// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
//                     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_FUNCTIONAL_BASE_03
#define _LIBCPP_FUNCTIONAL_BASE_03

// manual variadic expansion for <functional>

// __weak_result_type

template <class _Tp>
struct __derives_from_unary_function
{
private:
    struct __two {char _; char __;};
    static __two __test(...);
    template <class _A, class _R>
        static unary_function<_A, _R>
        __test(const volatile unary_function<_A, _R>*);
public:
    static const bool value = !is_same<decltype(__test((_Tp*)0)), __two>::value;
    typedef decltype(__test((_Tp*)0)) type;
};

template <class _Tp>
struct __derives_from_binary_function
{
private:
    struct __two {char _; char __;};
    static __two __test(...);
    template <class _A1, class _A2, class _R>
        static binary_function<_A1, _A2, _R>
        __test(const volatile binary_function<_A1, _A2, _R>*);
public:
    static const bool value = !is_same<decltype(__test((_Tp*)0)), __two>::value;
    typedef decltype(__test((_Tp*)0)) type;
};

template <class _Tp, bool = __derives_from_unary_function<_Tp>::value>
struct __maybe_derive_from_unary_function  // bool is true
    : public __derives_from_unary_function<_Tp>::type
{
};

template <class _Tp>
struct __maybe_derive_from_unary_function<_Tp, false>
{
};

template <class _Tp, bool = __derives_from_binary_function<_Tp>::value>
struct __maybe_derive_from_binary_function  // bool is true
    : public __derives_from_binary_function<_Tp>::type
{
};

template <class _Tp>
struct __maybe_derive_from_binary_function<_Tp, false>
{
};

template <class _Tp, bool = __has_result_type<_Tp>::value>
struct __weak_result_type_imp // bool is true
    : public __maybe_derive_from_unary_function<_Tp>,
      public __maybe_derive_from_binary_function<_Tp>
{
    typedef typename _Tp::result_type result_type;
};

template <class _Tp>
struct __weak_result_type_imp<_Tp, false>
    : public __maybe_derive_from_unary_function<_Tp>,
      public __maybe_derive_from_binary_function<_Tp>
{
};

template <class _Tp>
struct __weak_result_type
    : public __weak_result_type_imp<typename remove_reference<_Tp>::type>
{
};

// 0 argument case

template <class _R>
struct __weak_result_type<_R ()>
{
    typedef _R result_type;
};

template <class _R>
struct __weak_result_type<_R (&)()>
{
    typedef _R result_type;
};

template <class _R>
struct __weak_result_type<_R (*)()>
{
    typedef _R result_type;
};

// 1 argument case

template <class _R, class _A1>
struct __weak_result_type<_R (_A1)>
    : public unary_function<_A1, _R>
{
};

template <class _R, class _A1>
struct __weak_result_type<_R (&)(_A1)>
    : public unary_function<_A1, _R>
{
};

template <class _R, class _A1>
struct __weak_result_type<_R (*)(_A1)>
    : public unary_function<_A1, _R>
{
};

template <class _R, class _C>
struct __weak_result_type<_R (_C::*)()>
    : public unary_function<_C*, _R>
{
};

template <class _R, class _C>
struct __weak_result_type<_R (_C::*)() const>
    : public unary_function<const _C*, _R>
{
};

template <class _R, class _C>
struct __weak_result_type<_R (_C::*)() volatile>
    : public unary_function<volatile _C*, _R>
{
};

template <class _R, class _C>
struct __weak_result_type<_R (_C::*)() const volatile>
    : public unary_function<const volatile _C*, _R>
{
};

// 2 argument case

template <class _R, class _A1, class _A2>
struct __weak_result_type<_R (_A1, _A2)>
    : public binary_function<_A1, _A2, _R>
{
};

template <class _R, class _A1, class _A2>
struct __weak_result_type<_R (*)(_A1, _A2)>
    : public binary_function<_A1, _A2, _R>
{
};

template <class _R, class _A1, class _A2>
struct __weak_result_type<_R (&)(_A1, _A2)>
    : public binary_function<_A1, _A2, _R>
{
};

template <class _R, class _C, class _A1>
struct __weak_result_type<_R (_C::*)(_A1)>
    : public binary_function<_C*, _A1, _R>
{
};

template <class _R, class _C, class _A1>
struct __weak_result_type<_R (_C::*)(_A1) const>
    : public binary_function<const _C*, _A1, _R>
{
};

template <class _R, class _C, class _A1>
struct __weak_result_type<_R (_C::*)(_A1) volatile>
    : public binary_function<volatile _C*, _A1, _R>
{
};

template <class _R, class _C, class _A1>
struct __weak_result_type<_R (_C::*)(_A1) const volatile>
    : public binary_function<const volatile _C*, _A1, _R>
{
};

