proposition: Lemma canporbitP x : x \in porbit s (canporbit x).
proof: Proof. Proof using. rewrite /canporbit /= porbit_sym. case: pickP => [x0 //|]. by move => /(_ x) /= _. Qed.
imports: mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq choice fintype) mathcomp(tuple finfun finset path bigop) mathcomp(fingroup perm action) mathcomp(ssralg matrix mxalgebra algC classfun) partition tools sorted permcomp fibered_set cycles