Oh good point on the hashmapiness of vectors, I forgot about that. That would really change the calculus here.... buuuut

> There is only one coercion from a vector to a list in the code (the first time `rest` is called on the input vector)

So actually.. the whole thing is operating on linked lists.. Is that like a "yikes" moment..? No happy clever vectors? It does seem to still work fine in this case, b/c we pop from one list and append to another and the example is simple.. but generally you want the O() guarantees of vectors or arrays

I'm also a bit surprised reduce is going to give you so much overhead, and destructuring doesn't. It really hardcodes the function to a window size which is a shame.. Last I had to optimize a hot loop in Clojure I found all destructuring terrible for perf (but I think it had to do with type boxing)

> I can count on one hand the number of times I use nth in my project.

Random access is sometimes necessary, but like you say hash-like-vectors cover you here okay. I guess arrays are more about having contiguous memory access. It generally gives you much better cache locality and it will typically make a very sizeable performance difference in a hot loop