Problem using std::prev on ustring iterator

["jeremy.harmon" <jeremy harmon zoho com>]

Hello,

When I try to use std::prev on a ustring const_iterator nothing
happens, operator-- works fine.

Glib::ustring str = "test";
Glib::ustring::iterator iter = str.begin();

std::advance(iter);
printf("%c\n", *iter);

std::prev(iter);
printf("%c\n", *iter);

iter--;
printf("%c\n", *iter);

Output is
e
e
t

Any ideas why it doesn't work?

Thanks
Jeremy