fact: Definition addid m n (I : 'cV[R]_m) (J : 'cV[R]_n) := col_mx I J.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path) mathcomp(ssralg fintype perm choice fingroup) mathcomp(matrix bigop zmodp mxalgebra poly) ssrcomplements