Re: Problem using std::prev on ustring iterator

[Jonathan Wakely <gtkmm kayari org>]

On 18 March 2016 at 18:11, Jonathan Wakely <gtkmm kayari org> wrote:
> On 18 March 2016 at 17:57, jeremy.harmon wrote:
> > 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?
>
> Because unlike std::advance, std::prev doesn't modify its argument, it
> returns the new iterator instead.
>
> http://en.cppreference.com/w/cpp/iterator/prev

So, for completeness, you probably want to do this instead:

iter = std::prev(iter);

or std::advance(iter, -1)