proposition: Lemma remf_id f A : [disjoint domf f & A] -> f.[\ A] = f.
proof: Proof. by move=> /fsetDidPl ->; rewrite restrictfT. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)