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[libc++][numeric] P0543R3: Saturation arithmetic
Implements: https://wg21.link/P0543R3 - https://eel.is/c++draft/numeric.sat Additional notes: - Division: https://eel.is/c++draft/expr.mul#4 - Arithmetic conversions: https://eel.is/c++draft/expr.arith.conv#1.5 - Clang builtins: https://clang.llvm.org/docs/LanguageExtensions.html#builtin-functions
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‎libcxx/docs/FeatureTestMacroTable.rst

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@@ -432,7 +432,7 @@ Status
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--------------------------------------------------- -----------------
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``__cpp_lib_rcu`` *unimplemented*
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--------------------------------------------------- -----------------
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``__cpp_lib_saturation_arithmetic`` *unimplemented*
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``__cpp_lib_saturation_arithmetic`` ``202311L``
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--------------------------------------------------- -----------------
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``__cpp_lib_smart_ptr_owner_equality`` *unimplemented*
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--------------------------------------------------- -----------------

‎libcxx/docs/ReleaseNotes/18.rst

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@@ -54,12 +54,13 @@ Implemented Papers
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- P2905R2 - Runtime format strings
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- P2918R2 - Runtime format strings II
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- P2871R3 - Remove Deprecated Unicode Conversion Facets from C++26
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- P2870R3 - Remove basic_string::reserve()
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- P2870R3 - Remove ``basic_string::reserve()``
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- P2909R4 - Fix formatting of code units as integers (Dude, where’s my ``char``?)
59-
- P2821R5 - span.at()
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- P0521R0 - Proposed Resolution for CA 14 (shared_ptr use_count/unique)
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- P2821R5 - ``span.at()``
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- P0521R0 - Proposed Resolution for CA 14 (``shared_ptr`` ``use_count/unique``)
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- P1759R6 - Native handles and file streams
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- P2517R1 - Add a conditional ``noexcept`` specification to ``std::apply``
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- P0543R3 - Saturation arithmetic
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Improvements and New Features

‎libcxx/docs/Status/Cxx2cPapers.csv

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"`P2714R1 <https://wg21.link/P2714R1>`__","LWG","Bind front and back to NTTP callables","Varna June 2023","","",""
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"`P2630R4 <https://wg21.link/P2630R4>`__","LWG","``submdspan``","Varna June 2023","","",""
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"","","","","","",""
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"`P0543R3 <https://wg21.link/P0543R3>`__","LWG","Saturation arithmetic","Kona November 2023","","",""
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"`P0543R3 <https://wg21.link/P0543R3>`__","LWG","Saturation arithmetic","Kona November 2023","|Complete|","18.0",""
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"`P2407R5 <https://wg21.link/P2407R5>`__","LWG","Freestanding Library: Partial Classes","Kona November 2023","","",""
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"`P2546R5 <https://wg21.link/P2546R5>`__","LWG","Debugging Support","Kona November 2023","","",""
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"`P2905R2 <https://wg21.link/P2905R2>`__","LWG","Runtime format strings","Kona November 2023","|Complete|","18.0","|format| |DR|"

‎libcxx/include/CMakeLists.txt

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__numeric/pstl_reduce.h
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__numeric/pstl_transform_reduce.h
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__numeric/reduce.h
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__numeric/saturation_arithmetic.h
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__numeric/transform_exclusive_scan.h
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__numeric/transform_inclusive_scan.h
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__numeric/transform_reduce.h

