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 <__config>
15 #include <__functional/identity.h>
16 #include <__type_traits/is_callable.h>
17 #include <iterator>
18 
19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20 #  pragma GCC system_header
21 #endif
22 
23 _LIBCPP_BEGIN_NAMESPACE_STD
24 
25 template <class _Iter, class _Sent, class _Type, class _Proj, class _Comp>
26 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17
27 _Iter __lower_bound_impl(_Iter __first, _Sent __last, const _Type& __value, _Comp& __comp, _Proj& __proj) {
28   auto __len = std::__ranges_distance(__first, __last);
29 
30   while (__len != 0) {
31     auto __l2 = std::__half_positive(__len);
32     _Iter __m = __first;
33     std::__ranges_advance(__m, __l2);
34     if (std::__invoke(__comp, std::__invoke(__proj, *__m), __value)) {
35       __first = ++__m;
36       __len -= __l2 + 1;
37     } else {
38       __len = __l2;
39     }
40   }
41   return __first;
42 }
43 
44 template <class _ForwardIterator, class _Tp, class _Compare>
45 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17
46 _ForwardIterator lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp) {
47   static_assert(__is_callable<_Compare, decltype(*__first), const _Tp&>::value,
48                 "The comparator has to be callable");
49   auto __proj = std::__identity();
50   return std::__lower_bound_impl(__first, __last, __value_, __comp, __proj);
51 }
52 
53 template <class _ForwardIterator, class _Tp>
54 _LIBCPP_NODISCARD_EXT inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17
55 _ForwardIterator lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_) {
56   return std::lower_bound(__first, __last, __value_,
57                           __less<typename iterator_traits<_ForwardIterator>::value_type, _Tp>());
58 }
59 
60 _LIBCPP_END_NAMESPACE_STD
61 
62 #endif // _LIBCPP___ALGORITHM_LOWER_BOUND_H
63