range<I>
operator()(I begin, iterator_difference_t<I> dist, V const & val, R pred_ = R{},
P proj_ = P{}) const
{
RANGES_ASSERT(0 <= dist);
auto &&pred = invokable(pred_);
auto &&proj = invokable(proj_);
while(0 != dist)
{
auto half = dist / 2;
auto middle = next(begin, half);
if(pred(proj(*middle), val))
{
begin = std::move(++middle);
dist -= half + 1;
}
else if(pred(val, proj(*middle)))
{
dist = half;
}
else
return {lower_bound_n(std::move(begin), half, val, std::ref(pred)),
upper_bound_n(next(middle), dist - half - 1, val, std::ref(pred))};
}
return {begin, begin};
}
void insertion_sort_n(I begin, typename std::iterator_traits<I>::difference_type n)
{
auto m = 0;
for(auto it = begin; m != n; ++it, ++m)
{
auto insertion = upper_bound_n(begin, m, *it);
ranges::rotate(insertion, it, std::next(it));
}
}
