proposition: Lemma natr_div m d : d %| m -> d%:R \is a @unit R -> (m %/ d)%:R = m%:R / d%:R :> R.
proof: Proof. by rewrite dvdn_eq => /eqP def_m unit_d; rewrite -{2}def_m natrM mulrK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)