proposition: Lemma unitd1 a : (a \is a GRing.unit) = (a %= 1).
proof: Proof. rewrite -dvdr1; apply/unitrP/dvdrP => [[x [Hxa1 _]]|[x H]]; exists x => //. by split=> //; rewrite mulrC. Qed.
imports: HB(structures) Coq(ssreflect ssrfun ssrbool Arith.Wf_nat) mathcomp(eqtype ssrnat div seq path) mathcomp(ssralg fintype perm tuple choice generic_quotient) mathcomp(matrix bigop zmodp mxalgebra poly) stronglydiscrete