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concepts.hpp
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concepts.hpp
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/// \file
// CPP, the Concepts PreProcessor library
//
// Copyright Eric Niebler 2018-present
// Copyright (c) 2018-present, Facebook, Inc.
// Copyright (c) 2020-present, Google LLC.
//
// Use, modification and distribution is subject to the
// Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// This source code is licensed under the MIT license found in the
// LICENSE file in the root directory of this source tree.
//
// Project home: https://github.com/ericniebler/range-v3
//
#ifndef CPP_CONCEPTS_HPP
#define CPP_CONCEPTS_HPP
// clang-format off
#include <initializer_list>
#include <utility>
#include <type_traits>
#include <concepts/swap.hpp>
#include <concepts/type_traits.hpp>
// Disable buggy clang compatibility warning about "requires" and "concept" being
// C++20 keywords.
// https://bugs.llvm.org/show_bug.cgi?id=43708
#if defined(__clang__) && __cplusplus <= 201703L
#define CPP_PP_IGNORE_CXX2A_COMPAT_BEGIN \
CPP_DIAGNOSTIC_PUSH \
CPP_DIAGNOSTIC_IGNORE_CPP2A_COMPAT
#define CPP_PP_IGNORE_CXX2A_COMPAT_END \
CPP_DIAGNOSTIC_POP
#else
#define CPP_PP_IGNORE_CXX2A_COMPAT_BEGIN
#define CPP_PP_IGNORE_CXX2A_COMPAT_END
#endif
#if defined(_MSC_VER) && !defined(__clang__)
#define CPP_WORKAROUND_MSVC_779763 // FATAL_UNREACHABLE calling constexpr function via template parameter
#define CPP_WORKAROUND_MSVC_784772 // Failure to invoke *explicit* bool conversion in a constant expression
#endif
#if !defined(CPP_CXX_CONCEPTS)
#ifdef CPP_DOXYGEN_INVOKED
#define CPP_CXX_CONCEPTS 201800L
#elif defined(__cpp_concepts) && __cpp_concepts > 0
// gcc-6 concepts are too buggy to use
#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ >= 7
#define CPP_CXX_CONCEPTS __cpp_concepts
#else
#define CPP_CXX_CONCEPTS 0L
#endif
#else
#define CPP_CXX_CONCEPTS 0L
#endif
#endif
#define CPP_PP_CAT_(X, ...) X ## __VA_ARGS__
#define CPP_PP_CAT(X, ...) CPP_PP_CAT_(X, __VA_ARGS__)
#define CPP_PP_EVAL_(X, ARGS) X ARGS
#define CPP_PP_EVAL(X, ...) CPP_PP_EVAL_(X, (__VA_ARGS__))
#define CPP_PP_EVAL2_(X, ARGS) X ARGS
#define CPP_PP_EVAL2(X, ...) CPP_PP_EVAL2_(X, (__VA_ARGS__))
#define CPP_PP_EXPAND(...) __VA_ARGS__
#define CPP_PP_EAT(...)
#define CPP_PP_FIRST(LIST) CPP_PP_FIRST_ LIST
#define CPP_PP_FIRST_(...) __VA_ARGS__ CPP_PP_EAT
#define CPP_PP_SECOND(LIST) CPP_PP_SECOND_ LIST
#define CPP_PP_SECOND_(...) CPP_PP_EXPAND
#define CPP_PP_CHECK(...) CPP_PP_EXPAND(CPP_PP_CHECK_N(__VA_ARGS__, 0,))
#define CPP_PP_CHECK_N(x, n, ...) n
#define CPP_PP_PROBE(x) x, 1,
#define CPP_PP_PROBE_N(x, n) x, n,
#define CPP_PP_IS_PAREN(x) CPP_PP_CHECK(CPP_PP_IS_PAREN_PROBE x)
#define CPP_PP_IS_PAREN_PROBE(...) CPP_PP_PROBE(~)
// CPP_CXX_VA_OPT
#ifndef CPP_CXX_VA_OPT
#if __cplusplus > 201703L
#define CPP_CXX_VA_OPT_(...) CPP_PP_CHECK(__VA_OPT__(,) 1)
#define CPP_CXX_VA_OPT CPP_CXX_VA_OPT_(~)
#else
#define CPP_CXX_VA_OPT 0
#endif
#endif // CPP_CXX_VA_OPT
// The final CPP_PP_EXPAND here is to avoid
// https://stackoverflow.com/questions/5134523/msvc-doesnt-expand-va-args-correctly
#define CPP_PP_COUNT(...) \
CPP_PP_EXPAND(CPP_PP_COUNT_(__VA_ARGS__, \
