void set_on_completed_callback(
boost::shared_ptr<when_each<Sequence, F> > when)
{
set_when_each_on_completed_callback_impl<Sequence, F>
set_on_completed_callback_helper(when);
set_on_completed_callback_helper.apply(when->lazy_values_);
}
void set_on_completed_callback(wait_n<Sequence>& wait,
Callback const& callback)
{
set_wait_on_completed_callback_impl<Sequence, Callback>
set_on_completed_callback_helper(wait, callback);
set_on_completed_callback_helper.apply(wait.lazy_values_);
}