proposition: Lemma big_enum_in_cond : \big[op/idx]_(i <- enum A | P i) F i = \big[op/idx]_(i in A | P i) F i.
proof: Proof. by rewrite big_filter_cond. Qed.
imports: mathcomp(all_ssreflect ssralg fingroup zmodp poly ssrnum) mathcomp(matrix perm) ssr_ext ssralg_ext fdist