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nest-open-source / nest-cam / 4320010 / libcxx-ba865ff / e429766a84c8a6e303988cd81f223167ed2fd2f3 / . / libcxx / include / experimental / optional
blob: a384882a1e129e59bb9fd7a238837066dcec4d1a [file] [log] [blame]
// -*- C++ -*-
//===-------------------------- optional ----------------------------------===//
//
// 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_OPTIONAL
#define _LIBCPP_OPTIONAL
/*
optional synopsis
// C++1y
namespace std { namespace experimental { inline namespace fundamentals_v1 {
// 5.3, optional for object types
template <class T> class optional;
// 5.4, In-place construction
struct in_place_t{};
constexpr in_place_t in_place{};
// 5.5, No-value state indicator
struct nullopt_t{see below};
constexpr nullopt_t nullopt(unspecified);
// 5.6, Class bad_optional_access
class bad_optional_access;
// 5.7, Relational operators
template <class T>
constexpr bool operator==(const optional<T>&, const optional<T>&);
template <class T>
constexpr bool operator!=(const optional<T>&, const optional<T>&);
template <class T>
constexpr bool operator<(const optional<T>&, const optional<T>&);
template <class T>
constexpr bool operator>(const optional<T>&, const optional<T>&);
template <class T>
constexpr bool operator<=(const optional<T>&, const optional<T>&);
template <class T>
constexpr bool operator>=(const optional<T>&, const optional<T>&);
// 5.8, Comparison with nullopt
template <class T> constexpr bool operator==(const optional<T>&, nullopt_t) noexcept;
template <class T> constexpr bool operator==(nullopt_t, const optional<T>&) noexcept;
template <class T> constexpr bool operator!=(const optional<T>&, nullopt_t) noexcept;
template <class T> constexpr bool operator!=(nullopt_t, const optional<T>&) noexcept;
template <class T> constexpr bool operator<(const optional<T>&, nullopt_t) noexcept;
template <class T> constexpr bool operator<(nullopt_t, const optional<T>&) noexcept;
template <class T> constexpr bool operator<=(const optional<T>&, nullopt_t) noexcept;
template <class T> constexpr bool operator<=(nullopt_t, const optional<T>&) noexcept;
template <class T> constexpr bool operator>(const optional<T>&, nullopt_t) noexcept;
template <class T> constexpr bool operator>(nullopt_t, const optional<T>&) noexcept;
template <class T> constexpr bool operator>=(const optional<T>&, nullopt_t) noexcept;
template <class T> constexpr bool operator>=(nullopt_t, const optional<T>&) noexcept;
// 5.9, Comparison with T
template <class T> constexpr bool operator==(const optional<T>&, const T&);
template <class T> constexpr bool operator==(const T&, const optional<T>&);
template <class T> constexpr bool operator!=(const optional<T>&, const T&);
template <class T> constexpr bool operator!=(const T&, const optional<T>&);
template <class T> constexpr bool operator<(const optional<T>&, const T&);
template <class T> constexpr bool operator<(const T&, const optional<T>&);
template <class T> constexpr bool operator<=(const optional<T>&, const T&);
template <class T> constexpr bool operator<=(const T&, const optional<T>&);
template <class T> constexpr bool operator>(const optional<T>&, const T&);
template <class T> constexpr bool operator>(const T&, const optional<T>&);
template <class T> constexpr bool operator>=(const optional<T>&, const T&);
template <class T> constexpr bool operator>=(const T&, const optional<T>&);
// 5.10, Specialized algorithms
template <class T> void swap(optional<T>&, optional<T>&) noexcept(see below);
template <class T> constexpr optional<see below> make_optional(T&&);
template <class T>
class optional
{
public:
typedef T value_type;
// 5.3.1, Constructors
constexpr optional() noexcept;
constexpr optional(nullopt_t) noexcept;
optional(const optional&);
optional(optional&&) noexcept(see below);
constexpr optional(const T&);
constexpr optional(T&&);
template <class... Args> constexpr explicit optional(in_place_t, Args&&...);
template <class U, class... Args>
constexpr explicit optional(in_place_t, initializer_list<U>, Args&&...);
// 5.3.2, Destructor
~optional();
// 5.3.3, Assignment
optional& operator=(nullopt_t) noexcept;
optional& operator=(const optional&);
optional& operator=(optional&&) noexcept(see below);
template <class U> optional& operator=(U&&);
template <class... Args> void emplace(Args&&...);
template <class U, class... Args>
void emplace(initializer_list<U>, Args&&...);
// 5.3.4, Swap
