P2387R3 Pipe for user defined range adaptors

stl/debugger/STL.natvis

@@ -619,6 +619,14 @@ SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
       </Expand>
   </Type>
 
+  <Type Name="std::_Back_binder&lt;*&gt;">
+    <DisplayString>bind_back({_Mypair}, {_Mypair._Myval2,view(noparens)})</DisplayString>
+    <Expand>
+      <Item Name="[f]">_Mypair</Item>
+      <Item Name="[bound_args]">_Mypair._Myval2</Item>
+    </Expand>
+  </Type>
+
 
   <!-- VC 2015 -->
   <Type Name="std::_Mem_fn&lt;*&gt;">

stl/inc/functional

@@ -2131,6 +2131,82 @@ _NODISCARD constexpr auto bind_front(_Fx&& _Func, _Types&&... _Args) {
 }
 #endif // _HAS_CXX20
 
+#if _HAS_CXX23
+template <size_t... _Ix, class _Cv_FD, class _Cv_tuple_TiD, class... _Unbound>
+constexpr auto _Call_back_binder(index_sequence<_Ix...>, _Cv_FD&& _Obj, _Cv_tuple_TiD&& _Tpl,
+    _Unbound&&... _Unbargs) noexcept(noexcept(_STD invoke(_STD forward<_Cv_FD>(_Obj),
+    _STD forward<_Unbound>(_Unbargs)..., _STD get<_Ix>(_STD forward<_Cv_tuple_TiD>(_Tpl))...)))
+    -> decltype(_STD invoke(_STD forward<_Cv_FD>(_Obj), _STD forward<_Unbound>(_Unbargs)...,
+        _STD get<_Ix>(_STD forward<_Cv_tuple_TiD>(_Tpl))...)) {
+    return _STD invoke(_STD forward<_Cv_FD>(_Obj), _STD forward<_Unbound>(_Unbargs)...,
+        _STD get<_Ix>(_STD forward<_Cv_tuple_TiD>(_Tpl))...);
+}
+
+template <class _Fx, class... _Types>
+class _Back_binder { // wrap bound callable object and arguments
+private:
+    using _Seq = index_sequence_for<_Types...>;
+
+    _Compressed_pair<_Fx, tuple<_Types...>> _Mypair;
+
+    _STL_INTERNAL_STATIC_ASSERT(is_same_v<_Fx, decay_t<_Fx>>);
+    _STL_INTERNAL_STATIC_ASSERT((is_same_v<_Types, decay_t<_Types>> && ...));
+
+public:
+    template <class _FxInit, class... _TypesInit,
+        enable_if_t<sizeof...(_TypesInit) != 0 || !is_same_v<remove_cvref_t<_FxInit>, _Back_binder>, int> = 0>
+    constexpr explicit _Back_binder(_FxInit&& _Func, _TypesInit&&... _Args)
+        : _Mypair(_One_then_variadic_args_t{}, _STD forward<_FxInit>(_Func), _STD forward<_TypesInit>(_Args)...) {}
+
+    template <class... _Unbound>
+    constexpr auto operator()(_Unbound&&... _Unbargs) & noexcept(
+        noexcept(_Call_back_binder(_Seq{}, _Mypair._Get_first(), _Mypair._Myval2, _STD forward<_Unbound>(_Unbargs)...)))
+        -> decltype(_Call_back_binder(
+            _Seq{}, _Mypair._Get_first(), _Mypair._Myval2, _STD forward<_Unbound>(_Unbargs)...)) {
+        return _Call_back_binder(_Seq{}, _Mypair._Get_first(), _Mypair._Myval2, _STD forward<_Unbound>(_Unbargs)...);
+    }
+
+    template <class... _Unbound>
+    constexpr auto operator()(_Unbound&&... _Unbargs) const& noexcept(
