[gtkmm] How do you determine iterator 'type' for get_children.begin() ?

[Jeff Gavin <jeff ezclick net>]

I'm trying to loop through each button in a button box and collect the 
pointers to each of the button widgets.  So far I can do the following 
because I know that there are 8 buttons in the button box.

button[0] = (Gtk::Button *) *(buttonbox->get_children().begin());
button[1] = (Gtk::Button *) *(buttonbox->get_children().begin()++);
button[7] = (Gtk::Button *) *(buttonbox->get_children().end());

The above code compiles and does what I want, it gives me the first, 
second, and last button in my button box.

I cannot figure out what type 'i' should be in this example:

<WHAT TYPE GOES HERE?> i;
for (i = buttonbox->get_children().begin();
     i <= buttonbox->get_children().end();
     i++)
{
  button[j] = *(i);
}

How do you determine the type of the iterator.  I have tried to find an 
example but cannot.  I have read and re-read the online documentation 
for ListHandle and am very lost.

I even compiled the program with the type of 'int' and the compiler 
complained:

cannot convert 
`Glib::Container_Helpers::ListHandleIterator<Glib::Container_Helpers::TypeTraits<Gtk::Widget*> 
>' to `int' in assignment

I was hoping that the error message would give me a hint, but I'm still 
not able to figure out the correct type to use for the iterator.I know 
that an experienced C++ programmer would then know exactly what type to 
use, but alas, I'm still new to C++.

Thanks for your help.

Jeff