operator-() [2/2]

Matrix * Matrix::operator-

(

const Matrix &

m

)

const

Definition at line 428 of file matrix.cpp.

{
  auto R = get_ring();
  if (R != m.get_ring())
    {
      ERROR("matrices have different base rings");
      return nullptr;
    }
  if (rows()->rank() != m.rows()->rank() || cols()->rank() != m.cols()->rank())
    {
      ERROR("matrices have different shapes");
      return nullptr;
    }
 
  const FreeModule *F = rows();
  const FreeModule *G = cols();
  const_monomial deg;
 
  if (!rows()->is_equal(m.rows())) F = R->make_FreeModule(n_rows());
 
  if (!cols()->is_equal(m.cols())) G = R->make_FreeModule(n_cols());
 
  auto D = R->degree_monoid();
  if (EQ == D->compare(degree_shift(), m.degree_shift()))
    deg = degree_shift();
  else
    deg = D->make_one();
 
  MatrixConstructor mat(F, G, deg);
  for (int i = 0; i < n_cols(); i++)
    mat.set_column(i, R->subtract_vec(elem(i), m[i]));
  return mat.to_matrix();
}

References cols(), degree_shift(), elem(), EQ, ERROR, FreeModule, G, get_ring(), is_equal(), Matrix(), MatrixConstructor, n_cols(), n_rows(), operator-(), FreeModule::rank(), rows(), MatrixConstructor::set_column(), and MatrixConstructor::to_matrix().