+        noexcept(_Call_back_binder(_Seq{}, _Mypair._Get_first(), _Mypair._Myval2, _STD forward<_Unbound>(_Unbargs)...)))
+        -> decltype(_Call_back_binder(
+            _Seq{}, _Mypair._Get_first(), _Mypair._Myval2, _STD forward<_Unbound>(_Unbargs)...)) {
+        return _Call_back_binder(_Seq{}, _Mypair._Get_first(), _Mypair._Myval2, _STD forward<_Unbound>(_Unbargs)...);
+    }
+
+    template <class... _Unbound>
+    constexpr auto operator()(_Unbound&&... _Unbargs) && noexcept(noexcept(_Call_back_binder(
+        _Seq{}, _STD move(_Mypair._Get_first()), _STD move(_Mypair._Myval2), _STD forward<_Unbound>(_Unbargs)...)))
+        -> decltype(_Call_back_binder(
+            _Seq{}, _STD move(_Mypair._Get_first()), _STD move(_Mypair._Myval2), _STD forward<_Unbound>(_Unbargs)...)) {
+        return _Call_back_binder(
+            _Seq{}, _STD move(_Mypair._Get_first()), _STD move(_Mypair._Myval2), _STD forward<_Unbound>(_Unbargs)...);
+    }
+
+    template <class... _Unbound>
+    constexpr auto operator()(_Unbound&&... _Unbargs) const&& noexcept(noexcept(_Call_back_binder(
+        _Seq{}, _STD move(_Mypair._Get_first()), _STD move(_Mypair._Myval2), _STD forward<_Unbound>(_Unbargs)...)))
+        -> decltype(_Call_back_binder(
+            _Seq{}, _STD move(_Mypair._Get_first()), _STD move(_Mypair._Myval2), _STD forward<_Unbound>(_Unbargs)...)) {
+        return _Call_back_binder(
+            _Seq{}, _STD move(_Mypair._Get_first()), _STD move(_Mypair._Myval2), _STD forward<_Unbound>(_Unbargs)...);
+    }
+};
+template <class _Fx, class... _Types>
+_NODISCARD constexpr auto bind_back(_Fx&& _Func, _Types&&... _Args) {
+    static_assert(is_constructible_v<decay_t<_Fx>, _Fx>,
+        "std::bind_back requires the decayed callable to be constructible from an undecayed callable");
+    static_assert(
+        is_move_constructible_v<decay_t<_Fx>>, "std::bind_back requires the decayed callable to be move constructible");
+    static_assert(conjunction_v<is_constructible<decay_t<_Types>, _Types>...>,
+        "std::bind_back requires the decayed bound arguments to be constructible from undecayed bound arguments");
+    static_assert(conjunction_v<is_move_constructible<decay_t<_Types>>...>,
+        "std::bind_back requires the decayed bound arguments to be move constructible");
+
+    return _Back_binder<decay_t<_Fx>, decay_t<_Types>...>(_STD forward<_Fx>(_Func), _STD forward<_Types>(_Args)...);
+}
+#endif // _HAS_CXX23
+
 #if _HAS_FUNCTION_ALLOCATOR_SUPPORT
 template <class _Fty, class _Alloc>
 struct uses_allocator<function<_Fty>, _Alloc> : true_type {}; // true_type if container allocator enabled

