xref: /freebsd-10.2-release/contrib/libc++/include/type_traits

// -*- C++ -*-
//===------------------------ type_traits ---------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_TYPE_TRAITS
#define _LIBCPP_TYPE_TRAITS

/*
    type_traits synopsis

namespace std
{

    // helper class:
    template <class T, T v> struct integral_constant;
    typedef integral_constant<bool, true>  true_type;
    typedef integral_constant<bool, false> false_type;

    // helper traits
    template <bool, class T = void> struct enable_if;
    template <bool, class T, class F> struct conditional;

    // Primary classification traits:
    template <class T> struct is_void;
    template <class T> struct is_integral;
    template <class T> struct is_floating_point;
    template <class T> struct is_array;
    template <class T> struct is_pointer;
    template <class T> struct is_lvalue_reference;
    template <class T> struct is_rvalue_reference;
    template <class T> struct is_member_object_pointer;
    template <class T> struct is_member_function_pointer;
    template <class T> struct is_enum;
    template <class T> struct is_union;
    template <class T> struct is_class;
    template <class T> struct is_function;

    // Secondary classification traits:
    template <class T> struct is_reference;
    template <class T> struct is_arithmetic;
    template <class T> struct is_fundamental;
    template <class T> struct is_member_pointer;
    template <class T> struct is_scalar;
    template <class T> struct is_object;
    template <class T> struct is_compound;

    // Const-volatile properties and transformations:
    template <class T> struct is_const;
    template <class T> struct is_volatile;
    template <class T> struct remove_const;
    template <class T> struct remove_volatile;
    template <class T> struct remove_cv;
    template <class T> struct add_const;
    template <class T> struct add_volatile;
    template <class T> struct add_cv;

    // Reference transformations:
    template <class T> struct remove_reference;
    template <class T> struct add_lvalue_reference;
    template <class T> struct add_rvalue_reference;

    // Pointer transformations:
    template <class T> struct remove_pointer;
    template <class T> struct add_pointer;

    // Integral properties:
    template <class T> struct is_signed;
    template <class T> struct is_unsigned;
    template <class T> struct make_signed;
    template <class T> struct make_unsigned;

    // Array properties and transformations:
    template <class T> struct rank;
    template <class T, unsigned I = 0> struct extent;
    template <class T> struct remove_extent;
    template <class T> struct remove_all_extents;

    // Member introspection:
    template <class T> struct is_pod;
    template <class T> struct is_trivial;
    template <class T> struct is_trivially_copyable;
    template <class T> struct is_standard_layout;
    template <class T> struct is_literal_type;
    template <class T> struct is_empty;
    template <class T> struct is_polymorphic;
    template <class T> struct is_abstract;

    template <class T, class... Args> struct is_constructible;
    template <class T>                struct is_default_constructible;
    template <class T>                struct is_copy_constructible;
    template <class T>                struct is_move_constructible;
    template <class T, class U>       struct is_assignable;
    template <class T>                struct is_copy_assignable;
    template <class T>                struct is_move_assignable;
    template <class T>                struct is_destructible;

    template <class T, class... Args> struct is_trivially_constructible;
    template <class T>                struct is_trivially_default_constructible;
    template <class T>                struct is_trivially_copy_constructible;
    template <class T>                struct is_trivially_move_constructible;
    template <class T, class U>       struct is_trivially_assignable;
    template <class T>                struct is_trivially_copy_assignable;
    template <class T>                struct is_trivially_move_assignable;
    template <class T>                struct is_trivially_destructible;

    template <class T, class... Args> struct is_nothrow_constructible;
    template <class T>                struct is_nothrow_default_constructible;
    template <class T>                struct is_nothrow_copy_constructible;
    template <class T>                struct is_nothrow_move_constructible;
    template <class T, class U>       struct is_nothrow_assignable;
    template <class T>                struct is_nothrow_copy_assignable;
    template <class T>                struct is_nothrow_move_assignable;
    template <class T>                struct is_nothrow_destructible;

    template <class T> struct has_virtual_destructor;

    // Relationships between types:
    template <class T, class U> struct is_same;
    template <class Base, class Derived> struct is_base_of;
    template <class From, class To> struct is_convertible;

    // Alignment properties and transformations:
    template <class T> struct alignment_of;
    template <size_t Len, size_t Align = most_stringent_alignment_requirement>
        struct aligned_storage;

    template <class T> struct decay;
    template <class... T> struct common_type;
    template <class T> struct underlying_type;
    template <class> class result_of; // undefined
    template <class Fn, class... ArgTypes> class result_of<Fn(ArgTypes...)>;

}  // std

*/
#include <__config>
#include <cstddef>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

template <bool _Bp, class _If, class _Then>
    struct _LIBCPP_VISIBLE conditional {typedef _If type;};
template <class _If, class _Then>
    struct _LIBCPP_VISIBLE conditional<false, _If, _Then> {typedef _Then type;};

template <bool, class _Tp = void> struct _LIBCPP_VISIBLE enable_if {};
template <class _Tp> struct _LIBCPP_VISIBLE enable_if<true, _Tp> {typedef _Tp type;};

struct __two {char _[2];};

// helper class:

template <class _Tp, _Tp __v>
struct _LIBCPP_VISIBLE integral_constant
{
    static _LIBCPP_CONSTEXPR const _Tp      value = __v;
    typedef _Tp               value_type;
    typedef integral_constant type;
    _LIBCPP_INLINE_VISIBILITY
        _LIBCPP_CONSTEXPR operator value_type() const {return value;}
};

template <class _Tp, _Tp __v>
_LIBCPP_CONSTEXPR const _Tp integral_constant<_Tp, __v>::value;

typedef integral_constant<bool, true>  true_type;
typedef integral_constant<bool, false> false_type;

// is_const

template <class _Tp> struct _LIBCPP_VISIBLE is_const            : public false_type {};
template <class _Tp> struct _LIBCPP_VISIBLE is_const<_Tp const> : public true_type {};

// is_volatile

template <class _Tp> struct _LIBCPP_VISIBLE is_volatile               : public false_type {};
template <class _Tp> struct _LIBCPP_VISIBLE is_volatile<_Tp volatile> : public true_type {};

// remove_const

template <class _Tp> struct _LIBCPP_VISIBLE remove_const            {typedef _Tp type;};
template <class _Tp> struct _LIBCPP_VISIBLE remove_const<const _Tp> {typedef _Tp type;};

// remove_volatile

template <class _Tp> struct _LIBCPP_VISIBLE remove_volatile               {typedef _Tp type;};
template <class _Tp> struct _LIBCPP_VISIBLE remove_volatile<volatile _Tp> {typedef _Tp type;};

// remove_cv

template <class _Tp> struct _LIBCPP_VISIBLE remove_cv
{typedef typename remove_volatile<typename remove_const<_Tp>::type>::type type;};

// is_void

template <class _Tp> struct __is_void       : public false_type {};
template <>          struct __is_void<void> : public true_type {};

template <class _Tp> struct _LIBCPP_VISIBLE is_void
    : public __is_void<typename remove_cv<_Tp>::type> {};

// __is_nullptr_t

template <class _Tp> struct ____is_nullptr_t       : public false_type {};
template <>          struct ____is_nullptr_t<nullptr_t> : public true_type {};

template <class _Tp> struct _LIBCPP_VISIBLE __is_nullptr_t
    : public ____is_nullptr_t<typename remove_cv<_Tp>::type> {};

// is_integral

template <class _Tp> struct __is_integral                     : public false_type {};
template <>          struct __is_integral<bool>               : public true_type {};
template <>          struct __is_integral<char>               : public true_type {};
template <>          struct __is_integral<signed char>        : public true_type {};
template <>          struct __is_integral<unsigned char>      : public true_type {};
template <>          struct __is_integral<wchar_t>            : public true_type {};
#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
template <>          struct __is_integral<char16_t>           : public true_type {};
template <>          struct __is_integral<char32_t>           : public true_type {};
#endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
template <>          struct __is_integral<short>              : public true_type {};
template <>          struct __is_integral<unsigned short>     : public true_type {};
template <>          struct __is_integral<int>                : public true_type {};
template <>          struct __is_integral<unsigned int>       : public true_type {};
template <>          struct __is_integral<long>               : public true_type {};
template <>          struct __is_integral<unsigned long>      : public true_type {};
template <>          struct __is_integral<long long>          : public true_type {};
template <>          struct __is_integral<unsigned long long> : public true_type {};

template <class _Tp> struct _LIBCPP_VISIBLE is_integral
    : public __is_integral<typename remove_cv<_Tp>::type> {};

// is_floating_point

template <class _Tp> struct __is_floating_point              : public false_type {};
template <>          struct __is_floating_point<float>       : public true_type {};
template <>          struct __is_floating_point<double>      : public true_type {};
template <>          struct __is_floating_point<long double> : public true_type {};

template <class _Tp> struct _LIBCPP_VISIBLE is_floating_point
    : public __is_floating_point<typename remove_cv<_Tp>::type> {};

// is_array

template <class _Tp> struct _LIBCPP_VISIBLE is_array
    : public false_type {};
template <class _Tp> struct _LIBCPP_VISIBLE is_array<_Tp[]>
    : public true_type {};
template <class _Tp, size_t _Np> struct _LIBCPP_VISIBLE is_array<_Tp[_Np]>
    : public true_type {};

// is_pointer

template <class _Tp> struct __is_pointer       : public false_type {};
template <class _Tp> struct __is_pointer<_Tp*> : public true_type {};

template <class _Tp> struct _LIBCPP_VISIBLE is_pointer
    : public __is_pointer<typename remove_cv<_Tp>::type> {};

// is_reference

template <class _Tp> struct _LIBCPP_VISIBLE is_lvalue_reference       : public false_type {};
template <class _Tp> struct _LIBCPP_VISIBLE is_lvalue_reference<_Tp&> : public true_type {};

template <class _Tp> struct _LIBCPP_VISIBLE is_rvalue_reference        : public false_type {};
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
template <class _Tp> struct _LIBCPP_VISIBLE is_rvalue_reference<_Tp&&> : public true_type {};
#endif

template <class _Tp> struct _LIBCPP_VISIBLE is_reference        : public false_type {};
template <class _Tp> struct _LIBCPP_VISIBLE is_reference<_Tp&>  : public true_type {};
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
template <class _Tp> struct _LIBCPP_VISIBLE is_reference<_Tp&&> : public true_type {};
#endif

#if defined(__clang__) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
#define _LIBCPP_HAS_TYPE_TRAITS
#endif

// is_union

#if __has_feature(is_union) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)

template <class _Tp> struct _LIBCPP_VISIBLE is_union
    : public integral_constant<bool, __is_union(_Tp)> {};

#else

template <class _Tp> struct __libcpp_union : public false_type {};
template <class _Tp> struct _LIBCPP_VISIBLE is_union
    : public __libcpp_union<typename remove_cv<_Tp>::type> {};

#endif

// is_class

#if __has_feature(is_class) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)

template <class _Tp> struct _LIBCPP_VISIBLE is_class
    : public integral_constant<bool, __is_class(_Tp)> {};

#else

namespace __is_class_imp
{
template <class _Tp> char  __test(int _Tp::*);
template <class _Tp> __two __test(...);
}

template <class _Tp> struct _LIBCPP_VISIBLE is_class
    : public integral_constant<bool, sizeof(__is_class_imp::__test<_Tp>(0)) == 1 && !is_union<_Tp>::value> {};

#endif

// is_same

template <class _Tp, class _Up> struct _LIBCPP_VISIBLE is_same           : public false_type {};
template <class _Tp>            struct _LIBCPP_VISIBLE is_same<_Tp, _Tp> : public true_type {};

