proposition: Lemma mcoeff1 k : 1@_k = (k == 1%M)%:R :> R.
proof: Proof. by rewrite mcoeffC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap