proposition: Lemma odivrr a : a != 0 -> a %/? a = Some 1.
proof: Proof. move=> a0; case: odivrP=> [x|H]. by rewrite -{1}[a]mul1r; move/(mulIf a0) <-. by move: (H 1); rewrite mul1r eqxx. 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