proposition: Lemma Fid : 'Fix_to(1) = setT.
proof: Proof. by apply/setP=> x /=; rewrite in_setT; apply/afix1P; apply: act1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(choice fintype tuple finfun bigop finset fingroup) mathcomp(action perm primitive_action)