proposition: Lemma mcoeffU k x k' : << x *g k >>@_k' = x *+ (k == k').
proof: Proof. by rewrite mcoeff_fnd fnd_set fnd_fmap0; case: eqVneq. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap