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_RANGES_MIN_ELEMENT_H
10 #define _LIBCPP___ALGORITHM_RANGES_MIN_ELEMENT_H
11 
12 #include <__config>
13 #include <__functional/identity.h>
14 #include <__functional/invoke.h>
15 #include <__functional/ranges_operations.h>
16 #include <__iterator/concepts.h>
17 #include <__iterator/projected.h>
18 #include <__ranges/access.h>
19 #include <__ranges/concepts.h>
20 #include <__ranges/dangling.h>
21 #include <__utility/forward.h>
22 
23 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
24 #  pragma GCC system_header
25 #endif
26 
27 #if _LIBCPP_STD_VER >= 20
28 
29 _LIBCPP_BEGIN_NAMESPACE_STD
30 
31 namespace ranges {
32 
33 // TODO(ranges): `ranges::min_element` can now simply delegate to `std::__min_element`.
34 template <class _Ip, class _Sp, class _Proj, class _Comp>
35 _LIBCPP_HIDE_FROM_ABI constexpr _Ip __min_element_impl(_Ip __first, _Sp __last, _Comp& __comp, _Proj& __proj) {
36   if (__first == __last)
37     return __first;
38 
39   _Ip __i = __first;
40   while (++__i != __last)
41     if (std::invoke(__comp, std::invoke(__proj, *__i), std::invoke(__proj, *__first)))
42       __first = __i;
43   return __first;
44 }
45 
46 namespace __min_element {
47 struct __fn {
48   template <forward_iterator _Ip,
49             sentinel_for<_Ip> _Sp,
50             class _Proj                                             = identity,
51             indirect_strict_weak_order<projected<_Ip, _Proj>> _Comp = ranges::less>
52   _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr _Ip
53   operator()(_Ip __first, _Sp __last, _Comp __comp = {}, _Proj __proj = {}) const {
54     return ranges::__min_element_impl(__first, __last, __comp, __proj);
55   }
56 
57   template <forward_range _Rp,
58             class _Proj                                                         = identity,
59             indirect_strict_weak_order<projected<iterator_t<_Rp>, _Proj>> _Comp = ranges::less>
60   _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr borrowed_iterator_t<_Rp>
61   operator()(_Rp&& __r, _Comp __comp = {}, _Proj __proj = {}) const {
62     return ranges::__min_element_impl(ranges::begin(__r), ranges::end(__r), __comp, __proj);
63   }
64 };
65 } // namespace __min_element
66 
67 inline namespace __cpo {
68 inline constexpr auto min_element = __min_element::__fn{};
69 } // namespace __cpo
70 } // namespace ranges
71 
72 _LIBCPP_END_NAMESPACE_STD
73 
74 #endif // _LIBCPP_STD_VER >= 20
75 
76 #endif // _LIBCPP___ALGORITHM_RANGES_MIN_ELEMENT_H
77