This is an implementation of a 1991 paper on polygon triangulation into Go. So the deepest thinking about how to solve the problem was obviously already done for me, but there were a number of edge cases that I had to invent my own solutions to, and the translation itself involved keeping a lot of context in my head.

I can’t tell you in precise detail what Copilot did, and what I wrote by hand. I wasn’t taking notes or recording my screen. But there’s a reason you don’t see a lot of blocks in there where I forgot to comment anything, because my entire process for this was “type what I want to do in English, and see if Copilot will generate the next snippet, or something close”. I didn’t do this out of bloodyminded dedication to the AI cause, but because it continued to be an extremely effective way to get the code written quickly.

I can give a few specifics:

- My linear algebra is rusty, and Copilot was extremely helpful here. I would often just type the basic thing I was trying to do in pretty vague linear algebra terms, and it would generate the formula.

- I wrote a lot of tests like this https://github.com/osuushi/triangulate/blob/main/internal/sp.... This is a minor thing, but those aren’t copy-pasted. Instead, I would write the first test, and for the most part, I could just type something like `func TestConvertToMonotones_SquareWithHole`, and it would figure out how to adapt the previous test automatically.

- It generates exactly the error strings I want based on context an enormous percentage of the time.

I want to stress that I’m just giving a few examples of things that I specifically remember because I talked about them at the time, not characterizing the majority of the experience of using Copilot. The majority of the experience of using Copilot is that you write comments, and then the things you were about to type appear on the screen before you have to type them.