SCM_ASSERT_TYPE (ga || scm_is_pair (elements), elements, SCM_ARG1, __FUNCTION__, "list or Grob_array");
LY_ASSERT_SMOB (Grob, common, 2);
SCM_ASSERT_TYPE (ga || scm_is_pair (elements), elements, SCM_ARG1, __FUNCTION__, "list or Grob_array");
LY_ASSERT_SMOB (Grob, common, 2);