-/* Interator for the architecture's register groups. Pass in NULL,
- returns the first group. Pass in a group, returns the next group,
- or NULL when the last group is reached. */
+/* Iterators for the architecture's register groups. Pass in NULL, returns
+ the first (for next), or last (for prev) group. Pass in a group,
+ returns the next or previous group, or NULL when either the end or the
+ beginning of the group list is reached. */