stl/inc/ranges

@@ -61,108 +61,80 @@ namespace ranges {
     using _Maybe_wrapped = conditional_t<_IsWrapped, _Ty, _Unwrapped_t<_Ty>>;
 
     namespace _Pipe {
-        // clang-format off
-        template <class _Left, class _Right>
-        concept _Can_pipe = requires(_Left&& __l, _Right&& __r) {
-            static_cast<_Right&&>(__r)(static_cast<_Left&&>(__l));
-        };
-
-        template <class _Left, class _Right>
-        concept _Can_compose = constructible_from<remove_cvref_t<_Left>, _Left>
-            && constructible_from<remove_cvref_t<_Right>, _Right>;
-        // clang-format on
-
-        template <class, class>
-        struct _Pipeline;
-
         template <class _Derived>
-        struct _Base {
-            template <class _Other>
-                requires _Can_compose<_Derived, _Other>
-            constexpr auto operator|(_Base<_Other>&& __r) && noexcept(
-                noexcept(_Pipeline{static_cast<_Derived&&>(*this), static_cast<_Other&&>(__r)})) {
-                _STL_INTERNAL_STATIC_ASSERT(derived_from<_Derived, _Base<_Derived>>);
-                _STL_INTERNAL_STATIC_ASSERT(derived_from<_Other, _Base<_Other>>);
-                return _Pipeline{static_cast<_Derived&&>(*this), static_cast<_Other&&>(__r)};
-            }
-
-            template <class _Other>
-                requires _Can_compose<_Derived, const _Other&>
-            constexpr auto operator|(const _Base<_Other>& __r) && noexcept(
-                noexcept(_Pipeline{static_cast<_Derived&&>(*this), static_cast<const _Other&>(__r)})) {
-                _STL_INTERNAL_STATIC_ASSERT(derived_from<_Derived, _Base<_Derived>>);
-                _STL_INTERNAL_STATIC_ASSERT(derived_from<_Other, _Base<_Other>>);
-                return _Pipeline{static_cast<_Derived&&>(*this), static_cast<const _Other&>(__r)};
-            }
-
-            template <class _Other>
-                requires _Can_compose<const _Derived&, _Other>
-            constexpr auto operator|(_Base<_Other>&& __r) const& noexcept(
-                noexcept(_Pipeline{static_cast<const _Derived&>(*this), static_cast<_Other&&>(__r)})) {
-                _STL_INTERNAL_STATIC_ASSERT(derived_from<_Derived, _Base<_Derived>>);
-                _STL_INTERNAL_STATIC_ASSERT(derived_from<_Other, _Base<_Other>>);
-                return _Pipeline{static_cast<const _Derived&>(*this), static_cast<_Other&&>(__r)};
-            }
-
-            template <class _Other>
-                requires _Can_compose<const _Derived&, const _Other&>
-            constexpr auto operator|(const _Base<_Other>& __r) const& noexcept(
-                noexcept(_Pipeline{static_cast<const _Derived&>(*this), static_cast<const _Other&>(__r)})) {
-                _STL_INTERNAL_STATIC_ASSERT(derived_from<_Derived, _Base<_Derived>>);
-                _STL_INTERNAL_STATIC_ASSERT(derived_from<_Other, _Base<_Other>>);
-                return _Pipeline{static_cast<const _Derived&>(*this), static_cast<const _Other&>(__r)};
-            }
-
-            template <_Can_pipe<const _Derived&> _Left>
-            friend constexpr auto operator|(_Left&& __l, const _Base& __r)
-#ifdef __EDG__ // TRANSITION, VSO-1222776
-                noexcept(noexcept(_STD declval<const _Derived&>()(_STD forward<_Left>(__l))))
-#else // ^^^ workaround / no workaround vvv
-                noexcept(noexcept(static_cast<const _Derived&>(__r)(_STD forward<_Left>(__l))))
-#endif // TRANSITION, VSO-1222776
-            {
-                return static_cast<const _Derived&>(__r)(_STD forward<_Left>(__l));
-            }
+        struct _Base {};
 
-            template <_Can_pipe<_Derived> _Left>
-            friend constexpr auto operator|(_Left&& __l, _Base&& __r)
-#ifdef __EDG__ // TRANSITION, VSO-1222776
-                noexcept(noexcept(_STD declval<_Derived>()(_STD forward<_Left>(__l))))
-#else // ^^^ workaround / no workaround vvv
-                noexcept(noexcept(static_cast<_Derived&&>(__r)(_STD forward<_Left>(__l))))
-#endif // TRANSITION, VSO-1222776
-            {
-                return static_cast<_Derived&&>(__r)(_STD forward<_Left>(__l));
-            }
+        template <class _Ty>
+        _Ty* _Derived_from_range_adaptor_closure(_Base<_Ty>&); // not defined
+
+        template <class _Ty>
+        concept _Range_adaptor_closure_object = !range<remove_cvref_t<_Ty>> && requires(remove_cvref_t<_Ty> & __t) {
+            { _Pipe::_Derived_from_range_adaptor_closure(__t) } -> same_as<remove_cvref_t<_Ty>*>;
         };
 
-        template <class _Left, class _Right>
-        struct _Pipeline : _Base<_Pipeline<_Left, _Right>> {
-            /* [[no_unique_address]] */ _Left __l;
-            /* [[no_unique_address]] */ _Right __r;
+        template <class _ClosureLeft, class _ClosureRight>
+        struct _Pipeline : _Base<_Pipeline<_ClosureLeft, _ClosureRight>> {
+            _STL_INTERNAL_STATIC_ASSERT(_Range_adaptor_closure_object<_ClosureLeft>);
+            _STL_INTERNAL_STATIC_ASSERT(_Range_adaptor_closure_object<_ClosureRight>);
+
+            /* [[no_unique_address]] */ _ClosureLeft _Left;
+            /* [[no_unique_address]] */ _ClosureRight _Right;
 
             template <class _Ty1, class _Ty2>
             constexpr explicit _Pipeline(_Ty1&& _Val1, _Ty2&& _Val2) noexcept(
-                is_nothrow_convertible_v<_Ty1, _Left>&& is_nothrow_convertible_v<_Ty2, _Right>)
-                : __l(_STD forward<_Ty1>(_Val1)), __r(_STD forward<_Ty2>(_Val2)) {}
+                is_nothrow_constructible_v<_Ty1, _ClosureLeft>&& is_nothrow_constructible_v<_Ty2, _ClosureRight>)
+                : _Left(_STD forward<_Ty1>(_Val1)), _Right(_STD forward<_Ty2>(_Val2)) {}
 
