bool mv_add_num (struct missing_values *, double);
void mv_pop_value (struct missing_values *, union value *);
bool mv_replace_value (struct missing_values *, const union value *, int idx);
bool mv_add_num (struct missing_values *, double);
void mv_pop_value (struct missing_values *, union value *);
bool mv_replace_value (struct missing_values *, const union value *, int idx);