feat(logic/function/iterate): `f^[n]^[m] = f^[m]^[n]` (#7121)
Prove `f^[n]^[m]=f^[m]^[n]` and improve some docs.
Co-authored-by: Yakov Pechersky <ffxen158@gmail.com>
Co-authored-by: Yury Kudryashov <urkud@urkud.name>
Co-authored-by: Yury G. Kudryashov <urkud@urkud.name>
Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