             template <class _Ty>
-            _NODISCARD constexpr auto operator()(_Ty&& _Val) noexcept(
-                noexcept(__r(__l(_STD forward<_Ty>(_Val))))) requires requires {
-                __r(__l(static_cast<_Ty&&>(_Val)));
+            _NODISCARD constexpr auto operator()(_Ty&& _Val) & noexcept(
+                noexcept(_Right(_Left(_STD forward<_Ty>(_Val))))) requires requires {
+                _Right(_Left(_STD forward<_Ty>(_Val)));
             }
-            { return __r(__l(_STD forward<_Ty>(_Val))); }
+            { return _Right(_Left(_STD forward<_Ty>(_Val))); }
 
             template <class _Ty>
-            _NODISCARD constexpr auto operator()(_Ty&& _Val) const
-                noexcept(noexcept(__r(__l(_STD forward<_Ty>(_Val))))) requires requires {
-                __r(__l(static_cast<_Ty&&>(_Val)));
+            _NODISCARD constexpr auto operator()(_Ty&& _Val) const& noexcept(
+                noexcept(_Right(_Left(_STD forward<_Ty>(_Val))))) requires requires {
+                _Right(_Left(_STD forward<_Ty>(_Val)));
             }
-            { return __r(__l(_STD forward<_Ty>(_Val))); }
+            { return _Right(_Left(_STD forward<_Ty>(_Val))); }
+
+            template <class _Ty>
+            _NODISCARD constexpr auto operator()(_Ty&& _Val) && noexcept(
+                noexcept(_STD move(_Right)(_STD move(_Left)(_STD forward<_Ty>(_Val))))) requires requires {
+                _STD move(_Right)(_STD move(_Left)(_STD forward<_Ty>(_Val)));
+            }
+            { return _STD move(_Right)(_STD move(_Left)(_STD forward<_Ty>(_Val))); }
+
+            template <class _Ty>
+            _NODISCARD constexpr auto operator()(_Ty&& _Val) const&& noexcept(
+                noexcept(_STD move(_Right)(_STD move(_Left)(_STD forward<_Ty>(_Val))))) requires requires {
+                _STD move(_Right)(_STD move(_Left)(_STD forward<_Ty>(_Val)));
+            }
+            { return _STD move(_Right)(_STD move(_Left)(_STD forward<_Ty>(_Val))); }
         };
 
         template <class _Ty1, class _Ty2>
         _Pipeline(_Ty1, _Ty2) -> _Pipeline<_Ty1, _Ty2>;
+
+        template <class _Left, class _Right>
+            requires _Range_adaptor_closure_object<_Left> //
+                && _Range_adaptor_closure_object<_Right> //
+                && constructible_from<remove_cvref_t<_Left>, _Left> //
+                && constructible_from<remove_cvref_t<_Right>, _Right>
+        constexpr auto operator|(_Left&& __l, _Right&& __r) noexcept(
+            noexcept(_Pipeline{static_cast<_Left&&>(__l), static_cast<_Right&&>(__r)})) {
+            return _Pipeline{static_cast<_Left&&>(__l), static_cast<_Right&&>(__r)};
+        }
+
+        template <class _Left, class _Right>
+            requires _Range_adaptor_closure_object<_Right> && range<_Left>
+        constexpr auto operator|(_Left&& __l, _Right&& __r) noexcept(
+            noexcept(_STD forward<_Right>(__r)(_STD forward<_Left>(__l)))) //
+            requires requires {
+            static_cast<_Right&&>(__r)(static_cast<_Left&&>(__l));
+        }
+        { return _STD forward<_Right>(__r)(_STD forward<_Left>(__l)); }
     } // namespace _Pipe
 
     template <range _Rng, class _Derived>
@@ -805,6 +777,13 @@ namespace ranges {
         };
     };
 
+#if _HAS_CXX23
+    template <class _Derived>
+        requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>>
+    class range_adaptor_closure : public _Pipe::_Base<_Derived> {
+    };
+#endif
+
     template <class _Fn, class... _Types>
     class _Range_closure : public _Pipe::_Base<_Range_closure<_Fn, _Types...>> {
     public:
@@ -4289,7 +4268,6 @@ namespace ranges {
                 }
             }
 
