proposition: Lemma axOE s t u : mprv ((s ---> u) ---> (t ---> u) ---> (s :\/: t ---> u)).
proof: Proof. rewrite /Or. do 3 Intro. ApplyH (ax_case s u). Intro. do 2 Apply* 2. Qed.
imports: mathcomp(all_ssreflect) CompDecModal.libs(edone base fset induced_sym) Setoid Morphisms Relation_Definitions