1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP___RANGES_RANGE_ADAPTOR_H
11#define _LIBCPP___RANGES_RANGE_ADAPTOR_H
12
13#include <__concepts/constructible.h>
14#include <__concepts/derived_from.h>
15#include <__concepts/invocable.h>
16#include <__concepts/same_as.h>
17#include <__config>
18#include <__functional/compose.h>
19#include <__functional/invoke.h>
20#include <__ranges/concepts.h>
21#include <__type_traits/decay.h>
22#include <__type_traits/invoke.h>
23#include <__type_traits/is_class.h>
24#include <__type_traits/is_nothrow_constructible.h>
25#include <__type_traits/remove_cv.h>
26#include <__type_traits/remove_cvref.h>
27#include <__utility/forward.h>
28#include <__utility/move.h>
29
30#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
31# pragma GCC system_header
32#endif
33
34_LIBCPP_PUSH_MACROS
35#include <__undef_macros>
36
37_LIBCPP_BEGIN_NAMESPACE_STD
38
39#if _LIBCPP_STD_VER >= 20
40
41namespace ranges {
42
43// CRTP base that one can derive from in order to be considered a range adaptor closure
44// by the library. When deriving from this class, a pipe operator will be provided to
45// make the following hold:
46// - `x | f` is equivalent to `f(x)`
47// - `f1 | f2` is an adaptor closure `g` such that `g(x)` is equivalent to `f2(f1(x))`
48template <class _Tp>
49 requires is_class_v<_Tp> && same_as<_Tp, remove_cv_t<_Tp>>
50struct __range_adaptor_closure {};
51
52// Type that wraps an arbitrary function object and makes it into a range adaptor closure,
53// i.e. something that can be called via the `x | f` notation.
54template <class _Fn>
55struct __pipeable : _Fn, __range_adaptor_closure<__pipeable<_Fn>> {
56 _LIBCPP_HIDE_FROM_ABI constexpr explicit __pipeable(_Fn&& __f) : _Fn(std::move(__f)) {}
57};
58_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(__pipeable);
59
60template <class _Tp>
61_Tp __derived_from_range_adaptor_closure(__range_adaptor_closure<_Tp>*);
62
63template <class _Tp>
64concept _RangeAdaptorClosure = !ranges::range<remove_cvref_t<_Tp>> && requires {
65 // Ensure that `remove_cvref_t<_Tp>` is derived from `__range_adaptor_closure<remove_cvref_t<_Tp>>` and isn't derived
66 // from `__range_adaptor_closure<U>` for any other type `U`.
67 { ranges::__derived_from_range_adaptor_closure((remove_cvref_t<_Tp>*)nullptr) } -> same_as<remove_cvref_t<_Tp>>;
68};
69
70template <ranges::range _Range, _RangeAdaptorClosure _Closure>
71 requires invocable<_Closure, _Range>
72[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto)
73operator|(_Range&& __range, _Closure&& __closure) noexcept(is_nothrow_invocable_v<_Closure, _Range>) {
74 return std::invoke(std::forward<_Closure>(__closure), std::forward<_Range>(__range));
75}
76
77template <_RangeAdaptorClosure _Closure, _RangeAdaptorClosure _OtherClosure>
78 requires constructible_from<decay_t<_Closure>, _Closure> && constructible_from<decay_t<_OtherClosure>, _OtherClosure>
79[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator|(_Closure&& __c1, _OtherClosure&& __c2) noexcept(
80 is_nothrow_constructible_v<decay_t<_Closure>, _Closure> &&
81 is_nothrow_constructible_v<decay_t<_OtherClosure>, _OtherClosure>) {
82 return __pipeable(std::__compose(std::forward<_OtherClosure>(__c2), std::forward<_Closure>(__c1)));
83}
84
85# if _LIBCPP_STD_VER >= 23
86template <class _Tp>
87 requires is_class_v<_Tp> && same_as<_Tp, remove_cv_t<_Tp>>
88class _LIBCPP_NO_SPECIALIZATIONS range_adaptor_closure : public __range_adaptor_closure<_Tp> {};
89# endif // _LIBCPP_STD_VER >= 23
90
91} // namespace ranges
92
93#endif // _LIBCPP_STD_VER >= 20
94
95_LIBCPP_END_NAMESPACE_STD
96
97_LIBCPP_POP_MACROS
98
99#endif // _LIBCPP___RANGES_RANGE_ADAPTOR_H
100