// is_function

namespace __is_function_imp
{
template <class _Tp> char  __test(_Tp*);
template <class _Tp> __two __test(...);
template <class _Tp> _Tp&  __source();
}

template <class _Tp, bool = is_class<_Tp>::value ||
                            is_union<_Tp>::value ||
                            is_void<_Tp>::value  ||
                            is_reference<_Tp>::value ||
                            is_same<_Tp, nullptr_t>::value >
struct __is_function
    : public integral_constant<bool, sizeof(__is_function_imp::__test<_Tp>(__is_function_imp::__source<_Tp>())) == 1>
    {};
template <class _Tp> struct __is_function<_Tp, true> : public false_type {};

template <class _Tp> struct _LIBCPP_VISIBLE is_function
    : public __is_function<_Tp> {};

// is_member_function_pointer

template <class _Tp> struct            __is_member_function_pointer             : public false_type {};
template <class _Tp, class _Up> struct __is_member_function_pointer<_Tp _Up::*> : public is_function<_Tp> {};

template <class _Tp> struct _LIBCPP_VISIBLE is_member_function_pointer
    : public __is_member_function_pointer<typename remove_cv<_Tp>::type> {};

// is_member_pointer

template <class _Tp>            struct __is_member_pointer             : public false_type {};
template <class _Tp, class _Up> struct __is_member_pointer<_Tp _Up::*> : public true_type {};

template <class _Tp> struct _LIBCPP_VISIBLE is_member_pointer
    : public __is_member_pointer<typename remove_cv<_Tp>::type> {};

// is_member_object_pointer

template <class _Tp> struct _LIBCPP_VISIBLE is_member_object_pointer
    : public integral_constant<bool, is_member_pointer<_Tp>::value &&
                                    !is_member_function_pointer<_Tp>::value> {};

// is_enum

#if __has_feature(is_enum) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)

template <class _Tp> struct _LIBCPP_VISIBLE is_enum
    : public integral_constant<bool, __is_enum(_Tp)> {};

#else

template <class _Tp> struct _LIBCPP_VISIBLE is_enum
    : public integral_constant<bool, !is_void<_Tp>::value             &&
                                     !is_integral<_Tp>::value         &&
                                     !is_floating_point<_Tp>::value   &&
                                     !is_array<_Tp>::value            &&
                                     !is_pointer<_Tp>::value          &&
                                     !is_reference<_Tp>::value        &&
                                     !is_member_pointer<_Tp>::value   &&
                                     !is_union<_Tp>::value            &&
                                     !is_class<_Tp>::value            &&
                                     !is_function<_Tp>::value         > {};

#endif

// is_arithmetic

template <class _Tp> struct _LIBCPP_VISIBLE is_arithmetic
    : public integral_constant<bool, is_integral<_Tp>::value      ||
                                     is_floating_point<_Tp>::value> {};

// is_fundamental

template <class _Tp> struct _LIBCPP_VISIBLE is_fundamental
    : public integral_constant<bool, is_void<_Tp>::value        ||
                                     __is_nullptr_t<_Tp>::value ||
                                     is_arithmetic<_Tp>::value> {};

// is_scalar

template <class _Tp> struct _LIBCPP_VISIBLE is_scalar
    : public integral_constant<bool, is_arithmetic<_Tp>::value     ||
                                     is_member_pointer<_Tp>::value ||
                                     is_pointer<_Tp>::value        ||
                                     __is_nullptr_t<_Tp>::value    ||
                                     is_enum<_Tp>::value           > {};

template <> struct _LIBCPP_VISIBLE is_scalar<nullptr_t> : public true_type {};

// is_object

template <class _Tp> struct _LIBCPP_VISIBLE is_object
    : public integral_constant<bool, is_scalar<_Tp>::value ||
                                     is_array<_Tp>::value  ||
                                     is_union<_Tp>::value  ||
                                     is_class<_Tp>::value  > {};

// is_compound

template <class _Tp> struct _LIBCPP_VISIBLE is_compound
    : public integral_constant<bool, !is_fundamental<_Tp>::value> {};

// add_const

template <class _Tp, bool = is_reference<_Tp>::value ||
                            is_function<_Tp>::value  ||
                            is_const<_Tp>::value     >
struct __add_const             {typedef _Tp type;};

template <class _Tp>
struct __add_const<_Tp, false> {typedef const _Tp type;};

template <class _Tp> struct _LIBCPP_VISIBLE add_const
    {typedef typename __add_const<_Tp>::type type;};

// add_volatile

template <class _Tp, bool = is_reference<_Tp>::value ||
                            is_function<_Tp>::value  ||
                            is_volatile<_Tp>::value  >
struct __add_volatile             {typedef _Tp type;};

template <class _Tp>
struct __add_volatile<_Tp, false> {typedef volatile _Tp type;};

template <class _Tp> struct _LIBCPP_VISIBLE add_volatile
    {typedef typename __add_volatile<_Tp>::type type;};

// add_cv

template <class _Tp> struct _LIBCPP_VISIBLE add_cv
    {typedef typename add_const<typename add_volatile<_Tp>::type>::type type;};

// remove_reference

template <class _Tp> struct _LIBCPP_VISIBLE remove_reference        {typedef _Tp type;};
template <class _Tp> struct _LIBCPP_VISIBLE remove_reference<_Tp&>  {typedef _Tp type;};
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
template <class _Tp> struct _LIBCPP_VISIBLE remove_reference<_Tp&&> {typedef _Tp type;};
#endif

// add_lvalue_reference

template <class _Tp> struct _LIBCPP_VISIBLE add_lvalue_reference                      {typedef _Tp& type;};
template <class _Tp> struct _LIBCPP_VISIBLE add_lvalue_reference<_Tp&>                {typedef _Tp& type;};  // for older compiler
template <>          struct _LIBCPP_VISIBLE add_lvalue_reference<void>                {typedef void type;};
template <>          struct _LIBCPP_VISIBLE add_lvalue_reference<const void>          {typedef const void type;};
template <>          struct _LIBCPP_VISIBLE add_lvalue_reference<volatile void>       {typedef volatile void type;};
template <>          struct _LIBCPP_VISIBLE add_lvalue_reference<const volatile void> {typedef const volatile void type;};

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Tp> struct _LIBCPP_VISIBLE  add_rvalue_reference                     {typedef _Tp&& type;};
template <>          struct _LIBCPP_VISIBLE add_rvalue_reference<void>                {typedef void type;};
template <>          struct _LIBCPP_VISIBLE add_rvalue_reference<const void>          {typedef const void type;};
template <>          struct _LIBCPP_VISIBLE add_rvalue_reference<volatile void>       {typedef volatile void type;};
template <>          struct _LIBCPP_VISIBLE add_rvalue_reference<const volatile void> {typedef const volatile void type;};

#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Tp>
typename add_rvalue_reference<_Tp>::type
declval() _NOEXCEPT;

#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Tp>
typename add_lvalue_reference<_Tp>::type
declval();

#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES

struct __any
{
    __any(...);
};

// remove_pointer

template <class _Tp> struct _LIBCPP_VISIBLE remove_pointer                      {typedef _Tp type;};
template <class _Tp> struct _LIBCPP_VISIBLE remove_pointer<_Tp*>                {typedef _Tp type;};
template <class _Tp> struct _LIBCPP_VISIBLE remove_pointer<_Tp* const>          {typedef _Tp type;};
template <class _Tp> struct _LIBCPP_VISIBLE remove_pointer<_Tp* volatile>       {typedef _Tp type;};
template <class _Tp> struct _LIBCPP_VISIBLE remove_pointer<_Tp* const volatile> {typedef _Tp type;};

// add_pointer

template <class _Tp> struct _LIBCPP_VISIBLE add_pointer
    {typedef typename remove_reference<_Tp>::type* type;};

// is_signed

template <class _Tp, bool = is_integral<_Tp>::value>
struct ___is_signed : public integral_constant<bool, _Tp(-1) < _Tp(0)> {};

template <class _Tp>
struct ___is_signed<_Tp, false> : public true_type {};  // floating point

template <class _Tp, bool = is_arithmetic<_Tp>::value>
struct __is_signed : public ___is_signed<_Tp> {};

template <class _Tp> struct __is_signed<_Tp, false> : public false_type {};

template <class _Tp> struct _LIBCPP_VISIBLE is_signed : public __is_signed<_Tp> {};

// is_unsigned

template <class _Tp, bool = is_integral<_Tp>::value>
struct ___is_unsigned : public integral_constant<bool, _Tp(0) < _Tp(-1)> {};

template <class _Tp>
struct ___is_unsigned<_Tp, false> : public false_type {};  // floating point

template <class _Tp, bool = is_arithmetic<_Tp>::value>
struct __is_unsigned : public ___is_unsigned<_Tp> {};

template <class _Tp> struct __is_unsigned<_Tp, false> : public false_type {};

template <class _Tp> struct _LIBCPP_VISIBLE is_unsigned : public __is_unsigned<_Tp> {};

// rank

template <class _Tp> struct _LIBCPP_VISIBLE rank
    : public integral_constant<size_t, 0> {};
template <class _Tp> struct _LIBCPP_VISIBLE rank<_Tp[]>
    : public integral_constant<size_t, rank<_Tp>::value + 1> {};
template <class _Tp, size_t _Np> struct _LIBCPP_VISIBLE rank<_Tp[_Np]>
    : public integral_constant<size_t, rank<_Tp>::value + 1> {};

// extent

template <class _Tp, unsigned _Ip = 0> struct _LIBCPP_VISIBLE extent
    : public integral_constant<size_t, 0> {};
template <class _Tp> struct _LIBCPP_VISIBLE extent<_Tp[], 0>
    : public integral_constant<size_t, 0> {};
template <class _Tp, unsigned _Ip> struct _LIBCPP_VISIBLE extent<_Tp[], _Ip>
    : public integral_constant<size_t, extent<_Tp, _Ip-1>::value> {};
template <class _Tp, size_t _Np> struct _LIBCPP_VISIBLE extent<_Tp[_Np], 0>
    : public integral_constant<size_t, _Np> {};
template <class _Tp, size_t _Np, unsigned _Ip> struct _LIBCPP_VISIBLE extent<_Tp[_Np], _Ip>
    : public integral_constant<size_t, extent<_Tp, _Ip-1>::value> {};

// remove_extent

template <class _Tp> struct _LIBCPP_VISIBLE remove_extent
    {typedef _Tp type;};
template <class _Tp> struct _LIBCPP_VISIBLE remove_extent<_Tp[]>
    {typedef _Tp type;};
template <class _Tp, size_t _Np> struct _LIBCPP_VISIBLE remove_extent<_Tp[_Np]>
    {typedef _Tp type;};

// remove_all_extents

template <class _Tp> struct _LIBCPP_VISIBLE remove_all_extents
    {typedef _Tp type;};
template <class _Tp> struct _LIBCPP_VISIBLE remove_all_extents<_Tp[]>
    {typedef typename remove_all_extents<_Tp>::type type;};
template <class _Tp, size_t _Np> struct _LIBCPP_VISIBLE remove_all_extents<_Tp[_Np]>
    {typedef typename remove_all_extents<_Tp>::type type;};

// is_abstract

namespace __is_abstract_imp
{
template <class _Tp> char  __test(_Tp (*)[1]);
template <class _Tp> __two __test(...);
}

template <class _Tp, bool = is_class<_Tp>::value>
struct __libcpp_abstract : public integral_constant<bool, sizeof(__is_abstract_imp::__test<_Tp>(0)) != 1> {};

template <class _Tp> struct __libcpp_abstract<_Tp, false> : public false_type {};

template <class _Tp> struct _LIBCPP_VISIBLE is_abstract : public __libcpp_abstract<_Tp> {};

// is_convertible

#if __has_feature(is_convertible_to)

template <class _T1, class _T2> struct _LIBCPP_VISIBLE is_convertible
    : public integral_constant<bool, __is_convertible_to(_T1, _T2)> {};

#else  // __has_feature(is_convertible_to)

namespace __is_convertible_imp
{
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
template <class _Tp> char  __test(const volatile typename remove_reference<_Tp>::type&&);
#else
template <class _Tp> char  __test(_Tp);
#endif
template <class _Tp> __two __test(...);
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
template <class _Tp> _Tp&& __source();
#else
template <class _Tp> typename remove_reference<_Tp>::type& __source();
#endif

template <class _Tp, bool _IsArray =    is_array<_Tp>::value,
                     bool _IsFunction = is_function<_Tp>::value,
                     bool _IsVoid =     is_void<_Tp>::value>
                     struct __is_array_function_or_void                          {enum {value = 0};};
template <class _Tp> struct __is_array_function_or_void<_Tp, true, false, false> {enum {value = 1};};
template <class _Tp> struct __is_array_function_or_void<_Tp, false, true, false> {enum {value = 2};};
template <class _Tp> struct __is_array_function_or_void<_Tp, false, false, true> {enum {value = 3};};
}

template <class _Tp,
    unsigned = __is_convertible_imp::__is_array_function_or_void<typename remove_reference<_Tp>::type>::value>
struct __is_convertible_check
{
    static const size_t __v = 0;
};

template <class _Tp>
struct __is_convertible_check<_Tp, 0>
{
    static const size_t __v = sizeof(_Tp);
};

template <class _T1, class _T2,
    unsigned _T1_is_array_function_or_void = __is_convertible_imp::__is_array_function_or_void<_T1>::value,
    unsigned _T2_is_array_function_or_void = __is_convertible_imp::__is_array_function_or_void<_T2>::value>
struct __is_convertible
    : public integral_constant<bool,
        sizeof(__is_convertible_imp::__test<_T2>(__is_convertible_imp::__source<_T1>())) == 1
    >
{};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 1, 0> : false_type {};

template <class _T1> struct __is_convertible<_T1, const _T1&, 1, 0> : true_type {};
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
template <class _T1> struct __is_convertible<_T1, _T1&&, 1, 0> : true_type {};
template <class _T1> struct __is_convertible<_T1, const _T1&&, 1, 0> : true_type {};
template <class _T1> struct __is_convertible<_T1, volatile _T1&&, 1, 0> : true_type {};
template <class _T1> struct __is_convertible<_T1, const volatile _T1&&, 1, 0> : true_type {};
#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _T1, class _T2> struct __is_convertible<_T1, _T2*, 1, 0>
    : public integral_constant<bool, __is_convertible<typename remove_all_extents<_T1>::type*, _T2*>::value> {};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2* const, 1, 0>
    : public integral_constant<bool, __is_convertible<typename remove_all_extents<_T1>::type*, _T2*const>::value> {};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2* volatile, 1, 0>
    : public integral_constant<bool, __is_convertible<typename remove_all_extents<_T1>::type*, _T2*volatile>::value> {};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2* const volatile, 1, 0>
    : public integral_constant<bool, __is_convertible<typename remove_all_extents<_T1>::type*, _T2*const volatile>::value> {};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 2, 0>                : public false_type {};
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
template <class _T1>            struct __is_convertible<_T1, _T1&&, 2, 0>               : public true_type {};
#endif
template <class _T1>            struct __is_convertible<_T1, _T1*, 2, 0>               : public true_type {};
template <class _T1>            struct __is_convertible<_T1, _T1*const, 2, 0>          : public true_type {};
template <class _T1>            struct __is_convertible<_T1, _T1*volatile, 2, 0>       : public true_type {};
template <class _T1>            struct __is_convertible<_T1, _T1*const volatile, 2, 0> : public true_type {};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 3, 0> : public false_type {};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 0, 1> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 1, 1> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 2, 1> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 3, 1> : public false_type {};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 0, 2> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 1, 2> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 2, 2> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 3, 2> : public false_type {};

template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 0, 3> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 1, 3> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 2, 3> : public false_type {};
template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 3, 3> : public true_type {};

template <class _T1, class _T2> struct _LIBCPP_VISIBLE is_convertible
    : public __is_convertible<_T1, _T2>
{
    static const size_t __complete_check1 = __is_convertible_check<_T1>::__v;
    static const size_t __complete_check2 = __is_convertible_check<_T2>::__v;
};

#endif  // __has_feature(is_convertible_to)

// is_base_of

#ifdef _LIBCP_HAS_IS_BASE_OF

template <class _Bp, class _Dp>
struct _LIBCPP_VISIBLE is_base_of
    : public integral_constant<bool, __is_base_of(_Bp, _Dp)> {};

#else  // __has_feature(is_base_of)

#error is_base_of not implemented.

#endif  // __has_feature(is_base_of)

// is_empty

#if __has_feature(is_empty)

template <class _Tp>
struct _LIBCPP_VISIBLE is_empty
    : public integral_constant<bool, __is_empty(_Tp)> {};

#else  // __has_feature(is_empty)

template <class _Tp>
struct __is_empty1
    : public _Tp
{
    double _;
};

struct __is_empty2
{
    double _;
};

template <class _Tp, bool = is_class<_Tp>::value>
struct __libcpp_empty : public integral_constant<bool, sizeof(__is_empty1<_Tp>) == sizeof(__is_empty2)> {};

template <class _Tp> struct __libcpp_empty<_Tp, false> : public false_type {};

template <class _Tp> struct _LIBCPP_VISIBLE is_empty : public __libcpp_empty<_Tp> {};

#endif  // __has_feature(is_empty)

// is_polymorphic

#if __has_feature(is_polymorphic)

template <class _Tp>
struct _LIBCPP_VISIBLE is_polymorphic
    : public integral_constant<bool, __is_polymorphic(_Tp)> {};

#else

template <class _Tp> struct __is_polymorphic1 : public _Tp {};
template <class _Tp> struct __is_polymorphic2 : public _Tp {virtual ~__is_polymorphic2() throw();};

template <class _Tp, bool = is_class<_Tp>::value>
struct __libcpp_polymorphic
    : public integral_constant<bool, sizeof(__is_polymorphic1<_Tp>) == sizeof(__is_polymorphic2<_Tp>)> {};

template <class _Tp> struct __libcpp_polymorphic<_Tp, false> : public false_type {};

template <class _Tp> struct _LIBCPP_VISIBLE is_polymorphic
    : public __libcpp_polymorphic<_Tp> {};

#endif // __has_feature(is_polymorphic)

// has_virtual_destructor

#if __has_feature(has_virtual_destructor) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)

template <class _Tp> struct _LIBCPP_VISIBLE has_virtual_destructor
    : public integral_constant<bool, __has_virtual_destructor(_Tp)> {};

#else  // _LIBCPP_HAS_TYPE_TRAITS

template <class _Tp> struct _LIBCPP_VISIBLE has_virtual_destructor
    : public false_type {};

#endif  // _LIBCPP_HAS_TYPE_TRAITS

// alignment_of

template <class _Tp> struct __alignment_of {_Tp _;};

template <class _Tp> struct _LIBCPP_VISIBLE alignment_of
    : public integral_constant<size_t, __alignof__(__alignment_of<typename remove_all_extents<_Tp>::type>)> {};

// aligned_storage

template <class _Hp, class _Tp>
struct __type_list
{
    typedef _Hp _Head;
    typedef _Tp _Tail;
};

struct __nat
{
#ifndef _LIBCPP_HAS_NO_DELETED_FUNCTIONS
    __nat() = delete;
    __nat(const __nat&) = delete;
    __nat& operator=(const __nat&) = delete;
    ~__nat() = delete;
#endif
};

template <class _Tp>
struct __align_type
{
    static const size_t value = alignment_of<_Tp>::value;
    typedef _Tp type;
};

struct __struct_double {long double _;};
struct __struct_double4 {double _[4];};

typedef
    __type_list<__align_type<unsigned char>,
    __type_list<__align_type<unsigned short>,
    __type_list<__align_type<unsigned int>,
    __type_list<__align_type<unsigned long>,
    __type_list<__align_type<unsigned long long>,
    __type_list<__align_type<double>,
    __type_list<__align_type<long double>,
    __type_list<__align_type<__struct_double>,
    __type_list<__align_type<__struct_double4>,
    __type_list<__align_type<int*>,
    __nat
    > > > > > > > > > > __all_types;

template <class _TL, size_t _Align> struct __find_pod;

template <class _Hp, size_t _Align>
struct __find_pod<__type_list<_Hp, __nat>, _Align>
{
    typedef typename conditional<
                             _Align == _Hp::value,
                             typename _Hp::type,
                             void
                         >::type type;
};

template <class _Hp, class _Tp, size_t _Align>
struct __find_pod<__type_list<_Hp, _Tp>, _Align>
{
    typedef typename conditional<
                             _Align == _Hp::value,
                             typename _Hp::type,
                             typename __find_pod<_Tp, _Align>::type
                         >::type type;
};

template <class _TL, size_t _Len> struct __find_max_align;

template <class _Hp, size_t _Len>
struct __find_max_align<__type_list<_Hp, __nat>, _Len> : public integral_constant<size_t, _Hp::value> {};

template <size_t _Len, size_t _A1, size_t _A2>
struct __select_align
{
private:
    static const size_t __min = _A2 < _A1 ? _A2 : _A1;
    static const size_t __max = _A1 < _A2 ? _A2 : _A1;
public:
    static const size_t value = _Len < __max ? __min : __max;
};

template <class _Hp, class _Tp, size_t _Len>
struct __find_max_align<__type_list<_Hp, _Tp>, _Len>
    : public integral_constant<size_t, __select_align<_Len, _Hp::value, __find_max_align<_Tp, _Len>::value>::value> {};

template <size_t _Len, const size_t _Align = __find_max_align<__all_types, _Len>::value>
struct _LIBCPP_VISIBLE aligned_storage
{
    typedef typename __find_pod<__all_types, _Align>::type _Aligner;
    static_assert(!is_void<_Aligner>::value, "");
    union type
    {
        _Aligner __align;
        unsigned char __data[_Len];
    };
};

#define _CREATE_ALIGNED_STORAGE_SPECIALIZATION(n) \
template <size_t _Len>\
struct _LIBCPP_VISIBLE aligned_storage<_Len, n>\
{\
    struct _ALIGNAS(n) type\
    {\
        unsigned char _[_Len];\
    };\
}

_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x1);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x2);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x4);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x8);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x10);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x20);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x40);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x80);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x100);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x200);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x400);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x800);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x1000);
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x2000);
// MSDN says that MSVC does not support alignment beyond 8192 (=0x2000)
#if !defined(_MSC_VER)
_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x4000);
#endif // !_MSC_VER

#undef _CREATE_ALIGNED_STORAGE_SPECIALIZATION

// __promote

template <class _A1, class _A2 = void, class _A3 = void,
          bool = (is_arithmetic<_A1>::value || is_void<_A1>::value) &&
                 (is_arithmetic<_A2>::value || is_void<_A2>::value) &&
                 (is_arithmetic<_A3>::value || is_void<_A3>::value)>
class __promote {};

template <class _A1, class _A2, class _A3>
class __promote<_A1, _A2, _A3, true>
{
private:
    typedef typename __promote<_A1>::type __type1;
    typedef typename __promote<_A2>::type __type2;
    typedef typename __promote<_A3>::type __type3;
public:
    typedef decltype(__type1() + __type2() + __type3()) type;
};

template <class _A1, class _A2>
class __promote<_A1, _A2, void, true>
{
private:
    typedef typename __promote<_A1>::type __type1;
    typedef typename __promote<_A2>::type __type2;
public:
    typedef decltype(__type1() + __type2()) type;
};

template <class _A1>
class __promote<_A1, void, void, true>
{
public:
    typedef typename conditional<is_arithmetic<_A1>::value,
                     typename conditional<is_integral<_A1>::value, double, _A1>::type,
                     void
            >::type type;
};

#ifdef _LIBCPP_STORE_AS_OPTIMIZATION

// __transform

template <class _Tp, size_t = sizeof(_Tp), bool = is_scalar<_Tp>::value> struct __transform {typedef _Tp type;};
template <class _Tp> struct __transform<_Tp, 1, true> {typedef unsigned char      type;};
template <class _Tp> struct __transform<_Tp, 2, true> {typedef unsigned short     type;};
template <class _Tp> struct __transform<_Tp, 4, true> {typedef unsigned int       type;};
template <class _Tp> struct __transform<_Tp, 8, true> {typedef unsigned long long type;};

#endif  // _LIBCPP_STORE_AS_OPTIMIZATION

// make_signed / make_unsigned

typedef
    __type_list<signed char,
    __type_list<signed short,
    __type_list<signed int,
    __type_list<signed long,
    __type_list<signed long long,
    __nat
    > > > > > __signed_types;

typedef
    __type_list<unsigned char,
    __type_list<unsigned short,
    __type_list<unsigned int,
    __type_list<unsigned long,
    __type_list<unsigned long long,
    __nat
    > > > > > __unsigned_types;

template <class _TypeList, size_t _Size, bool = _Size <= sizeof(typename _TypeList::_Head)> struct __find_first;

template <class _Hp, class _Tp, size_t _Size>
struct __find_first<__type_list<_Hp, _Tp>, _Size, true>
{
    typedef _Hp type;
};

template <class _Hp, class _Tp, size_t _Size>
struct __find_first<__type_list<_Hp, _Tp>, _Size, false>
{
    typedef typename __find_first<_Tp, _Size>::type type;
};

template <class _Tp, class _Up, bool = is_const<typename remove_reference<_Tp>::type>::value,
                             bool = is_volatile<typename remove_reference<_Tp>::type>::value>
struct __apply_cv
{
    typedef _Up type;
};

template <class _Tp, class _Up>
struct __apply_cv<_Tp, _Up, true, false>
{
    typedef const _Up type;
};

template <class _Tp, class _Up>
struct __apply_cv<_Tp, _Up, false, true>
{
    typedef volatile _Up type;
};

template <class _Tp, class _Up>
struct __apply_cv<_Tp, _Up, true, true>
{
    typedef const volatile _Up type;
};

template <class _Tp, class _Up>
struct __apply_cv<_Tp&, _Up, false, false>
{
    typedef _Up& type;
};

template <class _Tp, class _Up>
struct __apply_cv<_Tp&, _Up, true, false>
{
    typedef const _Up& type;
};

template <class _Tp, class _Up>
struct __apply_cv<_Tp&, _Up, false, true>
{
    typedef volatile _Up& type;
};

template <class _Tp, class _Up>
struct __apply_cv<_Tp&, _Up, true, true>
{
    typedef const volatile _Up& type;
};

template <class _Tp, bool = is_integral<_Tp>::value || is_enum<_Tp>::value>
struct __make_signed {};

template <class _Tp>
struct __make_signed<_Tp, true>
{
    typedef typename __find_first<__signed_types, sizeof(_Tp)>::type type;
};

template <> struct __make_signed<bool,               true> {};
template <> struct __make_signed<  signed short,     true> {typedef short     type;};
template <> struct __make_signed<unsigned short,     true> {typedef short     type;};
template <> struct __make_signed<  signed int,       true> {typedef int       type;};
template <> struct __make_signed<unsigned int,       true> {typedef int       type;};
template <> struct __make_signed<  signed long,      true> {typedef long      type;};
template <> struct __make_signed<unsigned long,      true> {typedef long      type;};
template <> struct __make_signed<  signed long long, true> {typedef long long type;};
template <> struct __make_signed<unsigned long long, true> {typedef long long type;};

template <class _Tp>
struct _LIBCPP_VISIBLE make_signed
{
    typedef typename __apply_cv<_Tp, typename __make_signed<typename remove_cv<_Tp>::type>::type>::type type;
};

template <class _Tp, bool = is_integral<_Tp>::value || is_enum<_Tp>::value>
struct __make_unsigned {};

template <class _Tp>
struct __make_unsigned<_Tp, true>
{
    typedef typename __find_first<__unsigned_types, sizeof(_Tp)>::type type;
};

template <> struct __make_unsigned<bool,               true> {};
template <> struct __make_unsigned<  signed short,     true> {typedef unsigned short     type;};
template <> struct __make_unsigned<unsigned short,     true> {typedef unsigned short     type;};
template <> struct __make_unsigned<  signed int,       true> {typedef unsigned int       type;};
template <> struct __make_unsigned<unsigned int,       true> {typedef unsigned int       type;};
template <> struct __make_unsigned<  signed long,      true> {typedef unsigned long      type;};
template <> struct __make_unsigned<unsigned long,      true> {typedef unsigned long      type;};
template <> struct __make_unsigned<  signed long long, true> {typedef unsigned long long type;};
template <> struct __make_unsigned<unsigned long long, true> {typedef unsigned long long type;};

template <class _Tp>
struct _LIBCPP_VISIBLE make_unsigned
{
    typedef typename __apply_cv<_Tp, typename __make_unsigned<typename remove_cv<_Tp>::type>::type>::type type;
};

#ifdef _LIBCPP_HAS_NO_VARIADICS

template <class _Tp, class _Up = void, class V = void>
struct _LIBCPP_VISIBLE common_type
{
public:
    typedef typename common_type<typename common_type<_Tp, _Up>::type, V>::type type;
};

template <class _Tp>
struct _LIBCPP_VISIBLE common_type<_Tp, void, void>
{
public:
    typedef _Tp type;
};

template <class _Tp, class _Up>
struct _LIBCPP_VISIBLE common_type<_Tp, _Up, void>
{
private:
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
    static _Tp&& __t();
    static _Up&& __u();
#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
    static _Tp __t();
    static _Up __u();
#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
public:
    typedef typename remove_reference<decltype(true ? __t() : __u())>::type type;
};

#else  // _LIBCPP_HAS_NO_VARIADICS

template <class ..._Tp> struct common_type;

template <class _Tp>
struct _LIBCPP_VISIBLE common_type<_Tp>
{
    typedef _Tp type;
};

template <class _Tp, class _Up>
struct _LIBCPP_VISIBLE common_type<_Tp, _Up>
{
private:
    static _Tp&& __t();
    static _Up&& __u();
    static bool __f();
public:
    typedef typename remove_reference<decltype(__f() ? __t() : __u())>::type type;
};

template <class _Tp, class _Up, class ..._Vp>
struct _LIBCPP_VISIBLE common_type<_Tp, _Up, _Vp...>
{
    typedef typename common_type<typename common_type<_Tp, _Up>::type, _Vp...>::type type;
};

#endif  // _LIBCPP_HAS_NO_VARIADICS

// is_assignable

template <class _Tp, class _Arg>
decltype((_VSTD::declval<_Tp>() = _VSTD::declval<_Arg>(), true_type()))
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
__is_assignable_test(_Tp&&, _Arg&&);
#else
__is_assignable_test(_Tp, _Arg&);
#endif

template <class _Arg>
false_type
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
__is_assignable_test(__any, _Arg&&);
#else
__is_assignable_test(__any, _Arg&);
#endif

template <class _Tp, class _Arg, bool = is_void<_Tp>::value || is_void<_Arg>::value>
struct __is_assignable_imp
    : public common_type
        <
            decltype(__is_assignable_test(declval<_Tp>(), declval<_Arg>()))
        >::type {};

template <class _Tp, class _Arg>
struct __is_assignable_imp<_Tp, _Arg, true>
    : public false_type
{
};

template <class _Tp, class _Arg>
struct is_assignable
    : public __is_assignable_imp<_Tp, _Arg> {};

// is_copy_assignable

template <class _Tp> struct _LIBCPP_VISIBLE is_copy_assignable
    : public is_assignable<typename add_lvalue_reference<_Tp>::type,
                     const typename add_lvalue_reference<_Tp>::type> {};

// is_move_assignable

template <class _Tp> struct _LIBCPP_VISIBLE is_move_assignable
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
    : public is_assignable<typename add_lvalue_reference<_Tp>::type,
                     const typename add_rvalue_reference<_Tp>::type> {};
#else
    : public is_copy_assignable<_Tp> {};
#endif

// is_destructible

template <class _Tp>
struct __destructible_test
{
    _Tp __t;
};

template <class _Tp>
decltype((_VSTD::declval<__destructible_test<_Tp> >().~__destructible_test<_Tp>(), true_type()))
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
__is_destructible_test(_Tp&&);
#else
__is_destructible_test(_Tp&);
#endif

false_type
__is_destructible_test(__any);

template <class _Tp, bool = is_void<_Tp>::value || is_abstract<_Tp>::value>
struct __destructible_imp
    : public common_type
        <
            decltype(__is_destructible_test(declval<_Tp>()))
        >::type {};

template <class _Tp>
struct __destructible_imp<_Tp, true>
    : public false_type {};

template <class _Tp>
struct is_destructible
    : public __destructible_imp<_Tp> {};

// move

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
typename remove_reference<_Tp>::type&&
move(_Tp&& __t) _NOEXCEPT
{
    typedef typename remove_reference<_Tp>::type _Up;
    return static_cast<_Up&&>(__t);
}

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
_Tp&&
forward(typename std::remove_reference<_Tp>::type& __t) _NOEXCEPT
{
    return static_cast<_Tp&&>(__t);
}

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
_Tp&&
forward(typename std::remove_reference<_Tp>::type&& __t) _NOEXCEPT
{
    static_assert(!std::is_lvalue_reference<_Tp>::value,
                  "Can not forward an rvalue as an lvalue.");
    return static_cast<_Tp&&>(__t);
}

#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
_Tp&
move(_Tp& __t)
{
    return __t;
}

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
const _Tp&
move(const _Tp& __t)
{
    return __t;
}

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
_Tp&
forward(typename std::remove_reference<_Tp>::type& __t) _NOEXCEPT
{
    return __t;
}


template <class _Tp>
class __rv
{
    typedef typename remove_reference<_Tp>::type _Trr;
    _Trr& t_;
public:
    _LIBCPP_INLINE_VISIBILITY
    _Trr* operator->() {return &t_;}
    _LIBCPP_INLINE_VISIBILITY
    explicit __rv(_Trr& __t) : t_(__t) {}
};

#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Tp>
struct _LIBCPP_VISIBLE decay
{
private:
    typedef typename remove_reference<_Tp>::type _Up;
public:
    typedef typename conditional
                     <
                         is_array<_Up>::value,
                         typename remove_extent<_Up>::type*,
                         typename conditional
                         <
                              is_function<_Up>::value,
                              typename add_pointer<_Up>::type,
                              typename remove_cv<_Up>::type
                         >::type
                     >::type type;
};

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
typename decay<_Tp>::type
__decay_copy(_Tp&& __t)
{
    return _VSTD::forward<_Tp>(__t);
}

#else

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
typename decay<_Tp>::type
__decay_copy(const _Tp& __t)
{
    return _VSTD::forward<_Tp>(__t);
}

#endif

template <class _MP, bool _IsMemberFuctionPtr, bool _IsMemberObjectPtr>
struct __member_pointer_traits_imp
{
};

#ifndef _LIBCPP_HAS_NO_VARIADICS

template <class _Rp, class _Class, class ..._Param>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...), true, false>
{
    typedef _Class _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class ..._Param>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) const, true, false>
{
    typedef _Class const _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class ..._Param>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) volatile, true, false>
{
    typedef _Class volatile _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class ..._Param>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) const volatile, true, false>
{
    typedef _Class const volatile _ClassType;
    typedef _Rp _ReturnType;
};

#if __has_feature(cxx_reference_qualified_functions)

template <class _Rp, class _Class, class ..._Param>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) &, true, false>
{
    typedef _Class& _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class ..._Param>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) const&, true, false>
{
    typedef _Class const& _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class ..._Param>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) volatile&, true, false>
{
    typedef _Class volatile& _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class ..._Param>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) const volatile&, true, false>
{
    typedef _Class const volatile& _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class ..._Param>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) &&, true, false>
{
    typedef _Class&& _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class ..._Param>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) const&&, true, false>
{
    typedef _Class const&& _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class ..._Param>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) volatile&&, true, false>
{
    typedef _Class volatile&& _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class ..._Param>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...) const volatile&&, true, false>
{
    typedef _Class const volatile&& _ClassType;
    typedef _Rp _ReturnType;
};

#endif  // __has_feature(cxx_reference_qualified_functions)

#else  // _LIBCPP_HAS_NO_VARIADICS

template <class _Rp, class _Class>
struct __member_pointer_traits_imp<_Rp (_Class::*)(), true, false>
{
    typedef _Class _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class _P0>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0), true, false>
{
    typedef _Class _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class _P0, class _P1>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1), true, false>
{
    typedef _Class _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class _P0, class _P1, class _P2>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, _P2), true, false>
{
    typedef _Class _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class>
struct __member_pointer_traits_imp<_Rp (_Class::*)() const, true, false>
{
    typedef _Class const _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class _P0>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0) const, true, false>
{
    typedef _Class const _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class _P0, class _P1>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1) const, true, false>
{
    typedef _Class const _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class _P0, class _P1, class _P2>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, _P2) const, true, false>
{
    typedef _Class const _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class>
struct __member_pointer_traits_imp<_Rp (_Class::*)() volatile, true, false>
{
    typedef _Class volatile _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class _P0>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0) volatile, true, false>
{
    typedef _Class volatile _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class _P0, class _P1>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1) volatile, true, false>
{
    typedef _Class volatile _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class _P0, class _P1, class _P2>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, _P2) volatile, true, false>
{
    typedef _Class volatile _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class>
struct __member_pointer_traits_imp<_Rp (_Class::*)() const volatile, true, false>
{
    typedef _Class const volatile _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class _P0>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0) const volatile, true, false>
{
    typedef _Class const volatile _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class _P0, class _P1>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1) const volatile, true, false>
{
    typedef _Class const volatile _ClassType;
    typedef _Rp _ReturnType;
};

template <class _Rp, class _Class, class _P0, class _P1, class _P2>
struct __member_pointer_traits_imp<_Rp (_Class::*)(_P0, _P1, _P2) const volatile, true, false>
{
    typedef _Class const volatile _ClassType;
    typedef _Rp _ReturnType;
};

#endif  // _LIBCPP_HAS_NO_VARIADICS

template <class _Rp, class _Class>
struct __member_pointer_traits_imp<_Rp _Class::*, false, true>
{
    typedef _Class _ClassType;
    typedef _Rp _ReturnType;
};

template <class _MP>
struct __member_pointer_traits
    : public __member_pointer_traits_imp<_MP,
                    is_member_function_pointer<_MP>::value,
                    is_member_object_pointer<_MP>::value>
{
//     typedef ... _ClassType;
//     typedef ... _ReturnType;
};

// result_of

template <class _Callable> class result_of;

template <class _Fn, bool, bool>
class __result_of
{
};

#ifndef _LIBCPP_HAS_NO_VARIADICS

template <class _Fn, class ..._ArgTypes>
class __result_of<_Fn(_ArgTypes...), true, false>
{
public:
    typedef decltype(declval<_Fn>()(declval<_ArgTypes>()...)) type;
};

template <class _MP, class _Tp, bool _IsMemberFunctionPtr>
struct __result_of_mp;

// member function pointer

template <class _MP, class _Tp>
struct __result_of_mp<_MP, _Tp, true>
    : public common_type<typename __member_pointer_traits<_MP>::_ReturnType>
{
};

// member data pointer

template <class _MP, class _Tp, bool>
struct __result_of_mdp;

template <class _Rp, class _Class, class _Tp>
struct __result_of_mdp<_Rp _Class::*, _Tp, false>
{
    typedef typename __apply_cv<decltype(*_VSTD::declval<_Tp>()), _Rp>::type&& type;
};

template <class _Rp, class _Class, class _Tp>
struct __result_of_mdp<_Rp _Class::*, _Tp, true>
{
    typedef typename __apply_cv<_Tp, _Rp>::type&& type;
};

template <class _Rp, class _Class, class _Tp>
struct __result_of_mp<_Rp _Class::*, _Tp, false>
    : public __result_of_mdp<_Rp _Class::*, _Tp,
            is_base_of<_Class, typename remove_reference<_Tp>::type>::value>
{
};

template <class _Fn, class _Tp, class ..._ArgTypes>
class __result_of<_Fn(_Tp, _ArgTypes...), false, true>  // _Fn must be member pointer
    : public __result_of_mp<typename remove_reference<_Fn>::type,
                            _Tp,
                            is_member_function_pointer<typename remove_reference<_Fn>::type>::value>
{
};

// result_of

template <class _Fn, class ..._ArgTypes>
class _LIBCPP_VISIBLE result_of<_Fn(_ArgTypes...)>
    : public __result_of<_Fn(_ArgTypes...),
                         is_class<typename remove_reference<_Fn>::type>::value ||
                         is_function<typename remove_reference<_Fn>::type>::value,
                         is_member_pointer<typename remove_reference<_Fn>::type>::value
                        >
{
};

#else  // _LIBCPP_HAS_NO_VARIADICS

template <class _Fn>
class __result_of<_Fn(), true, false>
{
public:
    typedef decltype(declval<_Fn>()()) type;
};

template <class _Fn, class _A0>
class __result_of<_Fn(_A0), true, false>
{
public:
    typedef decltype(declval<_Fn>()(declval<_A0>())) type;
};

template <class _Fn, class _A0, class _A1>
class __result_of<_Fn(_A0, _A1), true, false>
{
public:
    typedef decltype(declval<_Fn>()(declval<_A0>(), declval<_A1>())) type;
};

template <class _Fn, class _A0, class _A1, class _A2>
class __result_of<_Fn(_A0, _A1, _A2), true, false>
{
public:
    typedef decltype(declval<_Fn>()(declval<_A0>(), declval<_A1>(), declval<_A2>())) type;
};

template <class _MP, class _Tp, bool _IsMemberFunctionPtr>
struct __result_of_mp;

// member function pointer

template <class _MP, class _Tp>
struct __result_of_mp<_MP, _Tp, true>
    : public common_type<typename __member_pointer_traits<_MP>::_ReturnType>
{
};

// member data pointer

template <class _MP, class _Tp, bool>
struct __result_of_mdp;

template <class _Rp, class _Class, class _Tp>
struct __result_of_mdp<_Rp _Class::*, _Tp, false>
{
    typedef typename __apply_cv<decltype(*_VSTD::declval<_Tp>()), _Rp>::type& type;
};

template <class _Rp, class _Class, class _Tp>
struct __result_of_mdp<_Rp _Class::*, _Tp, true>
{
    typedef typename __apply_cv<_Tp, _Rp>::type& type;
};

template <class _Rp, class _Class, class _Tp>
struct __result_of_mp<_Rp _Class::*, _Tp, false>
    : public __result_of_mdp<_Rp _Class::*, _Tp,
            is_base_of<_Class, typename remove_reference<_Tp>::type>::value>
{
};



template <class _Fn, class _Tp>
class __result_of<_Fn(_Tp), false, true>  // _Fn must be member pointer
    : public __result_of_mp<typename remove_reference<_Fn>::type,
                            _Tp,
                            is_member_function_pointer<typename remove_reference<_Fn>::type>::value>
{
};

template <class _Fn, class _Tp, class _A0>
class __result_of<_Fn(_Tp, _A0), false, true>  // _Fn must be member pointer
    : public __result_of_mp<typename remove_reference<_Fn>::type,
                            _Tp,
                            is_member_function_pointer<typename remove_reference<_Fn>::type>::value>
{
};

template <class _Fn, class _Tp, class _A0, class _A1>
class __result_of<_Fn(_Tp, _A0, _A1), false, true>  // _Fn must be member pointer
    : public __result_of_mp<typename remove_reference<_Fn>::type,
                            _Tp,
                            is_member_function_pointer<typename remove_reference<_Fn>::type>::value>
{
};

template <class _Fn, class _Tp, class _A0, class _A1, class _A2>
class __result_of<_Fn(_Tp, _A0, _A1, _A2), false, true>  // _Fn must be member pointer
    : public __result_of_mp<typename remove_reference<_Fn>::type,
                            _Tp,
                            is_member_function_pointer<typename remove_reference<_Fn>::type>::value>
{
};

// result_of

template <class _Fn>
class _LIBCPP_VISIBLE result_of<_Fn()>
    : public __result_of<_Fn(),
                         is_class<typename remove_reference<_Fn>::type>::value ||
                         is_function<typename remove_reference<_Fn>::type>::value,
                         is_member_pointer<typename remove_reference<_Fn>::type>::value
                        >
{
};

template <class _Fn, class _A0>
class _LIBCPP_VISIBLE result_of<_Fn(_A0)>
    : public __result_of<_Fn(_A0),
                         is_class<typename remove_reference<_Fn>::type>::value ||
                         is_function<typename remove_reference<_Fn>::type>::value,
                         is_member_pointer<typename remove_reference<_Fn>::type>::value
                        >
{
};

template <class _Fn, class _A0, class _A1>
class _LIBCPP_VISIBLE result_of<_Fn(_A0, _A1)>
    : public __result_of<_Fn(_A0, _A1),
                         is_class<typename remove_reference<_Fn>::type>::value ||
                         is_function<typename remove_reference<_Fn>::type>::value,
                         is_member_pointer<typename remove_reference<_Fn>::type>::value
                        >
{
};

template <class _Fn, class _A0, class _A1, class _A2>
class _LIBCPP_VISIBLE result_of<_Fn(_A0, _A1, _A2)>
    : public __result_of<_Fn(_A0, _A1, _A2),
                         is_class<typename remove_reference<_Fn>::type>::value ||
                         is_function<typename remove_reference<_Fn>::type>::value,
                         is_member_pointer<typename remove_reference<_Fn>::type>::value
                        >
{
};

#endif  // _LIBCPP_HAS_NO_VARIADICS

#ifndef _LIBCPP_HAS_NO_VARIADICS

// template <class T, class... Args> struct is_constructible;

//      main is_constructible test

template <class _Tp, class ..._Args>
decltype(_VSTD::move(_Tp(_VSTD::declval<_Args>()...)), true_type())
__is_constructible_test(_Tp&&, _Args&& ...);

template <class ..._Args>
false_type
__is_constructible_test(__any, _Args&& ...);

template <bool, class _Tp, class... _Args>
struct __is_constructible // false, _Tp is not a scalar
    : public common_type
             <
                 decltype(__is_constructible_test(declval<_Tp>(), declval<_Args>()...))
             >::type
    {};

//      function types are not constructible

template <class _Rp, class... _A1, class... _A2>
struct __is_constructible<false, _Rp(_A1...), _A2...>
    : public false_type
    {};