‎libcxx/include/__numeric/saturation_arithmetic.h

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// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___NUMERIC_SATURATION_ARITHMETIC_H
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#define _LIBCPP___NUMERIC_SATURATION_ARITHMETIC_H
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#include <__concepts/arithmetic.h>
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#include <__config>
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#include <__type_traits/decay.h>
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#include <__utility/cmp.h>
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#include <limits>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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#if _LIBCPP_STD_VER >= 26
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template <typename _Tp>
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// concept __libcpp_standard_integer = __libcpp_unsigned_integer<_Tp> || __libcpp_signed_integer<_Tp>;
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// concept __libcpp_standard_integer =
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// __libcpp_unsigned_integer<remove_cv<_Tp>> || __libcpp_signed_integer<remove_cv<_Tp>>;
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concept __libcpp_standard_integer = __libcpp_unsigned_integer<decay_t<_Tp>> || __libcpp_signed_integer<decay_t<_Tp>>;
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template <__libcpp_standard_integer _Tp>
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// requires __libcpp_standard_integer<_Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp add_sat(_Tp __x, _Tp __y) noexcept {
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// builtins: clang/docs/LanguageExtensions.rst
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// builtins:
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// https://github.com/llvm/llvm-project/blob/7b45c549670a8e8b6fe90f4382b0699dd20707d3/clang/docs/LanguageExtensions.rst#L3500
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if (_Tp __sum; !__builtin_add_overflow(__x, __y, &__sum))
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return __sum;
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// Handle overflow
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if constexpr (__libcpp_unsigned_integer<_Tp>) {
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return std::numeric_limits<_Tp>::max();
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} else {
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// Signed addition overflow
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if (__x > 0)
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// Overflows if (x > 0 && y > 0)
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return std::numeric_limits<_Tp>::max();
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else
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// Overflows if (x < 0 && y < 0)
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return std::numeric_limits<_Tp>::min();
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}
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}
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template <__libcpp_standard_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp sub_sat(_Tp __x, _Tp __y) noexcept {
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if (_Tp __sub; !__builtin_sub_overflow(__x, __y, &__sub))
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return __sub;
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// Handle overflow
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if constexpr (__libcpp_unsigned_integer<_Tp>) {
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// Overflows if (x < y)
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return std::numeric_limits<_Tp>::min();
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} else {
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// Signed subtration overflow
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if (__x > 0)
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// Overflows if (x > 0 && y < 0)
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return std::numeric_limits<_Tp>::max();
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else
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// Overflows if (x < 0 && y > 0)
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return std::numeric_limits<_Tp>::min();
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}
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}
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template <__libcpp_standard_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp mul_sat(_Tp __x, _Tp __y) noexcept {
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if (_Tp __mul; !__builtin_mul_overflow(__x, __y, &__mul))
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return __mul;
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// Handle overflow
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if constexpr (__libcpp_unsigned_integer<_Tp>) {
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return std::numeric_limits<_Tp>::max();
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} else {
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// Signed multiplication overflow
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// if (__x > 0 && __y > 0)
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// // Overflows if (x > 0 && y > 0)
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// return std::numeric_limits<_Tp>::max();
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// else if (__y > 0)
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// // Overflows if (x > 0 && y < 0)
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// return std::numeric_limits<_Tp>::max();
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if (__x > 0) {
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if (__y > 0)
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// Overflows if (x > 0 && y > 0)
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return std::numeric_limits<_Tp>::max();
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// Overflows if (x > 0 && y < 0)
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return std::numeric_limits<_Tp>::min();
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}
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if (__y > 0)
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// Overflows if (x < 0 && y > 0)
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return std::numeric_limits<_Tp>::min();
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// Overflows if (x < 0 && y < 0)
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return std::numeric_limits<_Tp>::max();
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}
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}
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template <__libcpp_standard_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Tp div_sat(_Tp __x, _Tp __y) noexcept {
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_LIBCPP_ASSERT_UNCATEGORIZED(__y != 0, "Division by 0 is undefined");
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if constexpr (__libcpp_unsigned_integer<_Tp>) {
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return __x / __y;
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} else {
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// Handle signed division overflow
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if (__x == std::numeric_limits<_Tp>::min() && __y == _Tp{-1})
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return std::numeric_limits<_Tp>::max();
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return __x / __y;
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}
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}
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template <__libcpp_standard_integer _Rp, __libcpp_standard_integer _Tp>
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_LIBCPP_HIDE_FROM_ABI constexpr _Rp saturate_cast(_Tp __x) noexcept {
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// if (std::in_range<_Rp>(__x)) {
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// return _Rp{__x};
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// }
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// Handle overflow
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if (std::cmp_less_equal(__x, std::numeric_limits<_Rp>::min()))
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return std::numeric_limits<_Rp>::min();
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if (std::cmp_greater_equal(__x, std::numeric_limits<_Rp>::max()))
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return std::numeric_limits<_Rp>::max();
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// No overflow
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return static_cast<_Rp>(__x);
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}
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#endif // _LIBCPP_STD_VER >= 26
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___NUMERIC_SATURATION_ARITHMETIC_H

‎libcxx/include/module.modulemap.in

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export *
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}
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module std_private_numeric_reduce [system] { header "__numeric/reduce.h" }
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module std_private_numeric_saturation_arithmetic [system] { header "__numeric/saturation_arithmetic.h" }
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module std_private_numeric_transform_exclusive_scan [system] { header "__numeric/transform_exclusive_scan.h" }
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module std_private_numeric_transform_inclusive_scan [system] { header "__numeric/transform_inclusive_scan.h" }
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module std_private_numeric_transform_reduce [system] { header "__numeric/transform_reduce.h" }

