proposition: Lemma setU_set_eq_compat {T} (s1 s2 s1' s2' : set T) : s1 <--> s1' -> s2 <--> s2' -> s1 :|: s2 <--> s1' :|: s2'.
proof: Proof. by firstorder. Qed.
imports: mathcomp.ssreflect.ssreflect Classes.RelationClasses Classes.Morphisms List Tactics mathcomp(ssrfun ssrbool ssrnat seq)