//      handle scalars and reference types

//      Scalars are default constructible, references are not

template <class _Tp>
struct __is_constructible<true, _Tp>
    : public is_scalar<_Tp>
    {};

//      Scalars and references are constructible from one arg if that arg is
//          implicitly convertible to the scalar or reference.

template <class _Tp>
struct __is_constructible_ref
{
    true_type static __(_Tp);
    false_type static __(...);
};

template <class _Tp, class _A0>
struct __is_constructible<true, _Tp, _A0>
    : public common_type
             <
                 decltype(__is_constructible_ref<_Tp>::__(declval<_A0>()))
             >::type
    {};

//      Scalars and references are not constructible from multiple args.

template <class _Tp, class _A0, class ..._Args>
struct __is_constructible<true, _Tp, _A0, _Args...>
    : public false_type
    {};

//      Treat scalars and reference types separately

template <bool, class _Tp, class... _Args>
struct __is_constructible_void_check
    : public __is_constructible<is_scalar<_Tp>::value || is_reference<_Tp>::value,
                                _Tp, _Args...>
    {};

//      If any of T or Args is void, is_constructible should be false

template <class _Tp, class... _Args>
struct __is_constructible_void_check<true, _Tp, _Args...>
    : public false_type
    {};

template <class ..._Args> struct __contains_void;

template <> struct __contains_void<> : false_type {};

template <class _A0, class ..._Args>
struct __contains_void<_A0, _Args...>
{
    static const bool value = is_void<_A0>::value ||
                              __contains_void<_Args...>::value;
};

//      is_constructible entry point

template <class _Tp, class... _Args>
struct _LIBCPP_VISIBLE is_constructible
    : public __is_constructible_void_check<__contains_void<_Tp, _Args...>::value
                                        || is_abstract<_Tp>::value,
                                           _Tp, _Args...>
    {};

//      Array types are default constructible if their element type
//      is default constructible

template <class _Ap, size_t _Np>
struct __is_constructible<false, _Ap[_Np]>
    : public is_constructible<typename remove_all_extents<_Ap>::type>
    {};

//      Otherwise array types are not constructible by this syntax

template <class _Ap, size_t _Np, class ..._Args>
struct __is_constructible<false, _Ap[_Np], _Args...>
    : public false_type
    {};

//      Incomplete array types are not constructible

template <class _Ap, class ..._Args>
struct __is_constructible<false, _Ap[], _Args...>
    : public false_type
    {};

#else  // _LIBCPP_HAS_NO_VARIADICS

// template <class T> struct is_constructible0;

//      main is_constructible0 test

template <class _Tp>
decltype((_Tp(), true_type()))
__is_constructible0_test(_Tp&);

false_type
__is_constructible0_test(__any);

template <class _Tp, class _A0>
decltype((_Tp(_VSTD::declval<_A0>()), true_type()))
__is_constructible1_test(_Tp&, _A0&);

template <class _A0>
false_type
__is_constructible1_test(__any, _A0&);

template <class _Tp, class _A0, class _A1>
decltype((_Tp(_VSTD::declval<_A0>(), _VSTD::declval<_A1>()), true_type()))
__is_constructible2_test(_Tp&, _A0&, _A1&);

template <class _A0, class _A1>
false_type
__is_constructible2_test(__any, _A0&, _A1&);

template <bool, class _Tp>
struct __is_constructible0_imp // false, _Tp is not a scalar
    : public common_type
             <
                 decltype(__is_constructible0_test(declval<_Tp&>()))
             >::type
    {};

template <bool, class _Tp, class _A0>
struct __is_constructible1_imp // false, _Tp is not a scalar
    : public common_type
             <
                 decltype(__is_constructible1_test(declval<_Tp&>(), declval<_A0&>()))
             >::type
    {};

template <bool, class _Tp, class _A0, class _A1>
struct __is_constructible2_imp // false, _Tp is not a scalar
    : public common_type
             <
                 decltype(__is_constructible2_test(declval<_Tp&>(), declval<_A0>(), declval<_A1>()))
             >::type
    {};

//      handle scalars and reference types

//      Scalars are default constructible, references are not

template <class _Tp>
struct __is_constructible0_imp<true, _Tp>
    : public is_scalar<_Tp>
    {};

template <class _Tp, class _A0>
struct __is_constructible1_imp<true, _Tp, _A0>
    : public is_convertible<_A0, _Tp>
    {};

template <class _Tp, class _A0, class _A1>
struct __is_constructible2_imp<true, _Tp, _A0, _A1>
    : public false_type
    {};

//      Treat scalars and reference types separately

template <bool, class _Tp>
struct __is_constructible0_void_check
    : public __is_constructible0_imp<is_scalar<_Tp>::value || is_reference<_Tp>::value,
                                _Tp>
    {};

template <bool, class _Tp, class _A0>
struct __is_constructible1_void_check
    : public __is_constructible1_imp<is_scalar<_Tp>::value || is_reference<_Tp>::value,
                                _Tp, _A0>
    {};

template <bool, class _Tp, class _A0, class _A1>
struct __is_constructible2_void_check
    : public __is_constructible2_imp<is_scalar<_Tp>::value || is_reference<_Tp>::value,
                                _Tp, _A0, _A1>
    {};

//      If any of T or Args is void, is_constructible should be false

template <class _Tp>
struct __is_constructible0_void_check<true, _Tp>
    : public false_type
    {};

template <class _Tp, class _A0>
struct __is_constructible1_void_check<true, _Tp, _A0>
    : public false_type
    {};

template <class _Tp, class _A0, class _A1>
struct __is_constructible2_void_check<true, _Tp, _A0, _A1>
    : public false_type
    {};

//      is_constructible entry point

namespace __is_construct
{

struct __nat {};

}

template <class _Tp, class _A0 = __is_construct::__nat,
                     class _A1 = __is_construct::__nat>
struct _LIBCPP_VISIBLE is_constructible
    : public __is_constructible2_void_check<is_void<_Tp>::value
                                        || is_abstract<_Tp>::value
                                        || is_function<_Tp>::value
                                        || is_void<_A0>::value
                                        || is_void<_A1>::value,
                                           _Tp, _A0, _A1>
    {};

template <class _Tp>
struct _LIBCPP_VISIBLE is_constructible<_Tp, __is_construct::__nat, __is_construct::__nat>
    : public __is_constructible0_void_check<is_void<_Tp>::value
                                        || is_abstract<_Tp>::value
                                        || is_function<_Tp>::value,
                                           _Tp>
    {};

template <class _Tp, class _A0>
struct _LIBCPP_VISIBLE is_constructible<_Tp, _A0, __is_construct::__nat>
    : public __is_constructible1_void_check<is_void<_Tp>::value
                                        || is_abstract<_Tp>::value
                                        || is_function<_Tp>::value
                                        || is_void<_A0>::value,
                                           _Tp, _A0>
    {};

//      Array types are default constructible if their element type
//      is default constructible

template <class _Ap, size_t _Np>
struct __is_constructible0_imp<false, _Ap[_Np]>
    : public is_constructible<typename remove_all_extents<_Ap>::type>
    {};

template <class _Ap, size_t _Np, class _A0>
struct __is_constructible1_imp<false, _Ap[_Np], _A0>
    : public false_type
    {};

template <class _Ap, size_t _Np, class _A0, class _A1>
struct __is_constructible2_imp<false, _Ap[_Np], _A0, _A1>
    : public false_type
    {};

//      Incomplete array types are not constructible

template <class _Ap>
struct __is_constructible0_imp<false, _Ap[]>
    : public false_type
    {};

template <class _Ap, class _A0>
struct __is_constructible1_imp<false, _Ap[], _A0>
    : public false_type
    {};

template <class _Ap, class _A0, class _A1>
struct __is_constructible2_imp<false, _Ap[], _A0, _A1>
    : public false_type
    {};

#endif  // _LIBCPP_HAS_NO_VARIADICS

// is_default_constructible

template <class _Tp>
struct _LIBCPP_VISIBLE is_default_constructible
    : public is_constructible<_Tp>
    {};

// is_copy_constructible

template <class _Tp>
struct _LIBCPP_VISIBLE is_copy_constructible
    : public is_constructible<_Tp, const typename add_lvalue_reference<_Tp>::type>
    {};

// is_move_constructible

template <class _Tp>
struct _LIBCPP_VISIBLE is_move_constructible
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
    : public is_constructible<_Tp, typename add_rvalue_reference<_Tp>::type>
#else
    : public is_copy_constructible<_Tp>
#endif
    {};

// is_trivially_constructible

#ifndef _LIBCPP_HAS_NO_VARIADICS

#if __has_feature(is_trivially_constructible)

template <class _Tp, class... _Args>
struct _LIBCPP_VISIBLE is_trivially_constructible
    : integral_constant<bool, __is_trivially_constructible(_Tp, _Args...)>
{
};

#else  // !__has_feature(is_trivially_constructible)

template <class _Tp, class... _Args>
struct _LIBCPP_VISIBLE is_trivially_constructible
    : false_type
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_trivially_constructible<_Tp>
#if __has_feature(has_trivial_constructor) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
    : integral_constant<bool, __has_trivial_constructor(_Tp)>
#else
    : integral_constant<bool, is_scalar<_Tp>::value>
#endif
{
};

template <class _Tp>
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
struct _LIBCPP_VISIBLE is_trivially_constructible<_Tp, _Tp&&>
#else
struct _LIBCPP_VISIBLE is_trivially_constructible<_Tp, _Tp>
#endif
    : integral_constant<bool, is_scalar<_Tp>::value>
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_trivially_constructible<_Tp, const _Tp&>
    : integral_constant<bool, is_scalar<_Tp>::value>
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_trivially_constructible<_Tp, _Tp&>
    : integral_constant<bool, is_scalar<_Tp>::value>
{
};

#endif  // !__has_feature(is_trivially_constructible)

#else  // _LIBCPP_HAS_NO_VARIADICS

template <class _Tp, class _A0 = __is_construct::__nat,
                     class _A1 = __is_construct::__nat>
struct _LIBCPP_VISIBLE is_trivially_constructible
    : false_type
{
};

#if __has_feature(is_trivially_constructible)

template <class _Tp>
struct _LIBCPP_VISIBLE is_trivially_constructible<_Tp, __is_construct::__nat,
                                                       __is_construct::__nat>
    : integral_constant<bool, __is_trivially_constructible(_Tp)>
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_trivially_constructible<_Tp, _Tp,
                                                       __is_construct::__nat>
    : integral_constant<bool, __is_trivially_constructible(_Tp, _Tp)>
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_trivially_constructible<_Tp, const _Tp&,
                                                       __is_construct::__nat>
    : integral_constant<bool, __is_trivially_constructible(_Tp, const _Tp&)>
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_trivially_constructible<_Tp, _Tp&,
                                                       __is_construct::__nat>
    : integral_constant<bool, __is_trivially_constructible(_Tp, _Tp&)>
{
};

#else  // !__has_feature(is_trivially_constructible)

template <class _Tp>
struct _LIBCPP_VISIBLE is_trivially_constructible<_Tp, __is_construct::__nat,
                                                       __is_construct::__nat>
    : integral_constant<bool, is_scalar<_Tp>::value>
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_trivially_constructible<_Tp, _Tp,
                                                       __is_construct::__nat>
    : integral_constant<bool, is_scalar<_Tp>::value>
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_trivially_constructible<_Tp, const _Tp&,
                                                       __is_construct::__nat>
    : integral_constant<bool, is_scalar<_Tp>::value>
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_trivially_constructible<_Tp, _Tp&,
                                                       __is_construct::__nat>
    : integral_constant<bool, is_scalar<_Tp>::value>
{
};

