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/is_class.h>
23#include <__type_traits/is_nothrow_constructible.h>
24#include <__type_traits/remove_cvref.h>
25#include <__utility/forward.h>
26#include <__utility/move.h>
27
28#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
29# pragma GCC system_header
30#endif
31
32_LIBCPP_PUSH_MACROS
33#include <__undef_macros>
34
35_LIBCPP_BEGIN_NAMESPACE_STD
36
37#if _LIBCPP_STD_VER >= 20
38
39namespace ranges {
40
41// CRTP base that one can derive from in order to be considered a range adaptor closure
42// by the library. When deriving from this class, a pipe operator will be provided to
43// make the following hold:
44// - `x | f` is equivalent to `f(x)`
45// - `f1 | f2` is an adaptor closure `g` such that `g(x)` is equivalent to `f2(f1(x))`
46template <class _Tp>
47 requires is_class_v<_Tp> && same_as<_Tp, remove_cv_t<_Tp>>
48struct __range_adaptor_closure;
49
50// Type that wraps an arbitrary function object and makes it into a range adaptor closure,
51// i.e. something that can be called via the `x | f` notation.
52template <class _Fn>
53struct __range_adaptor_closure_t : _Fn, __range_adaptor_closure<__range_adaptor_closure_t<_Fn>> {
54 _LIBCPP_HIDE_FROM_ABI constexpr explicit __range_adaptor_closure_t(_Fn&& __f) : _Fn(std::move(__f)) {}
55};
56_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(__range_adaptor_closure_t);
57
58template <class _Tp>
59_Tp __derived_from_range_adaptor_closure(__range_adaptor_closure<_Tp>*);
60
61template <class _Tp>
62concept _RangeAdaptorClosure = !ranges::range<remove_cvref_t<_Tp>> && requires {
63 // Ensure that `remove_cvref_t<_Tp>` is derived from `__range_adaptor_closure<remove_cvref_t<_Tp>>` and isn't derived
64 // from `__range_adaptor_closure<U>` for any other type `U`.
65 { ranges::__derived_from_range_adaptor_closure((remove_cvref_t<_Tp>*)nullptr) } -> same_as<remove_cvref_t<_Tp>>;
66};
67
68template <ranges::range _Range, _RangeAdaptorClosure _Closure>
69 requires invocable<_Closure, _Range>
70[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto)
71operator|(_Range&& __range, _Closure&& __closure) noexcept(is_nothrow_invocable_v<_Closure, _Range>) {
72 return std::invoke(std::forward<_Closure>(__closure), std::forward<_Range>(__range));
73}
74
75template <_RangeAdaptorClosure _Closure, _RangeAdaptorClosure _OtherClosure>
76 requires constructible_from<decay_t<_Closure>, _Closure> && constructible_from<decay_t<_OtherClosure>, _OtherClosure>
77[[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator|(_Closure&& __c1, _OtherClosure&& __c2) noexcept(
78 is_nothrow_constructible_v<decay_t<_Closure>, _Closure> &&
79 is_nothrow_constructible_v<decay_t<_OtherClosure>, _OtherClosure>) {
80 return __range_adaptor_closure_t(std::__compose(std::forward<_OtherClosure>(__c2), std::forward<_Closure>(__c1)));
81}
82
83template <class _Tp>
84 requires is_class_v<_Tp> && same_as<_Tp, remove_cv_t<_Tp>>
85struct __range_adaptor_closure {};
86
87# if _LIBCPP_STD_VER >= 23
88template <class _Tp>
89 requires is_class_v<_Tp> && same_as<_Tp, remove_cv_t<_Tp>>
90class range_adaptor_closure : public __range_adaptor_closure<_Tp> {};
91# endif // _LIBCPP_STD_VER >= 23
92
93} // namespace ranges
94
95#endif // _LIBCPP_STD_VER >= 20
96
97_LIBCPP_END_NAMESPACE_STD
98
99_LIBCPP_POP_MACROS
100
101#endif // _LIBCPP___RANGES_RANGE_ADAPTOR_H
102