50, 49, 48, 47, 46, 45, 44, 43, 42, 41, \
40, 39, 38, 37, 36, 35, 34, 33, 32, 31, \
30, 29, 28, 27, 26, 25, 24, 23, 22, 21, \
20, 19, 18, 17, 16, 15, 14, 13, 12, 11, \
10, 9, 8, 7, 6, 5, 4, 3, 2, 1,))
#define CPP_PP_COUNT_( \
_01, _02, _03, _04, _05, _06, _07, _08, _09, _10, \
_11, _12, _13, _14, _15, _16, _17, _18, _19, _20, \
_21, _22, _23, _24, _25, _26, _27, _28, _29, _30, \
_31, _32, _33, _34, _35, _36, _37, _38, _39, _40, \
_41, _42, _43, _44, _45, _46, _47, _48, _49, _50, N, ...) \
N
#define CPP_PP_IIF(BIT) CPP_PP_CAT_(CPP_PP_IIF_, BIT)
#define CPP_PP_IIF_0(TRUE, ...) __VA_ARGS__
#define CPP_PP_IIF_1(TRUE, ...) TRUE
#define CPP_PP_LPAREN (
#define CPP_PP_RPAREN )
#define CPP_PP_NOT(BIT) CPP_PP_CAT_(CPP_PP_NOT_, BIT)
#define CPP_PP_NOT_0 1
#define CPP_PP_NOT_1 0
#define CPP_PP_EMPTY()
#define CPP_PP_COMMA() ,
#define CPP_PP_LBRACE() {
#define CPP_PP_RBRACE() }
#define CPP_PP_COMMA_IIF(X) \
CPP_PP_IIF(X)(CPP_PP_EMPTY, CPP_PP_COMMA)()
#define CPP_PP_FOR_EACH(M, ...) \
CPP_PP_FOR_EACH_N(CPP_PP_COUNT(__VA_ARGS__), M, __VA_ARGS__)
#define CPP_PP_FOR_EACH_N(N, M, ...) \
CPP_PP_CAT(CPP_PP_FOR_EACH_, N)(M, __VA_ARGS__)
#define CPP_PP_FOR_EACH_1(M, _1) \
M(_1)
#define CPP_PP_FOR_EACH_2(M, _1, _2) \
M(_1), M(_2)
#define CPP_PP_FOR_EACH_3(M, _1, _2, _3) \
M(_1), M(_2), M(_3)
#define CPP_PP_FOR_EACH_4(M, _1, _2, _3, _4) \
M(_1), M(_2), M(_3), M(_4)
#define CPP_PP_FOR_EACH_5(M, _1, _2, _3, _4, _5) \
M(_1), M(_2), M(_3), M(_4), M(_5)
#define CPP_PP_FOR_EACH_6(M, _1, _2, _3, _4, _5, _6) \
M(_1), M(_2), M(_3), M(_4), M(_5), M(_6)
#define CPP_PP_FOR_EACH_7(M, _1, _2, _3, _4, _5, _6, _7) \
M(_1), M(_2), M(_3), M(_4), M(_5), M(_6), M(_7)
#define CPP_PP_FOR_EACH_8(M, _1, _2, _3, _4, _5, _6, _7, _8) \
M(_1), M(_2), M(_3), M(_4), M(_5), M(_6), M(_7), M(_8)
#define CPP_PP_PROBE_EMPTY_PROBE_CPP_PP_PROBE_EMPTY \
CPP_PP_PROBE(~)
#define CPP_PP_PROBE_EMPTY()
#define CPP_PP_IS_NOT_EMPTY(...) \
CPP_PP_EVAL( \
CPP_PP_CHECK, \
CPP_PP_CAT( \
CPP_PP_PROBE_EMPTY_PROBE_, \
CPP_PP_PROBE_EMPTY __VA_ARGS__ ()))
#if defined(_MSC_VER) && !defined(__clang__) && (__cplusplus <= 201703L)
#define CPP_BOOL(...) ::meta::bool_<__VA_ARGS__>::value
#define CPP_TRUE_FN \
!::concepts::detail::instance_< \
decltype(CPP_true_fn(::concepts::detail::xNil{}))>
#define CPP_NOT(...) (!CPP_BOOL(__VA_ARGS__))
#else
#define CPP_BOOL(...) __VA_ARGS__
#define CPP_TRUE_FN CPP_true_fn(::concepts::detail::xNil{})
#define CPP_NOT(...) (!(__VA_ARGS__))
#endif
#define CPP_assert(...) \
static_assert(static_cast<bool>(__VA_ARGS__), \
"Concept assertion failed : " #__VA_ARGS__)
#define CPP_assert_msg static_assert
#if CPP_CXX_CONCEPTS || defined(CPP_DOXYGEN_INVOKED)
#define CPP_concept META_CONCEPT
#define CPP_and &&
#else
#define CPP_concept CPP_INLINE_VAR constexpr bool
#define CPP_and CPP_and_sfinae
#endif
////////////////////////////////////////////////////////////////////////////////
// CPP_template
// Usage:
// CPP_template(typename A, typename B)
// (requires Concept1<A> CPP_and Concept2<B>)
// void foo(A a, B b)
// {}
#if CPP_CXX_CONCEPTS
#if defined(CPP_DOXYGEN_INVOKED)
#define CPP_template(...) template<__VA_ARGS__> CPP_TEMPLATE_EXPAND_
#define CPP_TEMPLATE_EXPAND_(X,Y) X Y
#else
#define CPP_template(...) template<__VA_ARGS__ CPP_TEMPLATE_AUX_
