v3/algorithm/equal_range.hpp

0001 /// \file
0002 // Range v3 library
0003 //
0004 //  Copyright Eric Niebler 2014-present
0005 //  Copyright Casey Carter 2016
0006 //
0007 //  Use, modification and distribution is subject to the
0008 //  Boost Software License, Version 1.0. (See accompanying
0009 //  file LICENSE_1_0.txt or copy at
0010 //  http://www.boost.org/LICENSE_1_0.txt)
0011 //
0012 // Project home: https://github.com/ericniebler/range-v3
0013 //
0014 #ifndef RANGES_V3_ALGORITHM_EQUAL_RANGE_HPP
0015 #define RANGES_V3_ALGORITHM_EQUAL_RANGE_HPP
0016
0017 #include <range/v3/range_fwd.hpp>
0018
0019 #include <range/v3/algorithm/aux_/equal_range_n.hpp>
0020 #include <range/v3/algorithm/aux_/lower_bound_n.hpp>
0021 #include <range/v3/algorithm/upper_bound.hpp>
0022 #include <range/v3/functional/comparisons.hpp>
0023 #include <range/v3/functional/identity.hpp>
0024 #include <range/v3/functional/invoke.hpp>
0025 #include <range/v3/iterator/operations.hpp>
0026 #include <range/v3/range/access.hpp>
0027 #include <range/v3/range/concepts.hpp>
0028 #include <range/v3/range/traits.hpp>
0029 #include <range/v3/utility/static_const.hpp>
0030 #include <range/v3/view/subrange.hpp>
0031
0032 #include <range/v3/detail/prologue.hpp>
0033
0034 namespace ranges
0035 {
0036     /// \addtogroup group-algorithms
0037     /// @{
0038     RANGES_FUNC_BEGIN(equal_range)
0039
0040         /// \brief function template \c equal_range
0041         template(typename I,
0042                  typename S,
0043                  typename V,
0044                  typename C = less,
0045                  typename P = identity)(
0046             requires forward_iterator<I> AND sentinel_for<S, I> AND
0047                 indirect_strict_weak_order<C, V const *, projected<I, P>>)
0048         constexpr subrange<I> RANGES_FUNC(equal_range)(
0049             I first, S last, V const & val, C pred = C{}, P proj = P{})
0050         {
0051             if(RANGES_CONSTEXPR_IF(sized_sentinel_for<S, I>))
0052             {
0053                 auto const len = distance(first, last);
0054                 return aux::equal_range_n(
0055                     std::move(first), len, val, std::move(pred), std::move(proj));
0056             }
0057
0058             // Probe exponentially for either end-of-range, an iterator that
0059             // is past the equal range (i.e., denotes an element greater
0060             // than val), or is in the equal range (denotes an element equal
0061             // to val).
0062             auto dist = iter_difference_t<I>{1};
0063             while(true)
0064             {
0065                 auto mid = first;
0066                 auto d = advance(mid, dist, last);
0067                 if(d || mid == last)
0068                 {
0069                     // at the end of the input range
0070                     dist -= d;
0071                     return aux::equal_range_n(
0072                         std::move(first), dist, val, ranges::ref(pred), ranges::ref(proj));
0073                 }
0074                 // if val < *mid, mid is after the target range.
0075                 auto && v = *mid;
0076                 auto && pv = invoke(proj, (decltype(v) &&)v);
0077                 if(invoke(pred, val, pv))
0078                 {
0079                     return aux::equal_range_n(
0080                         std::move(first), dist, val, ranges::ref(pred), ranges::ref(proj));
0081                 }
0082                 else if(!invoke(pred, pv, val))
0083                 {
0084                     // *mid == val: the lower bound is <= mid, and the upper bound is >
0085                     // mid.
0086                     return {
0087                         aux::lower_bound_n(
0088                             std::move(first), dist, val, ranges::ref(pred), ranges::ref(proj)),
0089                         upper_bound(std::move(mid),
0090                                     std::move(last),
0091                                     val,
0092                                     ranges::ref(pred),
0093                                     ranges::ref(proj))};
0094                 }
0095                 // *mid < val, mid is before the target range.
0096                 first = std::move(mid);
0097                 ++first;
0098                 dist *= 2;
0099             }
0100         }
0101
0102         /// \overload
0103         template(typename Rng, typename V, typename C = less, typename P = identity)(
0104             requires forward_range<Rng> AND
0105                 indirect_strict_weak_order<C, V const *, projected<iterator_t<Rng>, P>>)
0106         constexpr borrowed_subrange_t<Rng> //
0107         RANGES_FUNC(equal_range)(Rng && rng, V const & val, C pred = C{}, P proj = P{}) //
0108         {
0109             if(RANGES_CONSTEXPR_IF(sized_range<Rng>))
0110             {
0111                 auto const len = distance(rng);
0112                 return aux::equal_range_n(
0113                     begin(rng), len, val, std::move(pred), std::move(proj));
0114             }
0115
0116             return (*this)(begin(rng), end(rng), val, std::move(pred), std::move(proj));
0117         }
0118
0119     RANGES_FUNC_END(equal_range)
0120
0121     namespace cpp20
0122     {
0123         using ranges::equal_range;
0124     }
0125     /// @}
0126 } // namespace ranges
0127
0128 #include <range/v3/detail/epilogue.hpp>
0129
0130 #endif