End PermSeq.
Notation perm_eql s1 s2 := (perm_eq s1 =1 perm_eq s2).
Notation perm_eqr s1 s2 := (perm_eq^~ s1 =1 perm_eq^~ s2).
Arguments perm_eqP {T s1 s2}.
Arguments perm_eqlP {T s1 s2}.
Arguments perm_eqrP {T s1 s2}.
Prenex Implicits perm_eq.
Hint Resolve perm_eq_refl : core.
Section RotrLemmas.
Variables (n0 : nat) (T : Type) (T' : eqType).
Implicit Type s : seq T.

Lemma rotS n s : n < size s -> rot n.+1 s = rot 1 (rot n s).