proposition: Lemma addOx (F : filter_on T) (f g: T -> V) e x : [O_F e of f] x + [O_F e of g] x = [O_F e of [O_F e of f] + [O_F e of g]] x.
proof: Proof. by move: x; rewrite -/(_ + _ =1 _) {1}addO. Qed.
imports: HB(structures) mathcomp(all_ssreflect ssralg ssrnum) mathcomp(mathcomp_extra boolp classical_sets functions) ereal reals signed topology normedtype prodnormedzmodule