Arguments fpathP {T f x p}.
Arguments loopingP {T f x n}.
Arguments trajectP {T f x n y}.
Prenex Implicits traject.
Section UniqCycle.
Variables (n0 : nat) (T : eqType) (e : rel T) (p : seq T).
Hypothesis Up : uniq p.

Lemma prev_next : cancel (next p) (prev p).