#endif
#define CPP_template_def CPP_template
#define CPP_member
#define CPP_ctor(TYPE) TYPE CPP_CTOR_IMPL_1_
#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 10
#define CPP_auto_member template<typename...>
#else
#define CPP_auto_member
#endif
/// INTERNAL ONLY
#define CPP_CTOR_IMPL_1_(...) (__VA_ARGS__) CPP_PP_EXPAND
/// INTERNAL ONLY
#define CPP_TEMPLATE_AUX_(...) \
> CPP_PP_CAT( \
CPP_TEMPLATE_AUX_, \
CPP_TEMPLATE_AUX_WHICH_(__VA_ARGS__,))(__VA_ARGS__)
/// INTERNAL ONLY
#define CPP_TEMPLATE_AUX_WHICH_(FIRST, ...) \
CPP_PP_EVAL( \
CPP_PP_CHECK, \
CPP_PP_CAT(CPP_TEMPLATE_PROBE_CONCEPT_, FIRST))
/// INTERNAL ONLY
#define CPP_TEMPLATE_PROBE_CONCEPT_concept \
CPP_PP_PROBE(~)
// A template with a requires clause
/// INTERNAL ONLY
#define CPP_TEMPLATE_AUX_0(...) __VA_ARGS__
// A concept definition
/// INTERNAL ONLY
#define CPP_TEMPLATE_AUX_1(DECL, ...) \
CPP_concept CPP_CONCEPT_NAME_(DECL) = __VA_ARGS__
#if defined(CPP_DOXYGEN_INVOKED)
#define CPP_concept_ref(NAME, ...) \
NAME<__VA_ARGS__>
#else
#define CPP_concept_ref(NAME, ...) \
CPP_PP_CAT(NAME, concept_)<__VA_ARGS__>
#endif
#else // ^^^^ with concepts / without concepts vvvv
#define CPP_template CPP_template_sfinae
#define CPP_template_def CPP_template_def_sfinae
#define CPP_member CPP_member_sfinae
#define CPP_auto_member CPP_member_sfinae
#define CPP_ctor CPP_ctor_sfinae
#define CPP_concept_ref(NAME, ...) \
(1u == sizeof(CPP_PP_CAT(NAME, concept_)( \
(::concepts::detail::tag<__VA_ARGS__>*)nullptr)))
/// INTERNAL ONLY
#define CPP_TEMPLATE_AUX_ CPP_TEMPLATE_SFINAE_AUX_
#endif
#define CPP_template_sfinae(...) \
CPP_PP_IGNORE_CXX2A_COMPAT_BEGIN \
template<__VA_ARGS__ CPP_TEMPLATE_SFINAE_AUX_
/// INTERNAL ONLY
#define CPP_TEMPLATE_SFINAE_PROBE_CONCEPT_concept \
CPP_PP_PROBE(~)
/// INTERNAL ONLY
#define CPP_TEMPLATE_SFINAE_AUX_WHICH_(FIRST, ...) \
CPP_PP_EVAL( \
CPP_PP_CHECK, \
CPP_PP_CAT(CPP_TEMPLATE_SFINAE_PROBE_CONCEPT_, FIRST))
/// INTERNAL ONLY
#define CPP_TEMPLATE_SFINAE_AUX_(...) \
CPP_PP_CAT( \
CPP_TEMPLATE_SFINAE_AUX_, \
CPP_TEMPLATE_SFINAE_AUX_WHICH_(__VA_ARGS__,))(__VA_ARGS__)
// A template with a requires clause
/// INTERNAL ONLY
#define CPP_TEMPLATE_SFINAE_AUX_0(...) , \
bool CPP_true = true, \
std::enable_if_t< \
CPP_PP_CAT(CPP_TEMPLATE_SFINAE_AUX_3_, __VA_ARGS__) && \
CPP_BOOL(CPP_true), \
int> = 0> \
CPP_PP_IGNORE_CXX2A_COMPAT_END
// A concept definition
/// INTERNAL ONLY
#define CPP_TEMPLATE_SFINAE_AUX_1(DECL, ...) , \
bool CPP_true = true, \
std::enable_if_t<__VA_ARGS__ && CPP_BOOL(CPP_true), int> = 0> \
auto CPP_CONCEPT_NAME_(DECL)( \
::concepts::detail::tag<CPP_CONCEPT_PARAMS_(DECL)>*) \
-> char(&)[1]; \
auto CPP_CONCEPT_NAME_(DECL)(...) -> char(&)[2] \
CPP_PP_IGNORE_CXX2A_COMPAT_END
/// INTERNAL ONLY
#define CPP_CONCEPT_NAME_(DECL) \
CPP_PP_EVAL( \
CPP_PP_CAT, \
CPP_PP_EVAL(CPP_PP_FIRST, CPP_EAT_CONCEPT_(DECL)), concept_)
/// INTERNAL ONLY
#define CPP_CONCEPT_PARAMS_(DECL) \
CPP_PP_EVAL(CPP_PP_SECOND, CPP_EAT_CONCEPT_(DECL))
/// INTERNAL ONLY
#define CPP_EAT_CONCEPT_(DECL) \
CPP_PP_CAT(CPP_EAT_CONCEPT_, DECL)
/// INTERNAL ONLY
#define CPP_EAT_CONCEPT_concept
/// INTERNAL ONLY
#define CPP_and_sfinae \
&& CPP_BOOL(CPP_true), int> = 0, std::enable_if_t<
/// INTERNAL ONLY
#define CPP_template_def_sfinae(...) \
template<__VA_ARGS__ CPP_TEMPLATE_DEF_SFINAE_AUX_
/// INTERNAL ONLY
#define CPP_TEMPLATE_DEF_SFINAE_AUX_(...) , \
bool CPP_true, \
std::enable_if_t< \
CPP_PP_CAT(CPP_TEMPLATE_SFINAE_AUX_3_, __VA_ARGS__) && \
CPP_BOOL(CPP_true), \
int>>
/// INTERNAL ONLY
#define CPP_and_sfinae_def \
&& CPP_BOOL(CPP_true), int>, std::enable_if_t<
/// INTERNAL ONLY
#define CPP_TEMPLATE_SFINAE_AUX_3_requires
/// INTERNAL ONLY
#define CPP_member_sfinae \
CPP_broken_friend_member
/// INTERNAL ONLY
#define CPP_ctor_sfinae(TYPE) \
CPP_PP_IGNORE_CXX2A_COMPAT_BEGIN \
TYPE CPP_CTOR_SFINAE_IMPL_1_
/// INTERNAL ONLY
#define CPP_CTOR_SFINAE_IMPL_1_(...) \
(__VA_ARGS__ \
CPP_PP_COMMA_IIF( \
CPP_PP_NOT(CPP_PP_IS_NOT_EMPTY(__VA_ARGS__))) \
CPP_CTOR_SFINAE_REQUIRES
/// INTERNAL ONLY
#define CPP_CTOR_SFINAE_PROBE_NOEXCEPT_noexcept \
CPP_PP_PROBE(~)
/// INTERNAL ONLY
#define CPP_CTOR_SFINAE_MAKE_PROBE(FIRST,...) \
CPP_PP_CAT(CPP_CTOR_SFINAE_PROBE_NOEXCEPT_, FIRST)
/// INTERNAL ONLY
#define CPP_CTOR_SFINAE_REQUIRES(...) \
CPP_PP_CAT( \
CPP_CTOR_SFINAE_REQUIRES_, \
CPP_PP_EVAL( \
CPP_PP_CHECK, \
CPP_CTOR_SFINAE_MAKE_PROBE(__VA_ARGS__,)))(__VA_ARGS__)
// No noexcept-clause:
/// INTERNAL ONLY
#define CPP_CTOR_SFINAE_REQUIRES_0(...) \
std::enable_if_t< \
CPP_PP_CAT(CPP_TEMPLATE_SFINAE_AUX_3_, __VA_ARGS__) && CPP_TRUE_FN, \
::concepts::detail::KnightsWhoSayNil \
> = {}) \
CPP_PP_IGNORE_CXX2A_COMPAT_END
// Yes noexcept-clause:
/// INTERNAL ONLY
#define CPP_CTOR_SFINAE_REQUIRES_1(...) \
std::enable_if_t< \
CPP_PP_EVAL(CPP_PP_CAT, \
CPP_TEMPLATE_SFINAE_AUX_3_, \
CPP_PP_CAT(CPP_CTOR_SFINAE_EAT_NOEXCEPT_, __VA_ARGS__)) && CPP_TRUE_FN,\
::concepts::detail::KnightsWhoSayNil \
> = {}) \
CPP_PP_EXPAND(CPP_PP_CAT(CPP_CTOR_SFINAE_SHOW_NOEXCEPT_, __VA_ARGS__)))
/// INTERNAL ONLY
#define CPP_CTOR_SFINAE_EAT_NOEXCEPT_noexcept(...)
/// INTERNAL ONLY
#define CPP_CTOR_SFINAE_SHOW_NOEXCEPT_noexcept(...) \
noexcept(__VA_ARGS__) \
CPP_PP_IGNORE_CXX2A_COMPAT_END \
CPP_PP_EAT CPP_PP_LPAREN
#ifdef CPP_DOXYGEN_INVOKED
/// INTERNAL ONLY
#define CPP_broken_friend_ret(...) \
__VA_ARGS__ CPP_PP_EXPAND
#else // ^^^ CPP_DOXYGEN_INVOKED / not CPP_DOXYGEN_INVOKED vvv
#define CPP_broken_friend_ret(...) \
::concepts::return_t< \
__VA_ARGS__, \
std::enable_if_t<CPP_BROKEN_FRIEND_RETURN_TYPE_AUX_
/// INTERNAL ONLY
#define CPP_BROKEN_FRIEND_RETURN_TYPE_AUX_(...) \
CPP_BROKEN_FRIEND_RETURN_TYPE_AUX_3_(CPP_PP_CAT( \
CPP_TEMPLATE_AUX_2_, __VA_ARGS__))
/// INTERNAL ONLY
#define CPP_TEMPLATE_AUX_2_requires
/// INTERNAL ONLY
#define CPP_BROKEN_FRIEND_RETURN_TYPE_AUX_3_(...) \
(__VA_ARGS__ && CPP_TRUE_FN)>>
#ifdef CPP_WORKAROUND_MSVC_779763
/// INTERNAL ONLY
#define CPP_broken_friend_member \
template<::concepts::detail::CPP_true_t const &CPP_true_fn = \
::concepts::detail::CPP_true_fn_>
#else // ^^^ workaround / no workaround vvv
/// INTERNAL ONLY
#define CPP_broken_friend_member \
template<bool (&CPP_true_fn)(::concepts::detail::xNil) = \
::concepts::detail::CPP_true_fn>
#endif // CPP_WORKAROUND_MSVC_779763
#endif
#if CPP_CXX_CONCEPTS
#if defined(CPP_DOXYGEN_INVOKED)
#define CPP_requires(NAME, REQS) \
concept NAME = \
CPP_PP_CAT(CPP_REQUIRES_, REQS)
#define CPP_requires_ref(NAME, ...) \
NAME<__VA_ARGS__>
#else
#define CPP_requires(NAME, REQS) \
CPP_concept CPP_PP_CAT(NAME, requires_) = \
CPP_PP_CAT(CPP_REQUIRES_, REQS)
#define CPP_requires_ref(NAME, ...) \
CPP_PP_CAT(NAME, requires_)<__VA_ARGS__>
#endif
/// INTERNAL ONLY
#define CPP_REQUIRES_requires(...) \
requires(__VA_ARGS__) CPP_REQUIRES_AUX_
/// INTERNAL ONLY
#define CPP_REQUIRES_AUX_(...) \
{ __VA_ARGS__; }
#else
#define CPP_requires(NAME, REQS) \
auto CPP_PP_CAT(NAME, requires_test_) \
CPP_REQUIRES_AUX_(NAME, CPP_REQUIRES_ ## REQS)
#define CPP_requires_ref(NAME, ...) \
(1u == sizeof(CPP_PP_CAT(NAME, requires_)( \
(::concepts::detail::tag<__VA_ARGS__>*)nullptr)))
/// INTERNAL ONLY
#define CPP_REQUIRES_requires(...) \
(__VA_ARGS__) -> decltype CPP_REQUIRES_RETURN_
/// INTERNAL ONLY
#define CPP_REQUIRES_RETURN_(...) (__VA_ARGS__, void()) {}
/// INTERNAL ONLY
#define CPP_REQUIRES_AUX_(NAME, ...) \
__VA_ARGS__ \
template<typename... As> \
auto CPP_PP_CAT(NAME, requires_)( \
::concepts::detail::tag<As...> *, \
decltype(&CPP_PP_CAT(NAME, requires_test_)<As...>) = nullptr) \
-> char(&)[1]; \
auto CPP_PP_CAT(NAME, requires_)(...) -> char(&)[2]
#endif
#if CPP_CXX_CONCEPTS
#define CPP_ret(...) \
__VA_ARGS__ CPP_PP_EXPAND
#else
#define CPP_ret \
CPP_broken_friend_ret
#endif
////////////////////////////////////////////////////////////////////////////////
// CPP_fun
#if CPP_CXX_CONCEPTS
/// INTERNAL ONLY
#define CPP_FUN_IMPL_1_(...) \
(__VA_ARGS__) \
CPP_PP_EXPAND
#define CPP_fun(X) X CPP_FUN_IMPL_1_
#else
/// INTERNAL ONLY
#define CPP_FUN_IMPL_1_(...) \
(__VA_ARGS__ \
CPP_PP_COMMA_IIF( \
CPP_PP_NOT(CPP_PP_IS_NOT_EMPTY(__VA_ARGS__))) \
CPP_FUN_IMPL_REQUIRES
/// INTERNAL ONLY
#define CPP_FUN_IMPL_REQUIRES(...) \
CPP_PP_EVAL2_( \
CPP_FUN_IMPL_SELECT_CONST_, \
(__VA_ARGS__,) \
)(__VA_ARGS__)
/// INTERNAL ONLY
#define CPP_FUN_IMPL_SELECT_CONST_(MAYBE_CONST, ...) \
CPP_PP_CAT(CPP_FUN_IMPL_SELECT_CONST_, \
CPP_PP_EVAL(CPP_PP_CHECK, CPP_PP_CAT( \
CPP_PP_PROBE_CONST_PROBE_, MAYBE_CONST)))
/// INTERNAL ONLY
#define CPP_PP_PROBE_CONST_PROBE_const CPP_PP_PROBE(~)
/// INTERNAL ONLY
#define CPP_FUN_IMPL_SELECT_CONST_1(...) \
CPP_PP_EVAL( \
CPP_FUN_IMPL_SELECT_CONST_NOEXCEPT_, \
CPP_PP_CAT(CPP_FUN_IMPL_EAT_CONST_, __VA_ARGS__),)( \
CPP_PP_CAT(CPP_FUN_IMPL_EAT_CONST_, __VA_ARGS__))
/// INTERNAL ONLY
#define CPP_FUN_IMPL_SELECT_CONST_NOEXCEPT_(MAYBE_NOEXCEPT, ...) \
CPP_PP_CAT(CPP_FUN_IMPL_SELECT_CONST_NOEXCEPT_, \
CPP_PP_EVAL2(CPP_PP_CHECK, CPP_PP_CAT( \
CPP_PP_PROBE_NOEXCEPT_PROBE_, MAYBE_NOEXCEPT)))
/// INTERNAL ONLY
#define CPP_PP_PROBE_NOEXCEPT_PROBE_noexcept CPP_PP_PROBE(~)
/// INTERNAL ONLY
#define CPP_FUN_IMPL_SELECT_CONST_NOEXCEPT_0(...) \
std::enable_if_t< \
CPP_PP_EVAL( \
CPP_PP_CAT, \
CPP_FUN_IMPL_EAT_REQUIRES_, \
__VA_ARGS__) && CPP_TRUE_FN, \
::concepts::detail::KnightsWhoSayNil \
> = {}) const \
CPP_PP_IGNORE_CXX2A_COMPAT_END
/// INTERNAL ONLY
#define CPP_FUN_IMPL_SELECT_CONST_NOEXCEPT_1(...) \
std::enable_if_t< \
CPP_PP_EVAL( \
CPP_PP_CAT, \
CPP_FUN_IMPL_EAT_REQUIRES_, \
CPP_PP_CAT(CPP_FUN_IMPL_EAT_NOEXCEPT_, __VA_ARGS__)) && CPP_TRUE_FN,\
::concepts::detail::KnightsWhoSayNil \
> = {}) const \
CPP_PP_EXPAND(CPP_PP_CAT(CPP_FUN_IMPL_SHOW_NOEXCEPT_, __VA_ARGS__)))
/// INTERNAL ONLY
#define CPP_FUN_IMPL_EAT_NOEXCEPT_noexcept(...)
/// INTERNAL ONLY
#define CPP_FUN_IMPL_SHOW_NOEXCEPT_noexcept(...) \
noexcept(__VA_ARGS__) CPP_PP_IGNORE_CXX2A_COMPAT_END \
CPP_PP_EAT CPP_PP_LPAREN
/// INTERNAL ONLY
#define CPP_FUN_IMPL_SELECT_CONST_0(...) \
CPP_PP_EVAL_( \
CPP_FUN_IMPL_SELECT_NONCONST_NOEXCEPT_, \
(__VA_ARGS__,) \
)(__VA_ARGS__)
/// INTERNAL ONLY
#define CPP_FUN_IMPL_SELECT_NONCONST_NOEXCEPT_(MAYBE_NOEXCEPT, ...) \
CPP_PP_CAT(CPP_FUN_IMPL_SELECT_NONCONST_NOEXCEPT_, \
CPP_PP_EVAL2(CPP_PP_CHECK, CPP_PP_CAT( \
CPP_PP_PROBE_NOEXCEPT_PROBE_, MAYBE_NOEXCEPT)))
/// INTERNAL ONLY
#define CPP_FUN_IMPL_SELECT_NONCONST_NOEXCEPT_0(...) \
std::enable_if_t< \
CPP_PP_CAT(CPP_FUN_IMPL_EAT_REQUIRES_, __VA_ARGS__) && CPP_TRUE_FN, \
::concepts::detail::KnightsWhoSayNil \
> = {}) \
CPP_PP_IGNORE_CXX2A_COMPAT_END
/// INTERNAL ONLY
#define CPP_FUN_IMPL_SELECT_NONCONST_NOEXCEPT_1(...) \
std::enable_if_t< \
CPP_PP_EVAL( \
CPP_PP_CAT, \
CPP_FUN_IMPL_EAT_REQUIRES_, \
CPP_PP_CAT(CPP_FUN_IMPL_EAT_NOEXCEPT_, __VA_ARGS__) \
) && CPP_TRUE_FN, \
::concepts::detail::KnightsWhoSayNil \
> = {}) \
CPP_PP_EXPAND(CPP_PP_CAT(CPP_FUN_IMPL_SHOW_NOEXCEPT_, __VA_ARGS__)))
/// INTERNAL ONLY
#define CPP_FUN_IMPL_EAT_CONST_const
/// INTERNAL ONLY
#define CPP_FUN_IMPL_EAT_REQUIRES_requires
////////////////////////////////////////////////////////////////////////////////
// CPP_fun
// Usage:
// template <typename A, typename B>
// void CPP_fun(foo)(A a, B b)([const]opt [noexcept(true)]opt
// requires Concept1<A> && Concept2<B>)
// {}
//
// Note: This macro cannot be used when the last function argument is a
// parameter pack.
