proposition: Lemma porbit_cymapcan x : porbit t (cymapcan x) = CM (porbit s x).
proof: Proof. Proof using. rewrite /cymapcan /=. have:= fs_porbitP x => /imsetP[y0 _ ->]. case: pickP => [/= y|]. - by rewrite -eq_porbit_mem => /eqP ->. - by move=> /(_ y0); rewrite porbit_id. 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