English
If unpaired f is primitive recursive, then unpaired (swap f) is primitive recursive.
Русский
Если unpaired f примитивно-рекурсивна, то unpaired (swap f) тоже примитивно-рекурсивна.
LaTeX
$$$$\\forall f, \\text{Nat.Primrec}(\\text{unpaired } f) \\Rightarrow \\text{Nat.Primrec}(\\text{unpaired}(\\text{Function.swap } f)).$$$$
Lean4
theorem swap' {f} (hf : Nat.Primrec (unpaired f)) : Nat.Primrec (unpaired (swap f)) :=
(hf.comp .swap).of_eq fun n => by simp