#define CPP_fun(X) CPP_PP_IGNORE_CXX2A_COMPAT_BEGIN X CPP_FUN_IMPL_1_
#endif
////////////////////////////////////////////////////////////////////////////////
// CPP_auto_fun
// Usage:
// template <typename A, typename B>
// auto CPP_auto_fun(foo)(A a, B b)([const]opt [noexcept(cond)]opt)opt
// (
// return a + b
// )
#define CPP_auto_fun(X) X CPP_AUTO_FUN_IMPL_
/// INTERNAL ONLY
#define CPP_AUTO_FUN_IMPL_(...) (__VA_ARGS__) CPP_AUTO_FUN_RETURNS_
/// INTERNAL ONLY
#define CPP_AUTO_FUN_RETURNS_(...) \
CPP_PP_EVAL2_( \
CPP_AUTO_FUN_SELECT_RETURNS_, \
(__VA_ARGS__,) \
)(__VA_ARGS__)
/// INTERNAL ONLY
#define CPP_AUTO_FUN_SELECT_RETURNS_(MAYBE_CONST, ...) \
CPP_PP_CAT(CPP_AUTO_FUN_RETURNS_CONST_, \
CPP_PP_EVAL(CPP_PP_CHECK, CPP_PP_CAT( \
CPP_PP_PROBE_CONST_MUTABLE_PROBE_, MAYBE_CONST)))
/// INTERNAL ONLY
#define CPP_PP_PROBE_CONST_MUTABLE_PROBE_const CPP_PP_PROBE_N(~, 1)
/// INTERNAL ONLY
#define CPP_PP_PROBE_CONST_MUTABLE_PROBE_mutable CPP_PP_PROBE_N(~, 2)
/// INTERNAL ONLY
#define CPP_PP_EAT_MUTABLE_mutable
/// INTERNAL ONLY
#define CPP_AUTO_FUN_RETURNS_CONST_2(...) \
CPP_PP_CAT(CPP_PP_EAT_MUTABLE_, __VA_ARGS__) CPP_AUTO_FUN_RETURNS_CONST_0
/// INTERNAL ONLY
#define CPP_AUTO_FUN_RETURNS_CONST_1(...) \
__VA_ARGS__ CPP_AUTO_FUN_RETURNS_CONST_0
/// INTERNAL ONLY
#define CPP_AUTO_FUN_RETURNS_CONST_0(...) \
CPP_PP_EVAL(CPP_AUTO_FUN_DECLTYPE_NOEXCEPT_, \
CPP_PP_CAT(CPP_AUTO_FUN_RETURNS_, __VA_ARGS__))
/// INTERNAL ONLY
#define CPP_AUTO_FUN_RETURNS_return
#ifdef __cpp_guaranteed_copy_elision
/// INTERNAL ONLY
#define CPP_AUTO_FUN_DECLTYPE_NOEXCEPT_(...) \
noexcept(noexcept(__VA_ARGS__)) -> decltype(__VA_ARGS__) \
{ return (__VA_ARGS__); }
#else
/// INTERNAL ONLY
#define CPP_AUTO_FUN_DECLTYPE_NOEXCEPT_(...) \
noexcept(noexcept(decltype(__VA_ARGS__)(__VA_ARGS__))) -> \
decltype(__VA_ARGS__) \
{ return (__VA_ARGS__); }
#endif
#if defined(CPP_DOXYGEN_INVOKED)
#define concept(NAME) concept NAME CPP_CONCEPT_EQUALS_
#define CPP_CONCEPT_EQUALS_(...) =
#endif
namespace concepts
{
template<bool B>
using bool_ = std::integral_constant<bool, B>;
#if defined(__cpp_fold_expressions) && __cpp_fold_expressions >= 201603
template<bool...Bs>
CPP_INLINE_VAR constexpr bool and_v = (Bs &&...);
template<bool...Bs>
CPP_INLINE_VAR constexpr bool or_v = (Bs ||...);
#else
namespace detail
{
template<bool...>
struct bools;
} // namespace detail
template<bool...Bs>
CPP_INLINE_VAR constexpr bool and_v =
META_IS_SAME(detail::bools<Bs..., true>, detail::bools<true, Bs...>);
template<bool...Bs>
CPP_INLINE_VAR constexpr bool or_v =
!META_IS_SAME(detail::bools<Bs..., false>, detail::bools<false, Bs...>);
#endif
template<typename>
struct return_t_
{
template<typename T>
using invoke = T;
};
template<typename T, typename EnableIf>
using return_t = meta::invoke<return_t_<EnableIf>, T>;
/// \cond
namespace detail
{
struct ignore
{
template<class... Args>
constexpr ignore(Args&&...) noexcept {}
};
template<class>
constexpr bool true_()
{
return true;
}
template<typename...>
struct tag;
template<typename T>
CPP_INLINE_VAR constexpr T instance_ = T{};
template<typename>
constexpr bool requires_()
{
return true;
}
struct KnightsWhoSayNil
{};
#ifdef CPP_WORKAROUND_MSVC_779763
enum class xNil {};
struct CPP_true_t
{
constexpr bool operator()(KnightsWhoSayNil) const noexcept
{
return true;
}
constexpr bool operator()(xNil) const noexcept
{
return true;
}
};
CPP_INLINE_VAR constexpr CPP_true_t CPP_true_fn_ {};
constexpr bool CPP_true_fn(xNil)
{
return true;
}
#else
using xNil = KnightsWhoSayNil;
#endif
constexpr bool CPP_true_fn(KnightsWhoSayNil)
{
return true;
}
} // namespace detail
/// \endcond
#if defined(__clang__) || defined(_MSC_VER) || defined(__NVCOMPILER)
template<bool B>
std::enable_if_t<B> requires_()
{}
#else
template<bool B>
CPP_INLINE_VAR constexpr std::enable_if_t<B, int> requires_ = 0;
#endif
inline namespace defs
{
////////////////////////////////////////////////////////////////////////
// Utility concepts
////////////////////////////////////////////////////////////////////////
/// \concept is_true
/// \brief The \c is_true concept
template<bool B>
CPP_concept is_true = B;
/// \concept type
/// \brief The \c type concept
template<typename... Args>
CPP_concept type = true;
/// \concept satisfies
/// \brief The \c satisfies concept
template<class T, template<typename...> class Trait, typename... Args>
CPP_concept satisfies =
static_cast<bool>(Trait<T, Args...>::type::value);
////////////////////////////////////////////////////////////////////////
// Core language concepts
////////////////////////////////////////////////////////////////////////
/// \concept same_as
/// \brief The \c same_as concept
template<typename A, typename B>
CPP_concept same_as =
META_IS_SAME(A, B) && META_IS_SAME(B, A);
/// \cond
/// \concept not_same_as_
/// \brief The \c not_same_as_ concept
template<typename A, typename B>
CPP_concept not_same_as_ =
(!same_as<remove_cvref_t<A>, remove_cvref_t<B>>);
/// \endcond
// Workaround bug in the Standard Library:
// From cannot be an incomplete class type despite that
// is_convertible<X, Y> should be equivalent to is_convertible<X&&, Y>
// in such a case.
