void (*push_head) (void *aux, struct ccase *);
void (*pop_tail) (void *aux, casenumber cnt);
struct ccase *(*get_case) (void *aux, casenumber ofs);
void (*push_head) (void *aux, struct ccase *);
void (*pop_tail) (void *aux, casenumber cnt);
struct ccase *(*get_case) (void *aux, casenumber ofs);