+/* Marks an object as being printed, returns 1 if it was already marked */
+int
+ao_scheme_print_mark_addr(void *addr);
+
+int
+ao_scheme_print_mark_poly(ao_poly poly);
+
+/* Notes that printing has started */
+void
+ao_scheme_print_start(void);
+
+/* Notes that printing has ended */
+void
+ao_scheme_print_stop(void);
+