proposition: Lemma leif_0_sum (I : finType) (P C : pred I) (E : I -> R) : (forall i, P i -> 0 <= E i ?= iff C i) -> 0 <= \sum_(i | P i) E i ?= iff [forall (i | P i), C i].
proof: Proof. by move/leif_sum; rewrite big1_eq. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)