Viewing profile — gregfjohnson

Been doing this for 20 minutes in the morning for a few decades now. It has had an impact. I am a rather “high gain” person emotionally. I now tend to notice emotions and observe t…

It is a surprising and delightful consequence of this observation that there is a polynomial whose integer-valued roots are exactly the set of all prime numbers.

(Show HN?) There is a deep and lovely connection between the Y-combinator and the classic version of Godel's incompleteness theorem: https://gregfjohnson.com/incompleteness/

One use case that I'm beginning to find useful is to go into a specific directory of code that I have written and am working on, and ask the AI agent (Claude Code in my case) "Plea…

This all reminds me of one of the most foundational and profound papers ever written about software development: Peter Naur's "Programming as Theory Building". I have seen colleagu…

https://gregfjohnson.com

The original comment by Rob Pike and discussion here have implied or used the word "evil". What is a workable definition of "evil"? How about this: Intentionally and knowingly dest…

Build one yourself! Here's an interactive balanced binary tee builder: https://gregfjohnson.com/redblackbuilder.html

(Show HN?) Here is another attempt at providing intuition on complex numbers, the multiplication rule in particular: "Why does complex multiplication have to be the way it is?" htt…

There are bitter and heartstrong arguments on this topic. Brachycephalic breeds with flat faces or short snouts (for example pugs, bulldogs, boxers, Boston terriers) cause anger am…

There is this wonderful concept of "flow state", which I'm sure most of us are familiar with. It was originated by Mihaly Csikszentmihalyi. Many of us in this thread (and Linus's e…

My programming brain has two modes. One is playful mode, and the other is drudge workaday mode. 9-to-5 Monday through Friday is workaday mode. Other times are playful mode. As it t…

I heard an interesting talk recently by a Stanford neuroscientist. He was studying standing waves of brain activity among circularly linked groups of neurons. Neurons can provide b…

I hacked up a version of minesweeper that was “forgiving:” if there was no selection that was provably safe, it gave you a safe move. If you picked any square that was not provably…

On the topic of Microchip and secrecy: I downloaded and installed their IDE, MPLAB X IDE v6.20. It is for a pic3mx chip. The compiler looks like a completely generic gcc, built to …

I wonder if there are any plans to place meat along the bridge to attract mountain lions. Will ecologists try to "train" the wildlife to use the bridge, or just let nature take its…

One possible definition of "random" in this context: Is there any conceivable algorithm, perhaps one that models the entire universe in all of its particulars, that predicts the ne…

PuTTY is a supurb tool. Thank you so much for your efforts over the years.

IBM wrote APL\360 in 360 assembly language. The IBM 5100 personal computer had a small cpu. They wanted APL on the 5100, so they implemented a 360 emulator and ran the original imp…

OK here is my attempt at intuition: Here is an approximation that captures the main effect (the 23.5 degree tilt of the earth's rotation axis) and overlooks secondary effects. Cons…

Thanks, very much appreciate the thoughts and pointers!

This brings to mind something I've wondered about for a while. Sunrise on the shortest day of the year is earlier than sunrise for several days after it. Sunset on these days after…

I've been trying to find discussion of this topic on Hacker News between October 1582 and September 1752, but to no avail. 'cal 9 1752' is .. funny. I guess instead of doing this a…

This short book is (IMHO) one of the best on software design. To me the main point of the book is the importance of well-designed abstractions. The "surface area" of a well-designe…

This same identity can be used to provide geometric intuition as to why i*i must equal -1. This is shown in the diagrams at the bottom of http://gregfjohnson.com/complex/ .