// 3 or more arguments

template <class _R, class _A1, class _A2, class _A3>
struct __weak_result_type<_R (_A1, _A2, _A3)>
{
    typedef _R result_type;
};

template <class _R, class _A1, class _A2, class _A3>
struct __weak_result_type<_R (&)(_A1, _A2, _A3)>
{
    typedef _R result_type;
};

template <class _R, class _A1, class _A2, class _A3>
struct __weak_result_type<_R (*)(_A1, _A2, _A3)>
{
    typedef _R result_type;
};

template <class _R, class _C, class _A1, class _A2>
struct __weak_result_type<_R (_C::*)(_A1, _A2)>
{
    typedef _R result_type;
};

template <class _R, class _C, class _A1, class _A2>
struct __weak_result_type<_R (_C::*)(_A1, _A2) const>
{
    typedef _R result_type;
};

template <class _R, class _C, class _A1, class _A2>
struct __weak_result_type<_R (_C::*)(_A1, _A2) volatile>
{
    typedef _R result_type;
};

// __invoke

// __ref_return0
//
// template <class _Tp, bool _HasResultType>
// struct ________ref_return0  // _HasResultType is true
// {
//     typedef typename _Tp::result_type type;
// };
//
// template <class _Tp>
// struct ________ref_return0<_Tp, false>
// {
//     typedef void type;
// };
//
// template <class _Tp, bool _IsClass>
// struct ____ref_return0  // _IsClass is true
//     : public ________ref_return0<_Tp, __has_result_type<typename remove_cv<_Tp>::type>::value>
// {
// };
//
// template <class _Tp, bool _HasResultType>
// struct ______ref_return0  // _HasResultType is true
// {
//     typedef typename __callable_type<_Tp>::result_type type;
// };
//
// template <class _Tp>
// struct ______ref_return0<_Tp, false>  // pointer to member data
// {
//     typedef void type;
// };
//
// template <class _Tp>
// struct ____ref_return0<_Tp, false>
//     : public ______ref_return0<typename remove_cv<_Tp>::type,
//                  __has_result_type<__callable_type<typename remove_cv<_Tp>::type> >::value>
// {
// };
//
// template <class _Tp>
// struct __ref_return0
//     : public ____ref_return0<typename remove_reference<_Tp>::type,
//                    is_class<typename remove_reference<_Tp>::type>::value>
// {
// };
//
// __ref_return1
//
// template <class _Tp, bool _IsClass, class _A0>
// struct ____ref_return1  // _IsClass is true
// {
//     typedef typename result_of<_Tp(_A0)>::type type;
// };
//
// template <class _Tp, bool _HasResultType, class _A0>
// struct ______ref_return1  // _HasResultType is true
// {
//     typedef typename __callable_type<_Tp>::result_type type;
// };
//
// template <class _Tp, class _A0, bool>
// struct __ref_return1_member_data1;
//
// template <class _R, class _C, class _A0>
// struct __ref_return1_member_data1<_R _C::*, _A0, true>
// {
//     typedef typename __apply_cv<_A0, _R>::type& type;
// };
//
// template <class _R, class _C, class _A0>
// struct __ref_return1_member_data1<_R _C::*, _A0, false>
// {
//     static _A0 __a;
//     typedef typename __apply_cv<decltype(*__a), _R>::type& type;
// };
//
// template <class _Tp, class _A0>
// struct __ref_return1_member_data;
//
// template <class _R, class _C, class _A0>
// struct __ref_return1_member_data<_R _C::*, _A0>
//     : public __ref_return1_member_data1<_R _C::*, _A0,
//                 is_same<typename remove_cv<_C>::type,
//                         typename remove_cv<typename remove_reference<_A0>::type>::type>::value>
// {
// };
//
// template <class _Tp, class _A0>
// struct ______ref_return1<_Tp, false, _A0>  // pointer to member data
//     : public __ref_return1_member_data<typename remove_cv<_Tp>::type, _A0>
// {
// };
//
// template <class _Tp, class _A0>
// struct ____ref_return1<_Tp, false, _A0>
//     : public ______ref_return1<typename remove_cv<_Tp>::type,
//                  __has_result_type<__callable_type<typename remove_cv<_Tp>::type> >::value, _A0>
