+ Therefore, an token_number_t must be a valid item_number_t, and we
+ sometimes have to perform the converse transformation. */
+#define token_number_as_item_number(Tok) ((item_number_t) (Tok))
+#define item_number_as_token_number(Ite) ((token_number_t) (Ite))
+
+extern token_number_t start_symbol;