check (llx_is_sorted (llx_head (&perm_list), llx_null (&perm_list),
compare_elements_x_y, &aux_data));
llx_destroy (&perm_list, NULL, NULL, &llx_malloc_mgr);
check (llx_is_sorted (llx_head (&perm_list), llx_null (&perm_list),
compare_elements_x_y, &aux_data));
llx_destroy (&perm_list, NULL, NULL, &llx_malloc_mgr);