// {
// };
//
// template <class _Tp, class _A0>
// struct __ref_return1
//     : public ____ref_return1<typename remove_reference<_Tp>::type,
//                    is_class<typename remove_reference<_Tp>::type>::value, _A0>
// {
// };
//
// __ref_return2
//
// template <class _Tp, bool _IsClass, class _A0, class _A1>
// struct ____ref_return2  // _IsClass is true
// {
//     typedef typename result_of<_Tp(_A0, _A1)>::type type;
// };
//
// template <class _Tp, bool _HasResultType, class _A0, class _A1>
// struct ______ref_return2  // _HasResultType is true
// {
//     typedef typename __callable_type<_Tp>::result_type type;
// };
//
// template <class _Tp>
// struct ______ref_return2<_Tp, false, class _A0, class _A1>  // pointer to member data
// {
//     static_assert(sizeof(_Tp) == 0, "An attempt has been made to `call` a pointer"
//                          " to member data with too many arguments.");
// };
//
// template <class _Tp, class _A0, class _A1>
// struct ____ref_return2<_Tp, false, _A0, _A1>
//     : public ______ref_return2<typename remove_cv<_Tp>::type,
//                  __has_result_type<__callable_type<typename remove_cv<_Tp>::type> >::value, _A0, _A1>
// {
// };
//
// template <class _Tp, class _A0, class _A1>
// struct __ref_return2
//     : public ____ref_return2<typename remove_reference<_Tp>::type,
//                    is_class<typename remove_reference<_Tp>::type>::value, _A0, _A1>
// {
// };
//
// __ref_return3
//
// template <class _Tp, bool _IsClass, class _A0, class _A1, class _A2>
// struct ____ref_return3  // _IsClass is true
// {
//     typedef typename result_of<_Tp(_A0, _A1, _A2)>::type type;
// };
//
// template <class _Tp, bool _HasResultType, class _A0, class _A1, class _A2>
// struct ______ref_return3  // _HasResultType is true
// {
//     typedef typename __callable_type<_Tp>::result_type type;
// };
//
// template <class _Tp>
// struct ______ref_return3<_Tp, false, class _A0, class _A1, class _A2>  // pointer to member data
// {
//     static_assert(sizeof(_Tp) == 0, "An attempt has been made to `call` a pointer"
//                          " to member data with too many arguments.");
// };
//
// template <class _Tp, class _A0, class _A1, class _A2>
// struct ____ref_return3<_Tp, false, _A0, _A1, _A2>
//     : public ______ref_return3<typename remove_cv<_Tp>::type,
//                  __has_result_type<__callable_type<typename remove_cv<_Tp>::type> >::value, _A0, _A1, _A2>
// {
// };
//
// template <class _Tp, class _A0, class _A1, class _A2>
// struct __ref_return3
//     : public ____ref_return3<typename remove_reference<_Tp>::type,
//                    is_class<typename remove_reference<_Tp>::type>::value, _A0, _A1, _A2>
// {
// };

// first bullet

template <class _R, class _T, class _T1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(), _T1& __t1)
{
    return (__t1.*__f)();
}

template <class _R, class _T, class _T1, class _A0>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0), _T1& __t1, _A0& __a0)
{
    return (__t1.*__f)(__a0);
}

template <class _R, class _T, class _T1, class _A0, class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1), _T1& __t1, _A0& __a0, _A1& __a1)
{
    return (__t1.*__f)(__a0, __a1);
}

template <class _R, class _T, class _T1, class _A0, class _A1, class _A2>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1, _A2), _T1& __t1, _A0& __a0, _A1& __a1, _A2& __a2)
{
    return (__t1.*__f)(__a0, __a1, __a2);
}

template <class _R, class _T, class _T1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)() const, _T1& __t1)
{
    return (__t1.*__f)();
}

template <class _R, class _T, class _T1, class _A0>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0) const, _T1& __t1, _A0& __a0)
{
    return (__t1.*__f)(__a0);
}

