-struct val_lab *val_labs_first (const struct val_labs *,
- struct val_labs_iterator **);
-struct val_lab *val_labs_first_sorted (const struct val_labs *,
- struct val_labs_iterator **);
-struct val_lab *val_labs_next (const struct val_labs *,
- struct val_labs_iterator **);
-void val_labs_done (struct val_labs_iterator **);
+/* Adding value labels. */
+bool val_labs_add (struct val_labs *, const union value *, const char *);
+void val_labs_replace (struct val_labs *, const union value *, const char *);
+void val_labs_remove (struct val_labs *, struct val_lab *);