[vmchale]

> how many function types does Rust have again? Three?

It has to, right? ATS has many function types as well, plus stack-allocated closures (I think Rust has that too??)

[steveklabnik]

Rust's closures do not heap allocate unless you box them, like any other struct, because closures are sugar for a struct + a function, that's correct.

(and yes, there are three types of closures, because they need to know if they take said struct by reference, by mutable reference, or by owner.)

[ragnese]

It does have to, because of the way mutation and ownership work. Which is great! But it makes functional programming awkward. The language does not "steward" you toward function composition.