fact: Definition ker_mod m0 m1 m2 (M : 'M[R]_(m0,m2)) (N : 'M[R]_(m1,m2)) := rsubmx (ker (col_mx M N)).
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path) mathcomp(ssralg fintype perm choice matrix bigop zmodp mxalgebra poly) ssrcomplements dvdring stronglydiscrete