extern struct ao_scheme_cons *ao_scheme_read_cons;
extern struct ao_scheme_cons *ao_scheme_read_cons_tail;
extern struct ao_scheme_cons *ao_scheme_read_stack;
extern struct ao_scheme_cons *ao_scheme_read_cons;
extern struct ao_scheme_cons *ao_scheme_read_cons_tail;
extern struct ao_scheme_cons *ao_scheme_read_stack;