libcxx/include/__algorithm/lower_bound.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef _LIBCPP___ALGORITHM_LOWER_BOUND_H
  10 #define _LIBCPP___ALGORITHM_LOWER_BOUND_H
  11
  12 #include <__algorithm/comp.h>
  13 #include <__algorithm/half_positive.h>
  14 #include <__algorithm/iterator_operations.h>
  15 #include <__config>
  16 #include <__functional/identity.h>
  17 #include <__functional/invoke.h>
  18 #include <__iterator/advance.h>
  19 #include <__iterator/distance.h>
  20 #include <__iterator/iterator_traits.h>
  21 #include <__type_traits/is_callable.h>
  22 #include <__type_traits/remove_reference.h>
  23
  24 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  25 #  pragma GCC system_header
  26 #endif
  27
  28 _LIBCPP_BEGIN_NAMESPACE_STD
  29
  30 template <class _AlgPolicy, class _Iter, class _Sent, class _Type, class _Proj, class _Comp>
  31 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
  32 _Iter __lower_bound(_Iter __first, _Sent __last, const _Type& __value, _Comp& __comp, _Proj& __proj) {
  33   auto __len = _IterOps<_AlgPolicy>::distance(__first, __last);
  34
  35   while (__len != 0) {
  36     auto __l2 = std::__half_positive(__len);
  37     _Iter __m = __first;
  38     _IterOps<_AlgPolicy>::advance(__m, __l2);
  39     if (std::__invoke(__comp, std::__invoke(__proj, *__m), __value)) {
  40       __first = ++__m;
  41       __len -= __l2 + 1;
  42     } else {
  43       __len = __l2;
  44     }
  45   }
  46   return __first;
  47 }
  48
  49 template <class _ForwardIterator, class _Tp, class _Compare>
  50 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
  51 _ForwardIterator lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value, _Compare __comp) {
  52   static_assert(__is_callable<_Compare, decltype(*__first), const _Tp&>::value,
  53                 "The comparator has to be callable");
  54   auto __proj = std::__identity();
  55   return std::__lower_bound<_ClassicAlgPolicy>(__first, __last, __value, __comp, __proj);
  56 }
  57
  58 template <class _ForwardIterator, class _Tp>
  59 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
  60 _ForwardIterator lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) {
  61   return std::lower_bound(__first, __last, __value, __less<>());
  62 }
  63
  64 _LIBCPP_END_NAMESPACE_STD
  65
  66 #endif // _LIBCPP___ALGORITHM_LOWER_BOUND_H