proposition: Lemma natr_prod I r P (F : I -> nat) : (\prod_(i <- r | P i) F i)%:R = \prod_(i <- r | P i) (F i)%:R :> R.
proof: Proof. exact: (big_morph _ natrM). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)