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 <__config> 14 #include <__functional/compose.h> 15 #include <__functional/invoke.h> 16 #include <__ranges/concepts.h> 17 #include <__utility/forward.h> 18 #include <__utility/move.h> 19 #include <concepts> 20 #include <type_traits> 21 22 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 23 # pragma GCC system_header 24 #endif 25 26 _LIBCPP_BEGIN_NAMESPACE_STD 27 28 #if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) 29 30 // CRTP base that one can derive from in order to be considered a range adaptor closure 31 // by the library. When deriving from this class, a pipe operator will be provided to 32 // make the following hold: 33 // - `x | f` is equivalent to `f(x)` 34 // - `f1 | f2` is an adaptor closure `g` such that `g(x)` is equivalent to `f2(f1(x))` 35 template <class _Tp> 36 struct __range_adaptor_closure; 37 38 // Type that wraps an arbitrary function object and makes it into a range adaptor closure, 39 // i.e. something that can be called via the `x | f` notation. 40 template <class _Fn> 41 struct __range_adaptor_closure_t : _Fn, __range_adaptor_closure<__range_adaptor_closure_t<_Fn>> { 42 constexpr explicit __range_adaptor_closure_t(_Fn&& __f) : _Fn(std::move(__f)) { } 43 }; 44 45 template <class _Tp> 46 concept _RangeAdaptorClosure = derived_from<remove_cvref_t<_Tp>, __range_adaptor_closure<remove_cvref_t<_Tp>>>; 47 48 template <class _Tp> 49 struct __range_adaptor_closure { 50 template <ranges::viewable_range _View, _RangeAdaptorClosure _Closure> 51 requires same_as<_Tp, remove_cvref_t<_Closure>> && 52 invocable<_Closure, _View> 53 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI 54 friend constexpr decltype(auto) operator|(_View&& __view, _Closure&& __closure) 55 noexcept(is_nothrow_invocable_v<_Closure, _View>) 56 { return std::invoke(std::forward<_Closure>(__closure), std::forward<_View>(__view)); } 57 58 template <_RangeAdaptorClosure _Closure, _RangeAdaptorClosure _OtherClosure> 59 requires same_as<_Tp, remove_cvref_t<_Closure>> && 60 constructible_from<decay_t<_Closure>, _Closure> && 61 constructible_from<decay_t<_OtherClosure>, _OtherClosure> 62 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI 63 friend constexpr auto operator|(_Closure&& __c1, _OtherClosure&& __c2) 64 noexcept(is_nothrow_constructible_v<decay_t<_Closure>, _Closure> && 65 is_nothrow_constructible_v<decay_t<_OtherClosure>, _OtherClosure>) 66 { return __range_adaptor_closure_t(std::__compose(std::forward<_OtherClosure>(__c2), std::forward<_Closure>(__c1))); } 67 }; 68 69 #endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) 70 71 _LIBCPP_END_NAMESPACE_STD 72 73 #endif // _LIBCPP___RANGES_RANGE_ADAPTOR_H 74