template <class _R, class _T, class _T1, class _A0, class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1) const, _T1& __t1, _A0& __a0, _A1& __a1)
{
    return (__t1.*__f)(__a0, __a1);
}

template <class _R, class _T, class _T1, class _A0, class _A1, class _A2>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1, _A2) const, _T1& __t1, _A0& __a0, _A1& __a1, _A2& __a2)
{
    return (__t1.*__f)(__a0, __a1, __a2);
}

template <class _R, class _T, class _T1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)() volatile, _T1& __t1)
{
    return (__t1.*__f)();
}

template <class _R, class _T, class _T1, class _A0>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0) volatile, _T1& __t1, _A0& __a0)
{
    return (__t1.*__f)(__a0);
}

template <class _R, class _T, class _T1, class _A0, class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1) volatile, _T1& __t1, _A0& __a0, _A1& __a1)
{
    return (__t1.*__f)(__a0, __a1);
}

template <class _R, class _T, class _T1, class _A0, class _A1, class _A2>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1, _A2) volatile, _T1& __t1, _A0& __a0, _A1& __a1, _A2& __a2)
{
    return (__t1.*__f)(__a0, __a1, __a2);
}

template <class _R, class _T, class _T1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)() const volatile, _T1& __t1)
{
    return (__t1.*__f)();
}

template <class _R, class _T, class _T1, class _A0>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0) const volatile, _T1& __t1, _A0& __a0)
{
    return (__t1.*__f)(__a0);
}

template <class _R, class _T, class _T1, class _A0, class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1) const volatile, _T1& __t1, _A0& __a0, _A1& __a1)
{
    return (__t1.*__f)(__a0, __a1);
}

template <class _R, class _T, class _T1, class _A0, class _A1, class _A2>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1, _A2) const volatile, _T1& __t1, _A0& __a0, _A1& __a1, _A2& __a2)
{
    return (__t1.*__f)(__a0, __a1, __a2);
}

// second bullet

template <class _R, class _T, class _T1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(), _T1 __t1)
{
    return ((*__t1).*__f)();
}

template <class _R, class _T, class _T1, class _A0>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0), _T1 __t1, _A0& __a0)
{
    return ((*__t1).*__f)(__a0);
}

template <class _R, class _T, class _T1, class _A0, class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1), _T1 __t1, _A0& __a0, _A1& __a1)
{
    return ((*__t1).*__f)(__a0, __a1);
}

template <class _R, class _T, class _T1, class _A0, class _A1, class _A2>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1, _A2), _T1 __t1, _A0& __a0, _A1& __a1, _A2& __a2)
{
    return ((*__t1).*__f)(__a0, __a1, __a2);
}

template <class _R, class _T, class _T1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)() const, _T1 __t1)
{
    return ((*__t1).*__f)();
}

template <class _R, class _T, class _T1, class _A0>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0) const, _T1 __t1, _A0& __a0)
{
    return ((*__t1).*__f)(__a0);
}

template <class _R, class _T, class _T1, class _A0, class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1) const, _T1 __t1, _A0& __a0, _A1& __a1)
{
    return ((*__t1).*__f)(__a0, __a1);
}

template <class _R, class _T, class _T1, class _A0, class _A1, class _A2>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1, _A2) const, _T1 __t1, _A0& __a0, _A1& __a1, _A2& __a2)
{
    return ((*__t1).*__f)(__a0, __a1, __a2);
}

template <class _R, class _T, class _T1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)() volatile, _T1 __t1)
{
    return ((*__t1).*__f)();
}

template <class _R, class _T, class _T1, class _A0>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0) volatile, _T1 __t1, _A0& __a0)
{
    return ((*__t1).*__f)(__a0);
}

template <class _R, class _T, class _T1, class _A0, class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1) volatile, _T1 __t1, _A0& __a0, _A1& __a1)
{
    return ((*__t1).*__f)(__a0, __a1);
}

template <class _R, class _T, class _T1, class _A0, class _A1, class _A2>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1, _A2) volatile, _T1 __t1, _A0& __a0, _A1& __a1, _A2& __a2)
{
    return ((*__t1).*__f)(__a0, __a1, __a2);
}

template <class _R, class _T, class _T1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)() const volatile, _T1 __t1)
{
    return ((*__t1).*__f)();
}

