proposition: Lemma directvE (S : addv_expr) : directv (unwrap S) = (\dim (unwrap S) == unwrap (addv_dim S)).
proof: Proof. by []. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop finfun tuple) mathcomp(ssralg matrix mxalgebra zmodp)