#endif  // !__has_feature(is_trivially_constructible)

#endif  // _LIBCPP_HAS_NO_VARIADICS

// is_trivially_default_constructible

template <class _Tp> struct _LIBCPP_VISIBLE is_trivially_default_constructible
    : public is_trivially_constructible<_Tp>
    {};

// is_trivially_copy_constructible

template <class _Tp> struct _LIBCPP_VISIBLE is_trivially_copy_constructible
    : public is_trivially_constructible<_Tp, const typename add_lvalue_reference<_Tp>::type>
    {};

// is_trivially_move_constructible

template <class _Tp> struct _LIBCPP_VISIBLE is_trivially_move_constructible
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
    : public is_trivially_constructible<_Tp, typename add_rvalue_reference<_Tp>::type>
#else
    : public is_trivially_copy_constructible<_Tp>
#endif
    {};

// is_trivially_assignable

#if __has_feature(is_trivially_constructible)

template <class _Tp, class _Arg>
struct is_trivially_assignable
    : integral_constant<bool, __is_trivially_assignable(_Tp, _Arg)>
{
};

#else  // !__has_feature(is_trivially_constructible)

template <class _Tp, class _Arg>
struct is_trivially_assignable
    : public false_type {};

template <class _Tp>
struct is_trivially_assignable<_Tp&, _Tp>
    : integral_constant<bool, is_scalar<_Tp>::value> {};

template <class _Tp>
struct is_trivially_assignable<_Tp&, _Tp&>
    : integral_constant<bool, is_scalar<_Tp>::value> {};

template <class _Tp>
struct is_trivially_assignable<_Tp&, const _Tp&>
    : integral_constant<bool, is_scalar<_Tp>::value> {};

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Tp>
struct is_trivially_assignable<_Tp&, _Tp&&>
    : integral_constant<bool, is_scalar<_Tp>::value> {};

#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES

#endif  // !__has_feature(is_trivially_constructible)

// is_trivially_copy_assignable

template <class _Tp> struct _LIBCPP_VISIBLE is_trivially_copy_assignable
    : public is_trivially_assignable<typename add_lvalue_reference<_Tp>::type,
                               const typename add_lvalue_reference<_Tp>::type>
    {};

// is_trivially_move_assignable

template <class _Tp> struct _LIBCPP_VISIBLE is_trivially_move_assignable
    : public is_trivially_assignable<typename add_lvalue_reference<_Tp>::type,
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
                                     typename add_rvalue_reference<_Tp>::type>
#else
                                     typename add_lvalue_reference<_Tp>::type>
#endif
    {};

// is_trivially_destructible

#if __has_feature(has_trivial_destructor) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)

template <class _Tp> struct _LIBCPP_VISIBLE is_trivially_destructible
    : public integral_constant<bool, __has_trivial_destructor(_Tp)> {};

#else  // _LIBCPP_HAS_TYPE_TRAITS

template <class _Tp> struct __libcpp_trivial_destructor
    : public integral_constant<bool, is_scalar<_Tp>::value ||
                                     is_reference<_Tp>::value> {};

template <class _Tp> struct _LIBCPP_VISIBLE is_trivially_destructible
    : public __libcpp_trivial_destructor<typename remove_all_extents<_Tp>::type> {};

#endif  // _LIBCPP_HAS_TYPE_TRAITS

// is_nothrow_constructible

#ifndef _LIBCPP_HAS_NO_VARIADICS

#if __has_feature(cxx_noexcept)

template <bool, class _Tp, class... _Args> struct __is_nothrow_constructible;

template <class _Tp, class... _Args>
struct __is_nothrow_constructible<true, _Tp, _Args...>
    : public integral_constant<bool, noexcept(_Tp(declval<_Args>()...))>
{
};

template <class _Tp, class... _Args>
struct __is_nothrow_constructible<false, _Tp, _Args...>
    : public false_type
{
};

template <class _Tp, class... _Args>
struct _LIBCPP_VISIBLE is_nothrow_constructible
    : __is_nothrow_constructible<is_constructible<_Tp, _Args...>::value, _Tp, _Args...>
{
};

template <class _Tp, size_t _Ns>
struct _LIBCPP_VISIBLE is_nothrow_constructible<_Tp[_Ns]>
    : __is_nothrow_constructible<is_constructible<_Tp>::value, _Tp>
{
};

#else  // __has_feature(cxx_noexcept)

template <class _Tp, class... _Args>
struct _LIBCPP_VISIBLE is_nothrow_constructible
    : false_type
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_nothrow_constructible<_Tp>
#if __has_feature(has_nothrow_constructor) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
    : integral_constant<bool, __has_nothrow_constructor(_Tp)>
#else
    : integral_constant<bool, is_scalar<_Tp>::value>
#endif
{
};

template <class _Tp>
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
struct _LIBCPP_VISIBLE is_nothrow_constructible<_Tp, _Tp&&>
#else
struct _LIBCPP_VISIBLE is_nothrow_constructible<_Tp, _Tp>
#endif
#if __has_feature(has_nothrow_copy) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
    : integral_constant<bool, __has_nothrow_copy(_Tp)>
#else
    : integral_constant<bool, is_scalar<_Tp>::value>
#endif
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_nothrow_constructible<_Tp, const _Tp&>
#if __has_feature(has_nothrow_copy) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
    : integral_constant<bool, __has_nothrow_copy(_Tp)>
#else
    : integral_constant<bool, is_scalar<_Tp>::value>
#endif
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_nothrow_constructible<_Tp, _Tp&>
#if __has_feature(has_nothrow_copy) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
    : integral_constant<bool, __has_nothrow_copy(_Tp)>
#else
    : integral_constant<bool, is_scalar<_Tp>::value>
#endif
{
};

#endif  // __has_feature(cxx_noexcept)

#else  // _LIBCPP_HAS_NO_VARIADICS

template <class _Tp, class _A0 = __is_construct::__nat,
                     class _A1 = __is_construct::__nat>
struct _LIBCPP_VISIBLE is_nothrow_constructible
    : false_type
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_nothrow_constructible<_Tp, __is_construct::__nat,
                                                       __is_construct::__nat>
#if __has_feature(has_nothrow_constructor) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
    : integral_constant<bool, __has_nothrow_constructor(_Tp)>
#else
    : integral_constant<bool, is_scalar<_Tp>::value>
#endif
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_nothrow_constructible<_Tp, _Tp,
                                                       __is_construct::__nat>
#if __has_feature(has_nothrow_copy) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
    : integral_constant<bool, __has_nothrow_copy(_Tp)>
#else
    : integral_constant<bool, is_scalar<_Tp>::value>
#endif
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_nothrow_constructible<_Tp, const _Tp&,
                                                       __is_construct::__nat>
#if __has_feature(has_nothrow_copy) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
    : integral_constant<bool, __has_nothrow_copy(_Tp)>
#else
    : integral_constant<bool, is_scalar<_Tp>::value>
#endif
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_nothrow_constructible<_Tp, _Tp&,
                                                       __is_construct::__nat>
#if __has_feature(has_nothrow_copy) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
    : integral_constant<bool, __has_nothrow_copy(_Tp)>
#else
    : integral_constant<bool, is_scalar<_Tp>::value>
#endif
{
};

#endif  // _LIBCPP_HAS_NO_VARIADICS

// is_nothrow_default_constructible

template <class _Tp> struct _LIBCPP_VISIBLE is_nothrow_default_constructible
    : public is_nothrow_constructible<_Tp>
    {};

// is_nothrow_copy_constructible

template <class _Tp> struct _LIBCPP_VISIBLE is_nothrow_copy_constructible
    : public is_nothrow_constructible<_Tp, const typename add_lvalue_reference<_Tp>::type>
    {};

// is_nothrow_move_constructible

template <class _Tp> struct _LIBCPP_VISIBLE is_nothrow_move_constructible
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
    : public is_nothrow_constructible<_Tp, typename add_rvalue_reference<_Tp>::type>
#else
    : public is_nothrow_copy_constructible<_Tp>
#endif
    {};

// is_nothrow_assignable

#if __has_feature(cxx_noexcept)

template <bool, class _Tp, class _Arg> struct __is_nothrow_assignable;

template <class _Tp, class _Arg>
struct __is_nothrow_assignable<false, _Tp, _Arg>
    : public false_type
{
};

template <class _Tp, class _Arg>
struct __is_nothrow_assignable<true, _Tp, _Arg>
    : public integral_constant<bool, noexcept(_VSTD::declval<_Tp>() = _VSTD::declval<_Arg>()) >
{
};

template <class _Tp, class _Arg>
struct _LIBCPP_VISIBLE is_nothrow_assignable
    : public __is_nothrow_assignable<is_assignable<_Tp, _Arg>::value, _Tp, _Arg>
{
};

#else  // __has_feature(cxx_noexcept)

template <class _Tp, class _Arg>
struct _LIBCPP_VISIBLE is_nothrow_assignable
    : public false_type {};

template <class _Tp>
struct _LIBCPP_VISIBLE is_nothrow_assignable<_Tp&, _Tp>
#if __has_feature(has_nothrow_assign) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
    : integral_constant<bool, __has_nothrow_assign(_Tp)> {};
#else
    : integral_constant<bool, is_scalar<_Tp>::value> {};
#endif

template <class _Tp>
struct _LIBCPP_VISIBLE is_nothrow_assignable<_Tp&, _Tp&>
#if __has_feature(has_nothrow_assign) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
    : integral_constant<bool, __has_nothrow_assign(_Tp)> {};
#else
    : integral_constant<bool, is_scalar<_Tp>::value> {};
#endif

template <class _Tp>
struct _LIBCPP_VISIBLE is_nothrow_assignable<_Tp&, const _Tp&>
#if __has_feature(has_nothrow_assign) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
    : integral_constant<bool, __has_nothrow_assign(_Tp)> {};
#else
    : integral_constant<bool, is_scalar<_Tp>::value> {};
#endif

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Tp>
struct is_nothrow_assignable<_Tp&, _Tp&&>
#if __has_feature(has_nothrow_assign) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)
    : integral_constant<bool, __has_nothrow_assign(_Tp)> {};
#else
    : integral_constant<bool, is_scalar<_Tp>::value> {};
#endif

#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES

#endif  // __has_feature(cxx_noexcept)

// is_nothrow_copy_assignable

template <class _Tp> struct _LIBCPP_VISIBLE is_nothrow_copy_assignable
    : public is_nothrow_assignable<typename add_lvalue_reference<_Tp>::type,
                               const typename add_lvalue_reference<_Tp>::type>
    {};

// is_nothrow_move_assignable

template <class _Tp> struct _LIBCPP_VISIBLE is_nothrow_move_assignable
    : public is_nothrow_assignable<typename add_lvalue_reference<_Tp>::type,
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
                                     typename add_rvalue_reference<_Tp>::type>
#else
                                     typename add_lvalue_reference<_Tp>::type>
#endif
    {};

// is_nothrow_destructible

#if __has_feature(cxx_noexcept)

template <bool, class _Tp> struct __is_nothrow_destructible;

template <class _Tp>
struct __is_nothrow_destructible<false, _Tp>
    : public false_type
{
};

template <class _Tp>
struct __is_nothrow_destructible<true, _Tp>
    : public integral_constant<bool, noexcept(_VSTD::declval<_Tp>().~_Tp()) >
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_nothrow_destructible
    : public __is_nothrow_destructible<is_destructible<_Tp>::value, _Tp>
{
};

template <class _Tp, size_t _Ns>
struct _LIBCPP_VISIBLE is_nothrow_destructible<_Tp[_Ns]>
    : public is_nothrow_destructible<_Tp>
{
};

template <class _Tp>
struct _LIBCPP_VISIBLE is_nothrow_destructible<_Tp&>
    : public true_type
{
};

