bool interaction_case_equal (const struct interaction *, const struct ccase *, const struct ccase *);
bool interaction_case_is_missing (const struct interaction *, const struct ccase *, enum mv_class);
int interaction_case_cmp_3way (const struct interaction *, const struct ccase *, const struct ccase *);
bool interaction_case_equal (const struct interaction *, const struct ccase *, const struct ccase *);
bool interaction_case_is_missing (const struct interaction *, const struct ccase *, enum mv_class);
int interaction_case_cmp_3way (const struct interaction *, const struct ccase *, const struct ccase *);