Section EqAllPairs.
Variables S T R : eqType.
Implicit Types (f : S -> T -> R) (s : seq S) (t : seq T).

Lemma mem_allpairs f s1 t1 s2 t2 :
s1 =i s2 -> t1 =i t2 ->
[seq f x y | x <- s1, y <- t1] =i [seq f x y | x <- s2, y <- t2].