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Tp>
struct _LIBCPP_VISIBLE is_nothrow_destructible<_Tp&&>
    : public true_type
{
};

#endif

#else

template <class _Tp> struct __libcpp_nothrow_destructor
    : public integral_constant<bool, is_scalar<_Tp>::value ||
                                     is_reference<_Tp>::value> {};

template <class _Tp> struct _LIBCPP_VISIBLE is_nothrow_destructible
    : public __libcpp_nothrow_destructor<typename remove_all_extents<_Tp>::type> {};

#endif

// is_pod

#if __has_feature(is_pod) || (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)

template <class _Tp> struct _LIBCPP_VISIBLE is_pod
    : public integral_constant<bool, __is_pod(_Tp)> {};

#else  // _LIBCPP_HAS_TYPE_TRAITS

template <class _Tp> struct _LIBCPP_VISIBLE is_pod
    : public integral_constant<bool, is_trivially_default_constructible<_Tp>::value   &&
                                     is_trivially_copy_constructible<_Tp>::value      &&
                                     is_trivially_copy_assignable<_Tp>::value    &&
                                     is_trivially_destructible<_Tp>::value> {};

#endif  // _LIBCPP_HAS_TYPE_TRAITS

// is_literal_type;

template <class _Tp> struct _LIBCPP_VISIBLE is_literal_type
#if __has_feature(is_literal)
    : public integral_constant<bool, __is_literal(_Tp)>
#else
    : integral_constant<bool, is_scalar<typename remove_all_extents<_Tp>::type>::value ||
                              is_reference<typename remove_all_extents<_Tp>::type>::value>
#endif
    {};
    
// is_standard_layout;

template <class _Tp> struct _LIBCPP_VISIBLE is_standard_layout
#if __has_feature(is_standard_layout)
    : public integral_constant<bool, __is_standard_layout(_Tp)>
#else
    : integral_constant<bool, is_scalar<typename remove_all_extents<_Tp>::type>::value>
#endif
    {};
    
// is_trivially_copyable;

template <class _Tp> struct _LIBCPP_VISIBLE is_trivially_copyable
#if __has_feature(is_trivially_copyable)
    : public integral_constant<bool, __is_trivially_copyable(_Tp)>
#else
    : integral_constant<bool, is_scalar<typename remove_all_extents<_Tp>::type>::value>
#endif
    {};
    
// is_trivial;

template <class _Tp> struct _LIBCPP_VISIBLE is_trivial
#if __has_feature(is_trivial)
    : public integral_constant<bool, __is_trivial(_Tp)>
#else
    : integral_constant<bool, is_trivially_copyable<_Tp>::value &&
                                 is_trivially_default_constructible<_Tp>::value>
#endif
    {};

#ifndef _LIBCPP_HAS_NO_VARIADICS

// Check for complete types

template <class ..._Tp> struct __check_complete;

template <>
struct __check_complete<>
{
};

template <class _Hp, class _T0, class ..._Tp>
struct __check_complete<_Hp, _T0, _Tp...>
    : private __check_complete<_Hp>,
      private __check_complete<_T0, _Tp...>
{
};

template <class _Hp>
struct __check_complete<_Hp, _Hp>
    : private __check_complete<_Hp>
{
};

template <class _Tp>
struct __check_complete<_Tp>
{
    static_assert(sizeof(_Tp) > 0, "Type must be complete.");
};

template <class _Tp>
struct __check_complete<_Tp&>
    : private __check_complete<_Tp>
{
};

template <class _Tp>
struct __check_complete<_Tp&&>
    : private __check_complete<_Tp>
{
};

template <class _Rp, class ..._Param>
struct __check_complete<_Rp (*)(_Param...)>
    : private __check_complete<_Param...>
{
};

template <class _Rp, class ..._Param>
struct __check_complete<_Rp (_Param...)>
    : private __check_complete<_Param...>
{
};

template <class _Rp, class _Class, class ..._Param>
struct __check_complete<_Rp (_Class::*)(_Param...)>
    : private __check_complete<_Class, _Param...>
{
};

template <class _Rp, class _Class, class ..._Param>
struct __check_complete<_Rp (_Class::*)(_Param...) const>
    : private __check_complete<_Class, _Param...>
{
};

template <class _Rp, class _Class, class ..._Param>
struct __check_complete<_Rp (_Class::*)(_Param...) volatile>
    : private __check_complete<_Class, _Param...>
{
};

template <class _Rp, class _Class, class ..._Param>
struct __check_complete<_Rp (_Class::*)(_Param...) const volatile>
    : private __check_complete<_Class, _Param...>
{
};

#if __has_feature(cxx_reference_qualified_functions)

template <class _Rp, class _Class, class ..._Param>
struct __check_complete<_Rp (_Class::*)(_Param...) &>
    : private __check_complete<_Class, _Param...>
{
};

template <class _Rp, class _Class, class ..._Param>
struct __check_complete<_Rp (_Class::*)(_Param...) const&>
    : private __check_complete<_Class, _Param...>
{
};

template <class _Rp, class _Class, class ..._Param>
struct __check_complete<_Rp (_Class::*)(_Param...) volatile&>
    : private __check_complete<_Class, _Param...>
{
};

template <class _Rp, class _Class, class ..._Param>
struct __check_complete<_Rp (_Class::*)(_Param...) const volatile&>
    : private __check_complete<_Class, _Param...>
{
};

template <class _Rp, class _Class, class ..._Param>
struct __check_complete<_Rp (_Class::*)(_Param...) &&>
    : private __check_complete<_Class, _Param...>
{
};

template <class _Rp, class _Class, class ..._Param>
struct __check_complete<_Rp (_Class::*)(_Param...) const&&>
    : private __check_complete<_Class, _Param...>
{
};

template <class _Rp, class _Class, class ..._Param>
struct __check_complete<_Rp (_Class::*)(_Param...) volatile&&>
    : private __check_complete<_Class, _Param...>
{
};

template <class _Rp, class _Class, class ..._Param>
struct __check_complete<_Rp (_Class::*)(_Param...) const volatile&&>
    : private __check_complete<_Class, _Param...>
{
};

#endif

template <class _Rp, class _Class>
struct __check_complete<_Rp _Class::*>
    : private __check_complete<_Class>
{
};

// __invoke forward declarations

// fall back - none of the bullets

template <class ..._Args>
auto
__invoke(__any, _Args&& ...__args)
    -> __nat;

// bullets 1 and 2

template <class _Fp, class _A0, class ..._Args>
auto
__invoke(_Fp&& __f, _A0&& __a0, _Args&& ...__args)
    -> decltype((_VSTD::forward<_A0>(__a0).*__f)(_VSTD::forward<_Args>(__args)...));

template <class _Fp, class _A0, class ..._Args>
auto
__invoke(_Fp&& __f, _A0&& __a0, _Args&& ...__args)
    -> decltype(((*_VSTD::forward<_A0>(__a0)).*__f)(_VSTD::forward<_Args>(__args)...));

// bullets 3 and 4

template <class _Fp, class _A0>
auto
__invoke(_Fp&& __f, _A0&& __a0)
    -> decltype(_VSTD::forward<_A0>(__a0).*__f);

template <class _Fp, class _A0>
auto
__invoke(_Fp&& __f, _A0&& __a0)
    -> decltype((*_VSTD::forward<_A0>(__a0)).*__f);

// bullet 5

template <class _Fp, class ..._Args>
auto
__invoke(_Fp&& __f, _Args&& ...__args)
    -> decltype(_VSTD::forward<_Fp>(__f)(_VSTD::forward<_Args>(__args)...));

// __invokable

template <class _Fp, class ..._Args>
struct __invokable_imp
    : private __check_complete<_Fp, _Args...>
{
    typedef decltype(
            __invoke(_VSTD::declval<_Fp>(), _VSTD::declval<_Args>()...)
                    ) type;
    static const bool value = !is_same<type, __nat>::value;
};

template <class _Fp, class ..._Args>
struct __invokable
    : public integral_constant<bool,
          __invokable_imp<_Fp, _Args...>::value>
{
};

// __invoke_of

template <bool _Invokable, class _Fp, class ..._Args>
struct __invoke_of_imp  // false
{
};

template <class _Fp, class ..._Args>
struct __invoke_of_imp<true, _Fp, _Args...>
{
    typedef typename __invokable_imp<_Fp, _Args...>::type type;
};

template <class _Fp, class ..._Args>
struct __invoke_of
    : public __invoke_of_imp<__invokable<_Fp, _Args...>::value, _Fp, _Args...>
{
};

#endif  // _LIBCPP_HAS_NO_VARIADICS

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
#ifndef _LIBCPP_HAS_NO_ADVANCED_SFINAE
typename enable_if
<
    is_move_constructible<_Tp>::value &&
    is_move_assignable<_Tp>::value
>::type
#else
void
#endif
swap(_Tp& __x, _Tp& __y) _NOEXCEPT_(is_nothrow_move_constructible<_Tp>::value &&
                                    is_nothrow_move_assignable<_Tp>::value)
{
    _Tp __t(_VSTD::move(__x));
    __x = _VSTD::move(__y);
    __y = _VSTD::move(__t);
}

template <class _ForwardIterator1, class _ForwardIterator2>
inline _LIBCPP_INLINE_VISIBILITY
void
iter_swap(_ForwardIterator1 __a, _ForwardIterator2 __b)
    //                                  _NOEXCEPT_(_NOEXCEPT_(swap(*__a, *__b)))
               _NOEXCEPT_(_NOEXCEPT_(swap(*_VSTD::declval<_ForwardIterator1>(),
                                          *_VSTD::declval<_ForwardIterator2>())))
{
    swap(*__a, *__b);
}

// __swappable

namespace __detail
{

using _VSTD::swap;
__nat swap(__any, __any);

template <class _Tp>
struct __swappable
{
    typedef decltype(swap(_VSTD::declval<_Tp&>(), _VSTD::declval<_Tp&>())) type;
    static const bool value = !is_same<type, __nat>::value;
};

}  // __detail

template <class _Tp>
struct __is_swappable
    : public integral_constant<bool, __detail::__swappable<_Tp>::value>
{
};

#if __has_feature(cxx_noexcept)

template <bool, class _Tp>
struct __is_nothrow_swappable_imp
    : public integral_constant<bool, noexcept(swap(_VSTD::declval<_Tp&>(),
                                                   _VSTD::declval<_Tp&>()))>
{
};

template <class _Tp>
struct __is_nothrow_swappable_imp<false, _Tp>
    : public false_type
{
};

template <class _Tp>
struct __is_nothrow_swappable
    : public __is_nothrow_swappable_imp<__is_swappable<_Tp>::value, _Tp>
{
};

#else  // __has_feature(cxx_noexcept)

template <class _Tp>
struct __is_nothrow_swappable
    : public false_type
{
};

#endif  // __has_feature(cxx_noexcept)

#ifdef _LIBCXX_UNDERLYING_TYPE

template <class _Tp>
struct underlying_type
{
    typedef _LIBCXX_UNDERLYING_TYPE(_Tp) type;
};

#else  // _LIBCXX_UNDERLYING_TYPE

template <class _Tp, bool _Support = false>
struct underlying_type
{
    static_assert(_Support, "The underyling_type trait requires compiler "
                            "support. Either no such support exists or "
                            "libc++ does not know how to use it.");
};

#endif // _LIBCXX_UNDERLYING_TYPE

_LIBCPP_END_NAMESPACE_STD

#endif  // _LIBCPP_TYPE_TRAITS