proposition: Lemma mcoeff_is_additive k: additive (mcoeff k).
proof: Proof. by move=> g1 g2 /=; rewrite fgaddE fgoppE. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap