Posts on Chad Crawford

You can save $0.01/gal at the pump with this one trick

Sat, 15 Aug 2026 00:00:00 +0000

I’ve been having a lot of fun vibe-coding with marimo notebooks recently. It also turns out that AI is extremely helpful in collecting data when I’ve got some random questions – stuff that is publicly available but usually too much of a pain in the ass to spend an evening researching.

Surprisingly, AI is quite effective at identifying public data sources and visualizing trends. I did find it still struggles with more complex topics – anything finance especially is a no-go – but it is particularly good at generating plots and doing some basic comparisons.

Ballmer's Guessing Game

Fri, 01 Nov 2024 00:00:00 +0000

John Graham-Cumming did some interesting analysis recently on a problem that Steve Ballmer had used for candidates interviewing at Microsoft. The gist of the problem is as follows:

Nix module trick: Re-evaluating yourself

Sat, 30 Mar 2024 00:00:00 +0000

This is a cool trick for those playing around with Nix’s module system. While developing nix-config-modules, I ran into a semi-unique issue: In the module system I defined a set of hosts and a separate, general set of apps, and hosts could define which apps they could import.

To generate this subset of app configurations, I wanted to be able to re-evaluate all of my app modules with a host argument. In other words, I wanted to be able to write modules like:

A deeper dive on the 4% rule

Mon, 15 Jan 2024 00:00:00 +0000

tl;dr

There’s a common method for calculating how much you need to retire called the 4% rule; but blindly trusting some rule can make it hard to really understand what assumptions were made in generating that rule.

I’ve recently written up an analytical mathematical model that accounts for both interest rates and inflation in the context of calculating retirement annuities. I’m going to talk a bit about how some of these basic rules actually derive their numbers, how it applies to this extension, and what we can learn from using these simple analytical tools.

Redefining Ownership

Fri, 24 Feb 2023 00:00:00 +0000

Software developers are trained to solve problems. We want to write code that makes life as simple and easy as possible, so that our customers can do anything with a simple click of a button. However, when we try to solve too many problems at once, the resulting product solves none of them well. In this article, I’ll discuss how our concept of Ownership underestimates the customer and undermines our products, and what we can do to be better owners.