template <class _R, class _T, class _T1, class _A0>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0) const volatile, _T1 __t1, _A0& __a0)
{
    return ((*__t1).*__f)(__a0);
}

template <class _R, class _T, class _T1, class _A0, class _A1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1) const volatile, _T1 __t1, _A0& __a0, _A1& __a1)
{
    return ((*__t1).*__f)(__a0, __a1);
}

template <class _R, class _T, class _T1, class _A0, class _A1, class _A2>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    !is_base_of<_T, typename remove_reference<_T1>::type>::value,
    _R
>::type
__invoke(_R (_T::*__f)(_A0, _A1, _A2) const volatile, _T1 __t1, _A0& __a0, _A1& __a1, _A2& __a2)
{
    return ((*__t1).*__f)(__a0, __a1, __a2);
}

// third bullet

template <class _R, class _T, class _T1>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
    is_base_of<_T, typename remove_reference<_T1>::type>::value,
    typename __apply_cv<_T1, _R>::type&
>::type
__invoke(_R _T::* __f, _T1& __t1)
{
    return __t1.*__f;
}

template <class _R, class _T>
inline _LIBCPP_INLINE_VISIBILITY
void
__invoke(_R _T::*)
{
}

// template <class _D, class _R, class _T, class _T1>
// inline _LIBCPP_INLINE_VISIBILITY
// typename enable_if
// <
//     is_base_of<_T, typename remove_reference<_T1>::type>::value,
//     typename __ref_return1<_R _T::*, _T1>::type
// >::type
// __invoke(_R _T::* __f, _T1& __t1)
// {
//     return __t1.*__f;
// }

// forth bullet

template <class _T1, class _R, bool>
struct __4th_helper
{
};

template <class _T1, class _R>
struct __4th_helper<_T1, _R, true>
{
    typedef typename __apply_cv<decltype(*_STD::declval<_T1>()), _R>::type type;
};

template <class _R, class _T, class _T1>
inline _LIBCPP_INLINE_VISIBILITY
typename __4th_helper<_T1, _R,
                      !is_base_of<_T,
                                  typename remove_reference<_T1>::type
                                 >::value
                     >::type&
__invoke(_R _T::* __f, _T1& __t1)
{
    return (*__t1).*__f;
}

// template <class _D, class _R, class _T, class _T1>
// inline _LIBCPP_INLINE_VISIBILITY
// typename enable_if
// <
//     !is_base_of<_T, typename remove_reference<_T1>::type>::value,
//     typename __ref_return1<_R _T::*, _T1>::type
// >::type
// __invoke(_R _T::* __f, _T1 __t1)
// {
//     return (*__t1).*__f;
// }

// fifth bullet

template <class _F>
inline _LIBCPP_INLINE_VISIBILITY
decltype(declval<_F>()())
__invoke(_F __f)
{
    return __f();
}

template <class _F, class _A0>
inline _LIBCPP_INLINE_VISIBILITY
decltype(declval<_F>()(declval<_A0&>()))
__invoke(_F __f, _A0& __a0)
{
    return __f(__a0);
}

template <class _F, class _A0, class _A1>
inline _LIBCPP_INLINE_VISIBILITY
decltype(declval<_F>()(declval<_A0&>(), declval<_A1&>()))
__invoke(_F __f, _A0& __a0, _A1& __a1)
{
    return __f(__a0, __a1);
}

template <class _F, class _A0, class _A1, class _A2>
inline _LIBCPP_INLINE_VISIBILITY
decltype(declval<_F>()(declval<_A0&>(), declval<_A1&>(), declval<_A2&>()))
__invoke(_F __f, _A0& __a0, _A1& __a1, _A2& __a2)
{
    return __f(__a0, __a1, __a2);
}

