Having the function take a midpoint calculator is fine and there are some advantages to it (e.g. it makes it easy to turn into a linear search if you want to do

Having the function take a midpoint calculator is fine and there are some advantages to it (e.g. it makes it easy to turn into a linear search if you want to do that for some reason). However since writing a midpoint function isn’t always totally straightforward (an incorrectly implemented midpoint will cause correctness issues or even infinite loops), I think it’s nice to have it as a trait. That way there’s little risk of someone using a bad `|x,y| (x + y) / 2` implementation out of laziness. However I 100% agree with you that traits make it really hard to figure out what actual function you’re calling. I wish there was a way to see something like “in your code, this generic function is called with types T1, T2, etc.” and see the trait implementations for those types as well. I’ve actually wanted to contribute this to rust-analyzer for a while.