff is useless. A five-button wireless keyboard, a device that shouts encouragement when you take a tight turn in your car, a back-scratching robot arm, artwork labels for random graffiti tags, an e-ink frame that shows AI generated images of the weather outside the window next to it, https://imgz.org, all of it useless.

I highly recommend js13k (https://js13kgames.com), an annual game jam where your entire game must fit in 13 kilobytes. The tight size limit forces you to get creative with optimization - think procedural generation, custom minimal engines, and code golf techniques that actually matter. While the games might be "useless" in a practical sense, you'll learn more about low-level JavaScript optimization than from most serious projects, all while being part of an incredibly supportive community that loves sharing tricks and tips.

I wrote a Python library for compound interest. It lets you simulate things like irregular deposits/withdrawals, changing interest rates, etc.

I basically use it to plot different scenarios in my future.

I like to write a lot of little programming interpreters and compilers that don't have a whole lot of purpose other than to experiment with a concept. One of these was a little language I called Triad ... an esoteric programming language that used three-letter identifiers because I could quickly treat them like a base-26 int and index an array of 17576 entries, avoiding having to use a hash table implementation.

You can see the C source code for a simple command interpreter that permits three-letter subroutine identifiers here.

https://github.com/jimlawless/triad

I have some other versions that had placeholders for built-in operations that would have made the language Turing-complete but I soon lost interest.

I also implemented a little BASIC interpreter that was only complete enough to write a BASIC program to display the lyrics for the 12 Days of Christmas song:

https://github.com/jimlawless/lazybasic