proposition: Lemma mcoeffE (domf : {fset K}) (E : K -> G) k : [malg k in domf => E k]@_k = if k \in domf then E k else 0.
proof: Proof. exact/fsfun_fun. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap