static void resize ( nt2::container::table<T,S> &v1
                    , const nt2::container::table<T,S> &v2
                    )
 {
   v1.resize( v2.extent() );
 }
 static bool same_size ( const nt2::container::table<T,S> &v1
                       , const nt2::container::table<T,S> &v2
                       )
 {
   return v1.extent() == v2.extent();
 }