146     auto dlp = discrete_legendre<Real>(n, 0);  in interior_velocity_filter()  local
148     coeffs[1] = 1/dlp.norm_sq(1);  in interior_velocity_filter()
151         dlp.next_prime();  in interior_velocity_filter()
152         coeffs[l] = dlp.next_prime()/ dlp.norm_sq(l);  in interior_velocity_filter()
164         dlp = discrete_legendre<Real>(n, arg);  in interior_velocity_filter()
168             dlp.next();  in interior_velocity_filter()
169             f[j] += coeffs[l]*dlp.next();  in interior_velocity_filter()
181     auto dlp = discrete_legendre<Real>(n, sn);  in boundary_velocity_filter()  local
183     coeffs[1] = 1/dlp.norm_sq(1);  in boundary_velocity_filter()
191         coeffs[l] = dlp.next_prime()/ dlp.norm_sq(l);  in boundary_velocity_filter()
199         dlp = discrete_legendre<Real>(n, arg);  in boundary_velocity_filter()
203             f[k] += coeffs[l]*dlp.next();  in boundary_velocity_filter()
218     auto dlp = discrete_legendre<Real>(n, sn);  in acceleration_filter()  local
223         coeffs[l] = dlp.next_dbl_prime()/ dlp.norm_sq(l);  in acceleration_filter()
231         dlp = discrete_legendre<Real>(n, arg);  in acceleration_filter()
234             f[k] += coeffs[l]*dlp.next();  in acceleration_filter()