-
         public:
             using iterator_concept = typename _Outer_iter<_Const>::iterator_concept;
             using value_type       = range_value_t<_BaseTy>;
@@ -4506,7 +4484,7 @@ namespace ranges {
 #else // ^^^ no workaround / workaround vvv
                 auto _Match = _RANGES search(subrange{_Current, _Last}, _Parent->_Pattern);
                 auto _Begin = _Match.begin();
-                auto _End = _Match.end();
+                auto _End   = _Match.end();
 #endif // TRANSITION, DevCom-1559808
                 if (_Begin != _Last && _RANGES empty(_Parent->_Pattern)) {
                     ++_Begin;
@@ -4558,7 +4536,7 @@ namespace ranges {
 #else // ^^^ no workaround / workaround vvv
             auto _Match = _RANGES search(subrange{_It, _Last}, _Pattern);
             auto _Begin = _Match.begin();
-            auto _End = _Match.end();
+            auto _End   = _Match.end();
 #endif // TRANSITION, DevCom-1559808
             if (_Begin != _Last && _RANGES empty(_Pattern)) {
                 ++_Begin;
@@ -5086,7 +5064,7 @@ namespace ranges {
                 (void) _Off;
 #else // ^^^ _ITERATOR_DEBUG_LEVEL == 0 / _ITERATOR_DEBUG_LEVEL != 0 vvv
                 if constexpr (_Offset_verifiable_v<iterator_t<_Base>>) {
-                    _Current._Verify_offset(_Off);
+                      _Current._Verify_offset(_Off);
                 }
 #endif // _ITERATOR_DEBUG_LEVEL == 0
             }

stl/inc/yvals_core.h

@@ -323,6 +323,7 @@
 // P2302R4 ranges::contains, ranges::contains_subrange
 // P2321R2 zip
 //     (changes to pair, tuple, and vector<bool>::reference only)
+// P2387R3 Pipe Support For User-Defined Range Adaptors
 // P2417R2 More constexpr bitset
 // P2440R1 ranges::iota, ranges::shift_left, ranges::shift_right
 // P2441R2 views::join_with
@@ -1459,10 +1460,6 @@ _EMIT_STL_ERROR(STL1004, "C++98 unexpected() is incompatible with C++23 unexpect
 
 #define __cpp_lib_polymorphic_allocator 201902L
 
-#ifdef __cpp_lib_concepts // TRANSITION, GH-395
-#define __cpp_lib_ranges 202110L
-#endif // __cpp_lib_concepts
-
 #define __cpp_lib_remove_cvref            201711L
 #define __cpp_lib_semaphore               201907L
 #define __cpp_lib_smart_ptr_for_overwrite 202002L
@@ -1495,6 +1492,7 @@ _EMIT_STL_ERROR(STL1004, "C++98 unexpected() is incompatible with C++23 unexpect
 #endif // __cpp_lib_concepts
 
 #define __cpp_lib_associative_heterogeneous_erasure 202110L
+#define __cpp_lib_bind_back                         202202L
 #define __cpp_lib_byteswap                          202110L
 #define __cpp_lib_constexpr_bitset                  202207L
 #define __cpp_lib_constexpr_typeinfo                202106L
@@ -1569,6 +1567,14 @@ _EMIT_STL_ERROR(STL1004, "C++98 unexpected() is incompatible with C++23 unexpect
 #define __cpp_lib_optional 201606L // P0307R2 Making Optional Greater Equal Again
 #endif // _HAS_CXX17
 
+#if defined(__cpp_lib_concepts) // TRANSITION, GH-395
+#if _HAS_CXX23
+#define __cpp_lib_ranges 202202L // P2387R3 Pipe Support For User-Defined Range Adaptors
+#elif _HAS_CXX20 // ^^^ _HAS_CXX23 / _HAS_CXX20 vvv
+#define __cpp_lib_ranges 202110L // P2415R2 What Is A `view`?
+#endif // _HAS_CXX20
+#endif // defined(__cpp_lib_concepts)
+
 #if _HAS_CXX20
 #define __cpp_lib_shared_ptr_arrays 201707L // P0674R1 make_shared() For Arrays
 #else // _HAS_CXX20

tests/std/test.lst

@@ -543,6 +543,8 @@ tests\P2273R3_constexpr_unique_ptr
 tests\P2302R4_ranges_alg_contains
 tests\P2302R4_ranges_alg_contains_subrange
 tests\P2321R2_proxy_reference
+tests\P2387R3_bind_back
+tests\P2387R3_pipe_support_for_user_defined_range_adaptors
 tests\P2401R0_conditional_noexcept_for_exchange
 tests\P2408R5_ranges_iterators_to_classic_algorithms
 tests\P2415R2_owning_view

tests/std/tests/P2387R3_bind_back/env.lst

@@ -0,0 +1,4 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+RUNALL_INCLUDE ..\usual_latest_matrix.lst