proposition: Fact mxrankE m n (A : 'M_(m, n)) : \rank A = (GaussE A).2.
proof: Proof. by rewrite mxrank.unlock unlock /=; case: m n A => [|m] [|n]. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg finalg zmodp matrix)