+/*----- Preliminary utilities ---------------------------------------------*/
+
+/* --- @SOD__CAR@ --- *
+ *
+ * Arguments: @...@ = a nonempty list of arguments
+ *
+ * Returns: The first argument only.
+ */
+
+#if __STDC_VERSION__ >= 199901
+# define SOD__CAR(...) SOD__CARx(__VA_LIST__, _)
+# define SOD__CARx(a, ...) a
+#endif
+