proposition: Lemma big_enum_cond (I : finType) (A : {pred I}) (P : pred I) F : \big[op/x]_(i <- enum A | P i) F i = \big[op/x]_(i in A | P i) F i.
proof: Proof. by rewrite -big_filter_cond; have [e _ _ [/perm_big->]] := big_enumP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div fintype tuple finfun)