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/// \file
// Range v3 library
//
// Copyright Eric Niebler 2014-present
// Copyright Casey Carter 2016
//
// Use, modification and distribution is subject to the
// Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// Project home: https://github.com/ericniebler/range-v3
//
#ifndef RANGES_V3_ALGORITHM_EQUAL_RANGE_HPP
#define RANGES_V3_ALGORITHM_EQUAL_RANGE_HPP
#include <range/v3/range_fwd.hpp>
#include <range/v3/algorithm/aux_/equal_range_n.hpp>
#include <range/v3/algorithm/aux_/lower_bound_n.hpp>
#include <range/v3/algorithm/upper_bound.hpp>
#include <range/v3/functional/comparisons.hpp>
#include <range/v3/functional/identity.hpp>
#include <range/v3/functional/invoke.hpp>
#include <range/v3/iterator/operations.hpp>
#include <range/v3/range/access.hpp>
#include <range/v3/range/concepts.hpp>
#include <range/v3/range/traits.hpp>
#include <range/v3/utility/static_const.hpp>
#include <range/v3/view/subrange.hpp>
#include <range/v3/detail/prologue.hpp>
namespace ranges
{
/// \addtogroup group-algorithms
/// @{
RANGES_FUNC_BEGIN(equal_range)
/// \brief function template \c equal_range
template(typename I,
typename S,
typename V,
typename C = less,
typename P = identity)(
requires forward_iterator<I> AND sentinel_for<S, I> AND
indirect_strict_weak_order<C, V const *, projected<I, P>>)
constexpr subrange<I> RANGES_FUNC(equal_range)(
I first, S last, V const & val, C pred = C{}, P proj = P{})
{
if(RANGES_CONSTEXPR_IF(sized_sentinel_for<S, I>))
{
auto const len = distance(first, last);
return aux::equal_range_n(
std::move(first), len, val, std::move(pred), std::move(proj));
}
// Probe exponentially for either end-of-range, an iterator that
// is past the equal range (i.e., denotes an element greater
// than val), or is in the equal range (denotes an element equal
// to val).
auto dist = iter_difference_t<I>{1};
while(true)
{
auto mid = first;
auto d = advance(mid, dist, last);
if(d || mid == last)
{
// at the end of the input range
dist -= d;
return aux::equal_range_n(
std::move(first), dist, val, ranges::ref(pred), ranges::ref(proj));
}
// if val < *mid, mid is after the target range.
auto && v = *mid;
auto && pv = invoke(proj, (decltype(v) &&)v);
if(invoke(pred, val, pv))
{
return aux::equal_range_n(
std::move(first), dist, val, ranges::ref(pred), ranges::ref(proj));
}
else if(!invoke(pred, pv, val))
{
// *mid == val: the lower bound is <= mid, and the upper bound is >
// mid.
return {
aux::lower_bound_n(
std::move(first), dist, val, ranges::ref(pred), ranges::ref(proj)),
upper_bound(std::move(mid),
std::move(last),
val,
ranges::ref(pred),
ranges::ref(proj))};
}
// *mid < val, mid is before the target range.
first = std::move(mid);
++first;
dist *= 2;
}
}
/// \overload
template(typename Rng, typename V, typename C = less, typename P = identity)(
requires forward_range<Rng> AND
indirect_strict_weak_order<C, V const *, projected<iterator_t<Rng>, P>>)
constexpr borrowed_subrange_t<Rng> //
RANGES_FUNC(equal_range)(Rng && rng, V const & val, C pred = C{}, P proj = P{}) //
{
if(RANGES_CONSTEXPR_IF(sized_range<Rng>))
{
auto const len = distance(rng);
return aux::equal_range_n(
begin(rng), len, val, std::move(pred), std::move(proj));
}
return (*this)(begin(rng), end(rng), val, std::move(pred), std::move(proj));
}
RANGES_FUNC_END(equal_range)
namespace cpp20
{
using ranges::equal_range;
}
/// @}
} // namespace ranges
#include <range/v3/detail/epilogue.hpp>
#endif
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