proposition: Lemma eq_span X Y : X =i Y -> (<<X>> = <<Y>>)%VS.
proof: Proof. by move=> eqXY; apply: subv_anti; rewrite !sub_span // => u; rewrite eqXY. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop finfun tuple) mathcomp(ssralg matrix mxalgebra zmodp)