That's not using the ' for anything like Rust's lifetimes, though; "'a" is just how you refer to some not-further-specified type in ML. A function to reverse a

That's not using the ' for anything like Rust's lifetimes, though; "'a" is just how you refer to some not-further-specified type in ML. A function to reverse a list is polymorphic in what the list contains, for instance, so it would have the type 'a list -> 'a list.