fact: Definition scalar_mx x : 'M[V]_n := \matrix[scalar_mx_key]_(i , j) (x *+ (i == j)).
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg countalg finalg zmodp)