English
Interchanging the roles of M and N in a perfect pairing yields a perfect pairing in the opposite direction.
Русский
Замена ролей M и N в совершенной парировке образует совершенную парировку в обратном направлении.
LaTeX
$$$$ p.flip.{\\rm IsPerfPair} $$$$
Lean4
/-- Turn a perfect pairing between `M` and `N` into an isomorphism between `M` and the dual of `N`.
-/
noncomputable def toPerfPair : M ≃ₗ[R] Dual R N :=
.ofBijective { toFun := _, map_add' x y := by simp, map_smul' r x := by simp } <| IsPerfPair.bijective_left p