proposition: Lemma intrB m n : (m - n)%:~R = m%:~R - n%:~R :> R.
proof: Proof. by rewrite intrD intrN. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)