proposition: Lemma big_fset_condE (X : {fset I}) (P : pred I) (F : I -> R) : \big[op/idx]_(i <- X | P i) F i = \big[op/idx]_(i <- [fset i in X | P i]) F i.
proof: Proof. by rewrite big_fset. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)