‎libcxx/include/numeric

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template<class T>
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constexpr T* midpoint(T* a, T* b); // C++20
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// [numeric.sat], saturation arithmetic
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template<class T>
145+
constexpr T add_sat(T x, T y) noexcept; // freestanding, Since C++26
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template<class T>
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constexpr T sub_sat(T x, T y) noexcept; // freestanding, Since C++26
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template<class T>
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constexpr T mul_sat(T x, T y) noexcept; // freestanding, Since C++26
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template<class T>
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constexpr T div_sat(T x, T y) noexcept; // freestanding, Since C++26
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template<class T, class U>
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constexpr T saturate_cast(U x) noexcept; // freestanding, Since C++26
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} // std
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*/
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#include <__numeric/pstl_reduce.h>
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#include <__numeric/pstl_transform_reduce.h>
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#include <__numeric/reduce.h>
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#include <__numeric/saturation_arithmetic.h>
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#include <__numeric/transform_exclusive_scan.h>
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#include <__numeric/transform_inclusive_scan.h>
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#include <__numeric/transform_reduce.h>

‎libcxx/include/version

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// # define __cpp_lib_out_ptr 202311L
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# define __cpp_lib_ratio 202306L
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// # define __cpp_lib_rcu 202306L
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// # define __cpp_lib_saturation_arithmetic 202311L
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# define __cpp_lib_saturation_arithmetic 202311L
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// # define __cpp_lib_smart_ptr_owner_equality 202306L
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# define __cpp_lib_span_at 202311L
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// # define __cpp_lib_span_initializer_list 202311L

‎libcxx/modules/std/numeric.inc

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// [numeric.ops.midpoint], midpoint
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using std::midpoint;
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#if _LIBCPP_STD_VER >= 26
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// [numeric.sat], saturation arithmetic
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using std::add_sat;
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using std::sub_sat;
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using std::mul_sat;
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using std::div_sat;
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using std::saturate_cast;
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#endif
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} // namespace std

‎libcxx/test/std/language.support/support.limits/support.limits.general/numeric.version.compile.pass.cpp

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# endif
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# endif
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266-
# if !defined(_LIBCPP_VERSION)
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# ifndef __cpp_lib_saturation_arithmetic
268-
# error "__cpp_lib_saturation_arithmetic should be defined in c++26"
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# endif
270-
# if __cpp_lib_saturation_arithmetic != 202311L
271-
# error "__cpp_lib_saturation_arithmetic should have the value 202311L in c++26"
272-
# endif
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# else // _LIBCPP_VERSION
274-
# ifdef __cpp_lib_saturation_arithmetic
275-
# error "__cpp_lib_saturation_arithmetic should not be defined because it is unimplemented in libc++!"
276-
# endif
266+
# ifndef __cpp_lib_saturation_arithmetic
267+
# error "__cpp_lib_saturation_arithmetic should be defined in c++26"
268+
# endif
269+
# if __cpp_lib_saturation_arithmetic != 202311L
270+
# error "__cpp_lib_saturation_arithmetic should have the value 202311L in c++26"
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# endif
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#endif // TEST_STD_VER > 23

‎libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp

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# error "__cpp_lib_sample should have the value 201603L in c++26"
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# endif
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# if !defined(_LIBCPP_VERSION)
7171-
# ifndef __cpp_lib_saturation_arithmetic
7172-
# error "__cpp_lib_saturation_arithmetic should be defined in c++26"
7173-
# endif
7174-
# if __cpp_lib_saturation_arithmetic != 202311L
7175-
# error "__cpp_lib_saturation_arithmetic should have the value 202311L in c++26"
7176-
# endif
7177-
# else // _LIBCPP_VERSION
7178-
# ifdef __cpp_lib_saturation_arithmetic
7179-
# error "__cpp_lib_saturation_arithmetic should not be defined because it is unimplemented in libc++!"
7180-
# endif
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# ifndef __cpp_lib_saturation_arithmetic
7171+
# error "__cpp_lib_saturation_arithmetic should be defined in c++26"
7172+
# endif
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# if __cpp_lib_saturation_arithmetic != 202311L
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# error "__cpp_lib_saturation_arithmetic should have the value 202311L in c++26"
71817175
# endif
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# ifndef __cpp_lib_scoped_lock

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