proposition: Lemma big_cond_mulrn r: (\sum_(i <- r | P i) F i = \sum_(i <- r) F i *+ P i)%R.
proof: Proof. by rewrite big_mkcond; apply: eq_bigr => i; rewrite mulrb. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset order) mathcomp(ssralg)