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 <iterator>
16 
17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
18 #pragma GCC system_header
19 #endif
20 
21 _LIBCPP_BEGIN_NAMESPACE_STD
22 
23 template <class _Compare, class _ForwardIterator, class _Tp>
24 _LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
25 __lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
26 {
27     typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
28     difference_type __len = _VSTD::distance(__first, __last);
29     while (__len != 0)
30     {
31         difference_type __l2 = _VSTD::__half_positive(__len);
32         _ForwardIterator __m = __first;
33         _VSTD::advance(__m, __l2);
34         if (__comp(*__m, __value_))
35         {
36             __first = ++__m;
37             __len -= __l2 + 1;
38         }
39         else
40             __len = __l2;
41     }
42     return __first;
43 }
44 
45 template <class _ForwardIterator, class _Tp, class _Compare>
46 _LIBCPP_NODISCARD_EXT inline
47 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
48 _ForwardIterator
49 lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_, _Compare __comp)
50 {
51     return _VSTD::__lower_bound<_Compare&>(__first, __last, __value_, __comp);
52 }
53 
54 template <class _ForwardIterator, class _Tp>
55 _LIBCPP_NODISCARD_EXT inline
56 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
57 _ForwardIterator
58 lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value_)
59 {
60     return _VSTD::lower_bound(__first, __last, __value_,
61                              __less<typename iterator_traits<_ForwardIterator>::value_type, _Tp>());
62 }
63 
64 _LIBCPP_END_NAMESPACE_STD
65 
66 #endif // _LIBCPP___ALGORITHM_LOWER_BOUND_H
67