I did not write the type class declarations in this file but they are generic representation for type classes I did write.

I picked an extreme example. Sadly I don't have a great example of more "business" style code in a public repo to show you right now, but I have had a lot of success using LLMs to write CRUDy haskell APIs and such as well.

I think LLM output quality is wildly dependent on how we prompt them. And I don't just mean giving a really specific design for it to implement or whatever. I have no real proof but suspect that every little thing about how we communicate to an LLM will impact the quality of the output. Like even just our choice of language in how we describe a problem.

I have a friend who is not remotely a programmer who tried to vibe code a big python project with Claude. He came up with really detailed designs and worked through them over and over with Claude. He hit some major roadblocks and asked me to look over the code. I was really shocked at the quality of the code out.

There was tons and tons of dead code, unnecessary repeated expensive computations, no real sense of an architecture, etc. I didn't even re-write it by hand, I just asked claude things like "decompose all the functions to a reasonable size", "use modules to organize the code", "remove dead code", "write pure functions", "parse dont validate", etc. It eliminated thousands of lines of crap, became way easier to read, and improved the speed of the program by orders of magnitude.