proposition: Lemma count_mem_iota a b i : count_mem i (iota a b) = (a <= i < a + b).
proof: Proof. by rewrite count_uniq_mem ?iota_uniq // mem_iota. Qed.
imports: mathcomp.ssreflect.ssreflect mathcomp(ssrbool ssrfun ssrnat eqtype fintype choice seq) mathcomp(finset bigop path binomial)