-struct categoricals *categoricals_create (const struct variable **v, size_t n_vars,
- const struct variable *wv, enum mv_class exclude);
+typedef void update_func (void *user_data,
+ const struct variable *wv,
+ const struct variable *catvar,
+ const struct ccase *c, void *aux);
+
+typedef void *user_data_create_func (void);
+
+struct categoricals *categoricals_create (const struct variable *const *v, size_t n_vars,
+ const struct variable *wv, enum mv_class exclude,
+ user_data_create_func *udf,
+ update_func *update, void *update_aux);