requires
models::Permutable<I>
I bidirectional_buffer(I first, I last, difference_type_t<I> n,
buf_t<I>& buf, Pred& pred, Proj& proj)
{
// Precondition: !pred(proj(*first))
// Precondition: pred(proj(*last))
// Precondition: n == distance(first, last)
STL2_ASSUME(n >= 2);
STL2_ASSUME(n <= buf.size());
// Move the false values into the temporary buffer
// and the true values to the front of the sequence.
auto&& vec = detail::make_temporary_vector(buf);
vec.push_back(__stl2::iter_move(first));
auto middle = __stl2::next(first);
middle = __stl2::partition_move(__stl2::move(middle), last,
__stl2::move(first),
__stl2::back_inserter(vec),
__stl2::ref(pred),
__stl2::ref(proj)).out1();
*middle = __stl2::iter_move(last);
++middle;
__stl2::move(vec, middle);
return middle;
}
requires
models::Permutable<I>
I bidirectional(I first, I last, difference_type_t<I> n,
buf_t<I>& buf, Pred& pred, Proj& proj)
{
// Precondition: !pred(proj(*first))
// Precondition: pred(proj(*last))
// Precondition: n == distance(first, last)
STL2_ASSUME(n >= difference_type_t<I>(1));
if (n == difference_type_t<I>(1)) {
__stl2::iter_swap(first, last);
return last;
}
// n >= 2
if (n <= buf.size()) {
return stable_part::bidirectional_buffer(
__stl2::move(first), __stl2::move(last),
n, buf, pred, proj);
}
const auto half_n = n / 2;
auto middle = __stl2::next(first, half_n);
auto pp1 = stable_part::bidirectional_reduce_back(
__stl2::move(first), middle, half_n, buf, pred, proj);
auto pp2 = stable_part::bidirectional_reduce_front(
middle, __stl2::move(last), n - half_n, buf, pred, proj);
return __stl2::rotate(__stl2::move(pp1), __stl2::move(middle),
__stl2::move(pp2)).begin();
}
requires
models::Permutable<I>
ext::range<I>
forward(I first, difference_type_t<I> n,
buf_t<I>& buf, Pred& pred, Proj& proj)
{
// Precondition: !pred(proj(*first)))
STL2_ASSUME(n > 0);
auto middle = __stl2::next(first);
if (n == difference_type_t<I>(1)) {
return {__stl2::move(first), __stl2::move(middle)};
}
// n >= 2
if (n <= buf.size()) {
return stable_part::forward_buffer(
__stl2::move(first), __stl2::move(middle),
n, buf, pred, proj);
}
const auto half_n = n / 2;
auto res1 = stable_part::forward(__stl2::move(first), half_n, buf, pred, proj);
auto res2 = stable_part::forward_reduce(res1.end(), n - half_n, buf, pred, proj);
auto pp = __stl2::rotate(__stl2::move(res1.begin()),
__stl2::move(res1.end()),
__stl2::move(res2.begin())).begin();
return {__stl2::move(pp), __stl2::move(res2.end())};
}
requires RandomAccessIterator<I>()
{
STL2_ASSUME(n <= count_);
current() += n;
count_ -= n;
return *this;
}
tagged_pair<tag::in(I), tag::out(O)>
copy_n(I first_, DifferenceType<I> n, O result) {
STL2_ASSUME(n >= 0);
auto norig = n;
auto first = __stl2::ext::uncounted(first_);
for(; n > 0; ++first, ++result, --n) {
*result = *first;
}
return {__stl2::ext::recounted(first_, first, norig), result};
}
void skip_false(I& last, difference_type_t<I>& n, Pred& pred, Proj& proj)
{
// Move last backward past values that do not satisfy pred.
