proposition: Lemma bigcup_setU_l: forall (U T : Type) (s1 s2 : set U) (f : U -> set T), \bigcup_(i in (s1 :|: s2)) f i <--> \bigcup_(i in s1) f i :|: \bigcup_(i in s2) f i.
proof: Proof. firstorder. Qed.
imports: mathcomp.ssreflect.ssreflect Classes.RelationClasses Classes.Morphisms List Tactics mathcomp(ssrfun ssrbool ssrnat seq)