> explicitly written to do this

In that case I want the signature of "this function pre-computes, then returns another function" and "this function takes two arguments" to be different, to show intent.

> achieved through compiler optimisation

Haskell is different in that its evaluation ordering allows this. But in strict evaluation languages, this is much harder, or even forbidden by language semantics.

Here's what Yaron Minsky (an OCaml guy) has to say:

> starting from scratch, I’d avoid partial application as the default way of building multi-argument functions.

https://discuss.ocaml.org/t/reason-general-function-syntax-d...