If you follow my monthly roundups, (1) who are you?? please say hi (2) you’ll notice a smaller post this time. September was a busy month for me. Lots of feedback on a small post I published “Anecdotally, programmers dislike ‘reduce’”. I finally wrote up a phenomenon I’ve observed for years. It’s a ...

In short: from my experience, people like map and filter, but not reduce. I use functions like map and filter all the time. When I put that code up for review, my peers rarely complain. I get plenty of feedback about other decisions, but not about my use of map and filter. I cannot say the same for ...

Since last month, I released some new stuff at work, clicked a bunch of links, and wrote a little bit. Things I did this August At Ghost, we added analytics for automated email sequences. This helps publishers see how their sequences are doing. This simple feature turned out to be pretty tricky unde...

In short: Vim has a joke autocmd called UserGettingBored that doesn’t do anything. Vim’s automatic commands feature, usually shortened to “autocmd”, lets you run code when various events occur. For example, you could implement an auto-save feature by binding the TextChanged event to the :w command. ...

July! What a month! Things I did this July Gave a talk, for ClimateAction.tech’s “Responsible AI Series”, “What I know about local language models”. “Responsible AI” can feel like a bit of an oxymoron at times, but I hope I shared something useful. Participated in the Zelda Dungeon Marathon. My firs...

In short: I prefer strict tables in SQLite because they avoid some datatype problems, such as putting text in number columns. SQLite has a feature that I think is underrated: strict tables. Strict tables help enforce rigid typing, preventing mistakes like putting text into integer columns. I like th...

Chicago’s weather is pretty lousy most of the year, but when it’s nice, it’s very nice. June blessed the city with dozens of idyllic days. But don’t worry—I still spent most of the time inside on the computer. Things I did I launched my first big project at Ghost: automations! It’s still in beta, bu...

As I write this, we’re about 7 sixteenths through 2026, and it’s about 14 sixteenths through the day. For the sixteenth issue of the Taper online magazine, I split time into sixteenths to think about its passage in a different way. The code, which had to be under 2048 bytes, isn’t terribly complex. ...

My blog turned 16 this month! I did nothing to celebrate, but made some little tools and clicked some links about tech ethics. Things from me this month I published four little tools this month: ZIP Shrinker, a web app that shrinks ZIP files with higher compression ratios A command line tool to do (...

I built ZIP Shrinker, a little browser tool to shrink ZIP files. It also works with formats that are secretly ZIPs underneath, like APK, EPUB, JAR, and many more. Try it out! How does it work? At a high level, this tool (1) re-compresses every file in the ZIP archive with higher compression (2) remo...

In short: I just published Open Link in Unloaded Tab, a little Firefox extension that adds “Open Link in Unloaded Tab” to the right-click context menu. In Firefox, you can unload tabs to save system resources. But there’s no way to open a new tab in the unloaded state…until now! I built a very simpl...

png-cmp is a program I built that checks if two PNGs are visually equivalent. It’s inspired by the cmp command. Here’s how you use it: png-cmp a.png b.png Like cmp, it silently exits if the images are identical, and gives an error if they’re different. Unlike cmp, it checks pixel data, not binary da...

I wrote a simple script that translates text at the command line, completely offline. Here’s an example of how it works on my computer: echo '¿Cómo estás?' | translate # => How are you? It combines a few tools: TranslateGemma, a special-purpose language model for translation Ollama, a tool for runni...

After a busy March, April was a little quieter. But don’t worry, I still have a bunch of little links for you to click on. Things I published GitHub’s uptime hasn’t been great recently. Even though I dislike the Microsoft subsidiary, I wrote “In defense of GitHub’s poor uptime”, which argues that it...

In short: GitHub’s downtime is bad, but uptime numbers can be misleading. It’s not as bad as it looks; more like a D than an F. “Zero nines uptime”? 99.99% uptime, or “four nines”, is a common industry standard. Four nines of uptime is equivalent to 1.008 minutes of downtime per week. GitHub is not ...

March always seems to be my life’s busiest month. Things I wrote and made “The two kinds of error”: in my mind, software errors are divided into two categories: expected and unexpected errors. I finally wrote up this idea I’ve had for a long time. “All tests pass” is a short story about a strange, a...

One night, I wrote a simple tool to pick a random programming language. After shuffling a few times, I landed on Arturo. I decided to try it for fun. What’s Arturo? Best I understand, Arturo is a stack-based programming language. It’s primarily maintained by Yanis Zafirópulos. They published a visio...

I wrote a web app to choose a random programming language. It’s very simple; I hestitate to even call it an “app”! The interesting part was scraping all the languages on Rosetta Code, and even that wasn’t very interesting. But I hope you like it! I learned about a language called Arturo this way, an...

To quote the human.json Protocol: human.json is a protocol for humans to assert authorship of their site content and vouch for the humanity of others. It uses URL ownership as identity, and trust propagates through a crawlable web of vouches between sites. I think this is a neat idea, so I added it ...

Inspired by others, I’m publishing how I use generative AI to write this little blog. General feelings on generative AI Generative AI, like any technology, has tradeoffs. I think the cons far outweigh the pros. In other words, the world would be better off without generative AI. Despite this belief,...

LLM is a popular CLI tool for talking with language models. I built llm-eliza, a plugin to chat with the ELIZA language model. Usage: llm install llm-eliza llm -m eliza "I'm worried about computers." # => What do you think machines have to do with your problem? ELIZA, released in 1966, is a state-of...

In short: in my mind, errors are divided into two categories. Expected errors (think “user entered invalid data”), which are part of normal operation, aren’t the developer’s fault, and should be handled. Unexpected errors (think “null pointer exception”) are the developer’s fault, likely indicate a ...

Things I did and saw this February. Things I made I shipped my first feature at Ghost: Inbox Links. When a member enters their email to log in or sign up, we now show a button that takes them straight to their inbox. In addition to shipping a neat feature, I also enjoyed learning about MX records an...

In short: gzip streams contain metadata, like the operating system that did the compression. I built a tool to read this metadata. I love reading specifications for file formats. They always have little surprises. I had assumed that the gzip format was strictly used for compression. My guess was: a ...

The original Legend of Zelda came out 40 years ago today. With other birthdays on the horizon, like Twilight Princess’s 20th in November, I wanted a calendar that showed the anniversary of every Zelda game. So I made one. Subscribe to this URL in your calendar app: https://evanhahn.com/tape/zelda_an...

Happy new year! Here are some of my notes from the first month of 2026. New job at Ghost! I started a new job as a Staff Engineer at Ghost this month. According to our homepage, Ghost is “for professional publishers to create, share, and grow a business around their content.” I’m looking forward to ...

The Kimi K2.5 large language model was just released. It has 1 trillion parameters. Roughly speaking, the more parameters, the smarter the model. So it’s pretty smart, and is probably considered “state of the art”. But while the world is playing with fancy trillion-parameter chatbots, I was using sm...

I sometimes have to convert between Fahrenheit and Celsius. The actual formula is hard to do in my head, but someone once told me a useful approximation: To convert from Celsius to Fahrenheit, double it and add 30. To convert from Fahrenheit to Celsius, subtract 30 and halve it (the reverse). For ex...