// Precondition: pred(proj(*(last - n)))
STL2_ASSUME(n > 0);
// Ensures: n == 0 || pred(proj(*last))
do {
--last;
} while (--n != 0 && !pred(proj(*last)));
}
requires
models::Permutable<I>
ext::range<I>
forward_buffer(I first, I next, difference_type_t<I> n,
buf_t<I>& buf, Pred& pred, Proj& proj)
{
// Precondition: !pred(proj(*first)))
// Precondition: __stl2::next(first) == next
STL2_ASSUME(n >= 2);
STL2_ASSUME(n <= buf.size());
auto&& vec = detail::make_temporary_vector(buf);
vec.push_back(__stl2::iter_move(first));
auto counted = __stl2::make_counted_iterator(
ext::uncounted(next), n - 1);
auto pp = __stl2::partition_move(
__stl2::move(counted), default_sentinel{},
__stl2::move(first), __stl2::back_inserter(vec),
__stl2::ref(pred), __stl2::ref(proj)).out1();
auto last = __stl2::move(vec, pp).out();
return {__stl2::move(pp), __stl2::move(last)};
}
requires
models::Sortable<I, Comp, Proj>
I choose_pivot(I first, I last, Comp& comp, Proj& proj)
{
STL2_ASSUME(first != last);
I mid = first + difference_type_t<I>(last - first) / 2;
--last;
// Find the median:
return [&](auto&& a, auto&& b, auto&& c) {
return comp(a, b)
? (comp(b, c) ? mid : (comp(a, c) ? last : first))
: (comp(a, c) ? first : (comp(b, c) ? last : mid ));
}(proj(*first), proj(*mid), proj(*last));
}
inline I merge_n_with_buffer(I f0, DifferenceType<I> n0,
I f1, DifferenceType<I> n1,
buf_t<I>& buf, Comp& comp, Proj& proj) {
STL2_ASSUME(n0 <= buf.size());
auto&& vec = make_temporary_vector(buf);
__stl2::move(__stl2::make_counted_iterator(f0, n0),
__stl2::default_sentinel{},
__stl2::back_inserter(vec));
return __stl2::merge_move(
vec.begin(), vec.end(),
__stl2::make_counted_iterator(__stl2::move(f1), n1),
__stl2::default_sentinel{},
__stl2::move(f0), __stl2::ref(comp),
__stl2::ref(proj), __stl2::ref(proj)).out();
}
requires
models::Permutable<I>
I bidirectional_reduce_back(I first, I last, difference_type_t<I> n,
buf_t<I>& buf, Pred& pred, Proj& proj)
{
// Precondition: !pred(proj(*first))
// Precondition: n == __stl2::distance(first, last)
STL2_ASSUME(n >= difference_type_t<I>(1));
stable_part::skip_false(last, n, pred, proj);
if (n == difference_type_t<I>(0)) {
return first;
}
return stable_part::bidirectional(first, last, n, buf, pred, proj);
}
requires
models::Permutable<I>
I bidirectional_reduce_front(I first, I last, difference_type_t<I> n,
buf_t<I>& buf, Pred& pred, Proj& proj)
{
// Precondition: pred(proj(*last))
// Precondition: n == distance(first, last)
STL2_ASSUME(n >= difference_type_t<I>(0));
stable_part::skip_true(first, n, pred, proj);
if (n == difference_type_t<I>(0)) {
return __stl2::move(++last);
}
return stable_part::bidirectional(first, last, n, buf, pred, proj);
}
requires
models::IndirectlyCopyable<I, O>
tagged_pair<tag::in(I), tag::out(O)>
copy_n(I first_, difference_type_t<I> n, O result)
{
STL2_ASSUME(n >= 0);
auto norig = n;
auto first = __stl2::ext::uncounted(first_);
for(; n > 0; ++first, ++result, --n) {
*result = *first;
}
return {
__stl2::ext::recounted(first_, first, norig),
__stl2::move(result)
};
}
I is_heap_until_n(I first, const DifferenceType<I> n,
Comp comp_ = Comp{}, Proj proj_ = Proj{}) {
STL2_ASSUME(0 <= n);
auto&& comp = __stl2::as_function(comp_);
auto&& proj = __stl2::as_function(proj_);
DifferenceType<I> p = 0, c = 1;
I pp = first;
while (c < n) {
I cp = first + c;
if (comp(proj(*pp), proj(*cp))) {
return cp;
}
++c;
++cp;
if (c == n || comp(proj(*pp), proj(*cp))) {
return cp;
}
++p;
++pp;
c = 2 * p + 1;
}
return first + n;
}
STL2_CONSTEXPR_EXT counted_iterator operator+(difference_type_t<I> n) const
requires RandomAccessIterator<I>()
{
STL2_ASSUME(n <= count_);
return {current() + n, count_ - n};
}
constexpr T* operator->() const noexcept {
STL2_ASSUME(ptr_);
return ptr_;
}
requires RandomAccessIterator<I>()
{
STL2_ASSUME(n < count_);
return current()[n];
}
constexpr T& operator*() const noexcept {
STL2_ASSUME(ptr_);
return *ptr_;
}