// template <class _R, class _F>
// inline _LIBCPP_INLINE_VISIBILITY
// _R
// __invoke(_F& __f)
// {
//     return __f();
// }
//
// template <class _R, class _F, class _A0>
// inline _LIBCPP_INLINE_VISIBILITY
// typename enable_if
// <
//     !is_member_pointer<_F>::value,
//     _R
// >::type
// __invoke(_F& __f, _A0& __a0)
// {
//     return __f(__a0);
// }
//
// template <class _R, class _F, class _A0, class _A1>
// inline _LIBCPP_INLINE_VISIBILITY
// _R
// __invoke(_F& __f, _A0& __a0, _A1& __a1)
// {
//     return __f(__a0, __a1);
// }
//
// template <class _R, class _F, class _A0, class _A1, class _A2>
// inline _LIBCPP_INLINE_VISIBILITY
// _R
// __invoke(_F& __f, _A0& __a0, _A1& __a1, _A2& __a2)
// {
//     return __f(__a0, __a1, __a2);
// }

template <class _Tp>
struct __has_type
{
private:
    struct __two {char _; char __;};
    template <class _Up> static __two __test(...);
    template <class _Up> static char __test(typename _Up::type* = 0);
public:
    static const bool value = sizeof(__test<_Tp>(0)) == 1;
};

template <class _F, bool = __has_result_type<__weak_result_type<_F> >::value>
struct __invoke_return
{
    typedef typename __weak_result_type<_F>::result_type type;
};

template <class _F>
struct __invoke_return<_F, false>
{
    typedef decltype(__invoke(_STD::declval<_F>())) type;
};

template <class _Tp, class _A0>
struct __invoke_return0
{
    typedef decltype(__invoke(_STD::declval<_Tp>(), _STD::declval<_A0>())) type;
};

template <class _R, class _T, class _A0>
struct __invoke_return0<_R _T::*, _A0>
{
    typedef typename __apply_cv<_A0, _R>::type& type;
};

template <class _R, class _T, class _A0>
struct __invoke_return0<_R _T::*, _A0*>
{
    typedef typename __apply_cv<_A0, _R>::type& type;
};

template <class _Tp, class _A0, class _A1>
struct __invoke_return1
{
    typedef decltype(__invoke(_STD::declval<_Tp>(), _STD::declval<_A0>(),
                                                    _STD::declval<_A1>())) type;
};

template <class _Tp, class _A0, class _A1, class _A2>
struct __invoke_return2
{
    typedef decltype(__invoke(_STD::declval<_Tp>(), _STD::declval<_A0>(),
                                                    _STD::declval<_A1>(),
                                                    _STD::declval<_A2>())) type;
};

template <class _Tp>
class _LIBCPP_VISIBLE reference_wrapper
    : public __weak_result_type<_Tp>
{
public:
    // types
    typedef _Tp type;
private:
    type* __f_;

public:
    // construct/copy/destroy
    _LIBCPP_INLINE_VISIBILITY reference_wrapper(type& __f) : __f_(&__f) {}

    // access
    _LIBCPP_INLINE_VISIBILITY operator type&    () const {return *__f_;}
    _LIBCPP_INLINE_VISIBILITY          type& get() const {return *__f_;}

    // invoke

    _LIBCPP_INLINE_VISIBILITY
    typename __invoke_return<type&>::type
       operator() () const
       {
           return __invoke(get());
       }

    template <class _A0>
       _LIBCPP_INLINE_VISIBILITY
       typename __invoke_return0<type&, _A0>::type
          operator() (_A0& __a0) const
          {
              return __invoke(get(), __a0);
          }

    template <class _A0, class _A1>
       _LIBCPP_INLINE_VISIBILITY
       typename __invoke_return1<type&, _A0, _A1>::type
          operator() (_A0& __a0, _A1& __a1) const
          {
              return __invoke(get(), __a0, __a1);
          }

    template <class _A0, class _A1, class _A2>
       _LIBCPP_INLINE_VISIBILITY
       typename __invoke_return2<type&, _A0, _A1, _A2>::type
          operator() (_A0& __a0, _A1& __a1, _A2& __a2) const
          {
              return __invoke(get(), __a0, __a1, __a2);
          }
};

template <class _Tp> struct ____is_reference_wrapper : public false_type {};
template <class _Tp> struct ____is_reference_wrapper<reference_wrapper<_Tp> > : public true_type {};
template <class _Tp> struct __is_reference_wrapper
    : public ____is_reference_wrapper<typename remove_cv<_Tp>::type> {};

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

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
reference_wrapper<_Tp>
ref(reference_wrapper<_Tp> __t)
{
    return ref(__t.get());
}

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

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
reference_wrapper<const _Tp>
cref(reference_wrapper<_Tp> __t)
{
    return cref(__t.get());
}

#endif  // _LIBCPP_FUNCTIONAL_BASE_03