fact: Definition mpoly_unit : pred {mpoly R[n]} := fun p => (p == (p@_0)%:MP) && (p@_0 \in GRing.unit).
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(order fingroup perm ssralg zmodp poly ssrint) mathcomp(matrix vector) mathcomp(bigenough) ssrcomplements freeg