proposition: Lemma span_cons v X : (<<v :: X>> = <[v]> + <<X>>)%VS.
proof: Proof. by rewrite !span_def big_cons. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop finfun tuple) mathcomp(ssralg matrix mxalgebra zmodp)