proposition: Lemma erestrictB f g : (f \- g) \_ D = f \_ D \- g \_ D.
proof: Proof. by apply/funext=> x; rewrite /patch/=; case: ifP; rewrite ?sube0. Qed.
imports: HB(structures) mathcomp(all_ssreflect ssralg ssrnum ssrint interval finmap) mathcomp(mathcomp_extra boolp classical_sets fsbigop) mathcomp(functions cardinality set_interval) signed reals ereal topology normedtype sequences