/// \concept implicitly_convertible_to
/// \brief The \c implicitly_convertible_to concept
template<typename From, typename To>
CPP_concept implicitly_convertible_to =
std::is_convertible<std::add_rvalue_reference_t<From>, To>::value;
/// \concept explicitly_convertible_to_
/// \brief The \c explicitly_convertible_to_ concept
template<typename From, typename To>
CPP_requires(explicitly_convertible_to_,
requires(From(*from)()) //
(
static_cast<To>(from())
));
/// \concept explicitly_convertible_to
/// \brief The \c explicitly_convertible_to concept
template<typename From, typename To>
CPP_concept explicitly_convertible_to =
CPP_requires_ref(concepts::explicitly_convertible_to_, From, To);
/// \concept convertible_to
/// \brief The \c convertible_to concept
template<typename From, typename To>
CPP_concept convertible_to =
implicitly_convertible_to<From, To> &&
explicitly_convertible_to<From, To>;
/// \concept derived_from_
/// \brief The \c derived_from_ concept
CPP_template(typename T, typename U)(
concept (derived_from_)(T, U),
convertible_to<T const volatile *, U const volatile *>
);
/// \concept derived_from
/// \brief The \c derived_from concept
template<typename T, typename U>
CPP_concept derived_from =
META_IS_BASE_OF(U, T) &&
CPP_concept_ref(concepts::derived_from_, T, U);
/// \concept common_reference_with_
/// \brief The \c common_reference_with_ concept
CPP_template(typename T, typename U)(
concept (common_reference_with_)(T, U),
same_as<common_reference_t<T, U>, common_reference_t<U, T>> CPP_and
convertible_to<T, common_reference_t<T, U>> CPP_and
convertible_to<U, common_reference_t<T, U>>
);
/// \concept common_reference_with
/// \brief The \c common_reference_with concept
template<typename T, typename U>
CPP_concept common_reference_with =
CPP_concept_ref(concepts::common_reference_with_, T, U);
/// \concept common_with_
/// \brief The \c common_with_ concept
CPP_template(typename T, typename U)(
concept (common_with_)(T, U),
same_as<common_type_t<T, U>, common_type_t<U, T>> CPP_and
convertible_to<T, common_type_t<T, U>> CPP_and
convertible_to<U, common_type_t<T, U>> CPP_and
common_reference_with<
std::add_lvalue_reference_t<T const>,
std::add_lvalue_reference_t<U const>> CPP_and
common_reference_with<
std::add_lvalue_reference_t<common_type_t<T, U>>,
common_reference_t<
std::add_lvalue_reference_t<T const>,
std::add_lvalue_reference_t<U const>>>
);
/// \concept common_with
/// \brief The \c common_with concept
template<typename T, typename U>
CPP_concept common_with =
CPP_concept_ref(concepts::common_with_, T, U);
/// \concept integral
/// \brief The \c integral concept
template<typename T>
CPP_concept integral =
std::is_integral<T>::value;
/// \concept signed_integral
/// \brief The \c signed_integral concept
template<typename T>
CPP_concept signed_integral =
integral<T> &&
std::is_signed<T>::value;
/// \concept unsigned_integral
/// \brief The \c unsigned_integral concept
template<typename T>
CPP_concept unsigned_integral =
integral<T> &&
!signed_integral<T>;
/// \concept assignable_from_
/// \brief The \c assignable_from_ concept
template<typename T, typename U>
CPP_requires(assignable_from_,
requires(T t, U && u) //
(
t = (U &&) u,
requires_<same_as<T, decltype(t = (U &&) u)>>
));
/// \concept assignable_from
/// \brief The \c assignable_from concept
template<typename T, typename U>
CPP_concept assignable_from =
std::is_lvalue_reference<T>::value &&
common_reference_with<detail::as_cref_t<T>, detail::as_cref_t<U>> &&
CPP_requires_ref(defs::assignable_from_, T, U);
/// \concept swappable_
/// \brief The \c swappable_ concept
template<typename T>
CPP_requires(swappable_,
requires(T & t, T & u) //
(
concepts::swap(t, u)
));
/// \concept swappable
/// \brief The \c swappable concept
template<typename T>
CPP_concept swappable =
CPP_requires_ref(defs::swappable_, T);
/// \concept swappable_with_
/// \brief The \c swappable_with_ concept
template<typename T, typename U>
CPP_requires(swappable_with_,
requires(T && t, U && u) //
(