proposition: Lemma prodr_const_nat n m x : \prod_(n <= i < m) x = x ^+ (m - n).
proof: Proof. by rewrite big_const_nat -iteropE. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)