Definition mark {A: Type} (i: nat) (j: A) := j.

(* Specifications: *)
Lemma swap_mark1 {A} {NA: NatDed A}{SA: SepLog A}:
forall i j (Pi Pj B : A), (i<j)%nat -> B * mark i Pi * mark j Pj = B * mark j Pj * mark i Pi.
Lemma swap_mark0 {A} {NA: NatDed A}{SA: SepLog A}:
forall i j (Pi Pj: A),  (i<j)%nat -> mark i Pi * mark j Pj = mark j Pj * mark i Pi.