Comment by eru

> [...] and I think it's underrated that the kinds of functions where TCO is applicable tend to be so simple that they are not really that inelegant when expressed imperatively.

I suspect you are only thinking of patterns that are basically equivalent to a loop. I might agree with that.

TCO really shines when you want to implement state machines. See eg https://news.ycombinator.com/item?id=43076088 for an example where using tail calls in Python's interpreter loop gives nice performance benefits. Similar also for LUA.

> [...] I'd concede that experienced FP programmers might be unlikely to accidentally break others' TCO.

Compiler (or linter) checkable annotations would help here. You are right that you want to make it possible for programmers to statically assert somehow that their function call is a tail call.

Btw this reminds me: recursion isn't just something you do in computation, but also in data structures (amongst other things). In eg Rust the members of your data structure are typically just laid out one after another, but when you have a recursive structure (and in certain other cases) you need to box it, otherwise you'd get an infinitely large data structure. Boxing is more or less equivalent to using indirection via a pointer.

However, unboxing isn't really like TCO. It's more like in-lining.