SCM_ASSERT_TYPE (me, grob_arr, SCM_ARG1, __FUNCTION__, "Grob_array");
SCM_ASSERT_TYPE (scm_is_integer (index), index, SCM_ARG2, __FUNCTION__, "integer");
SCM_ASSERT_TYPE (me, grob_arr, SCM_ARG1, __FUNCTION__, "Grob_array");
SCM_ASSERT_TYPE (scm_is_integer (index), index, SCM_ARG2, __FUNCTION__, "integer");