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_nothrow_constructible.h> 23 #include <__type_traits/remove_cvref.h> 24 #include <__utility/forward.h> 25 #include <__utility/move.h> 26 27 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 28 # pragma GCC system_header 29 #endif 30 31 _LIBCPP_PUSH_MACROS 32 #include <__undef_macros> 33 34 _LIBCPP_BEGIN_NAMESPACE_STD 35 36 #if _LIBCPP_STD_VER >= 20 37 38 // CRTP base that one can derive from in order to be considered a range adaptor closure 39 // by the library. When deriving from this class, a pipe operator will be provided to 40 // make the following hold: 41 // - `x | f` is equivalent to `f(x)` 42 // - `f1 | f2` is an adaptor closure `g` such that `g(x)` is equivalent to `f2(f1(x))` 43 template <class _Tp> 44 struct __range_adaptor_closure; 45 46 // Type that wraps an arbitrary function object and makes it into a range adaptor closure, 47 // i.e. something that can be called via the `x | f` notation. 48 template <class _Fn> 49 struct __range_adaptor_closure_t : _Fn, __range_adaptor_closure<__range_adaptor_closure_t<_Fn>> { 50 _LIBCPP_HIDE_FROM_ABI constexpr explicit __range_adaptor_closure_t(_Fn&& __f) : _Fn(std::move(__f)) {} 51 }; 52 _LIBCPP_CTAD_SUPPORTED_FOR_TYPE(__range_adaptor_closure_t); 53 54 template <class _Tp> 55 concept _RangeAdaptorClosure = derived_from<remove_cvref_t<_Tp>, __range_adaptor_closure<remove_cvref_t<_Tp>>>; 56 57 template <class _Tp> 58 struct __range_adaptor_closure { 59 template <ranges::viewable_range _View, _RangeAdaptorClosure _Closure> 60 requires same_as<_Tp, remove_cvref_t<_Closure>> && invocable<_Closure, _View> 61 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI friend constexpr decltype(auto) 62 operator|(_View&& __view, _Closure&& __closure) noexcept(is_nothrow_invocable_v<_Closure, _View>) { 63 return std::invoke(std::forward<_Closure>(__closure), std::forward<_View>(__view)); 64 } 65 66 template <_RangeAdaptorClosure _Closure, _RangeAdaptorClosure _OtherClosure> 67 requires same_as<_Tp, remove_cvref_t<_Closure>> && constructible_from<decay_t<_Closure>, _Closure> && 68 constructible_from<decay_t<_OtherClosure>, _OtherClosure> 69 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI friend constexpr auto operator|(_Closure&& __c1, _OtherClosure&& __c2) noexcept( 70 is_nothrow_constructible_v<decay_t<_Closure>, _Closure> && 71 is_nothrow_constructible_v<decay_t<_OtherClosure>, _OtherClosure>) { 72 return __range_adaptor_closure_t(std::__compose(std::forward<_OtherClosure>(__c2), std::forward<_Closure>(__c1))); 73 } 74 }; 75 76 #endif // _LIBCPP_STD_VER >= 20 77 78 _LIBCPP_END_NAMESPACE_STD 79 80 _LIBCPP_POP_MACROS 81 82 #endif // _LIBCPP___RANGES_RANGE_ADAPTOR_H 83