void swap(optional&) noexcept(see below);
// 5.3.5, Observers
constexpr T const* operator ->() const;
constexpr T* operator ->();
constexpr T const& operator *() const &;
constexpr T& operator *() &;
constexpr T&& operator *() &&;
constexpr const T&& operator *() const &&;
constexpr explicit operator bool() const noexcept;
constexpr T const& value() const &;
constexpr T& value() &;
constexpr T&& value() &&;
constexpr const T&& value() const &&;
template <class U> constexpr T value_or(U&&) const &;
template <class U> constexpr T value_or(U&&) &&;
private:
T* val; // exposition only
};
} // namespace fundamentals_v1
} // namespace experimental
// 5.11, Hash support
template <class T> struct hash;
template <class T> struct hash<experimental::optional<T>>;
} // namespace std
*/
#include <experimental/__config>
#include <functional>
#include <stdexcept>
_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
class _LIBCPP_EXCEPTION_ABI bad_optional_access
: public std::logic_error
{
public:
bad_optional_access() : std::logic_error("Bad optional Access") {}
// Get the key function ~bad_optional_access() into the dylib
virtual ~bad_optional_access() _NOEXCEPT;
};
_LIBCPP_END_NAMESPACE_EXPERIMENTAL
#if _LIBCPP_STD_VER > 11
#include <initializer_list>
#include <type_traits>
#include <new>
#include <__functional_base>
#include <__undef_min_max>
#include <__debug>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_LFTS
struct in_place_t {};
constexpr in_place_t in_place{};
struct nullopt_t
{
explicit constexpr nullopt_t(int) noexcept {}
};
constexpr nullopt_t nullopt{0};
template <class _Tp, bool = is_trivially_destructible<_Tp>::value>
class __optional_storage
{
protected:
typedef _Tp value_type;
union
{
char __null_state_;
value_type __val_;
};
bool __engaged_ = false;
_LIBCPP_INLINE_VISIBILITY
~__optional_storage()
{
if (__engaged_)
__val_.~value_type();
}
_LIBCPP_INLINE_VISIBILITY
constexpr __optional_storage() noexcept
: __null_state_('\0') {}
_LIBCPP_INLINE_VISIBILITY
__optional_storage(const __optional_storage& __x)
: __engaged_(__x.__engaged_)
{
if (__engaged_)
::new(_VSTD::addressof(__val_)) value_type(__x.__val_);
}
_LIBCPP_INLINE_VISIBILITY
__optional_storage(__optional_storage&& __x)
noexcept(is_nothrow_move_constructible<value_type>::value)
: __engaged_(__x.__engaged_)
{
if (__engaged_)
::new(_VSTD::addressof(__val_)) value_type(_VSTD::move(__x.__val_));
}
_LIBCPP_INLINE_VISIBILITY
constexpr __optional_storage(const value_type& __v)
: __val_(__v),
__engaged_(true) {}
_LIBCPP_INLINE_VISIBILITY
constexpr __optional_storage(value_type&& __v)
: __val_(_VSTD::move(__v)),
__engaged_(true) {}
template <class... _Args>
_LIBCPP_INLINE_VISIBILITY
constexpr
explicit __optional_storage(in_place_t, _Args&&... __args)
: __val_(_VSTD::forward<_Args>(__args)...),
__engaged_(true) {}
};
template <class _Tp>
class __optional_storage<_Tp, true>
{
protected:
typedef _Tp value_type;
union
{
char __null_state_;
value_type __val_;
};
bool __engaged_ = false;
_LIBCPP_INLINE_VISIBILITY
constexpr __optional_storage() noexcept
: __null_state_('\0') {}
_LIBCPP_INLINE_VISIBILITY
__optional_storage(const __optional_storage& __x)
: __engaged_(__x.__engaged_)
{
if (__engaged_)
::new(_VSTD::addressof(__val_)) value_type(__x.__val_);
}
_LIBCPP_INLINE_VISIBILITY
__optional_storage(__optional_storage&& __x)
noexcept(is_nothrow_move_constructible<value_type>::value)
: __engaged_(__x.__engaged_)
{
if (__engaged_)
::new(_VSTD::addressof(__val_)) value_type(_VSTD::move(__x.__val_));
}
_LIBCPP_INLINE_VISIBILITY
constexpr __optional_storage(const value_type& __v)
: __val_(__v),
__engaged_(true) {}
_LIBCPP_INLINE_VISIBILITY
constexpr __optional_storage(value_type&& __v)
: __val_(_VSTD::move(__v)),
__engaged_(true) {}
template <class... _Args>
_LIBCPP_INLINE_VISIBILITY
constexpr
explicit __optional_storage(in_place_t, _Args&&... __args)
: __val_(_VSTD::forward<_Args>(__args)...),
__engaged_(true) {}
};
template <class _Tp>
class optional
: private __optional_storage<_Tp>
{
typedef __optional_storage<_Tp> __base;
public:
typedef _Tp value_type;
static_assert(!is_reference<value_type>::value,
"Instantiation of optional with a reference type is ill-formed.");
static_assert(!is_same<typename remove_cv<value_type>::type, in_place_t>::value,
"Instantiation of optional with a in_place_t type is ill-formed.");
static_assert(!is_same<typename remove_cv<value_type>::type, nullopt_t>::value,
"Instantiation of optional with a nullopt_t type is ill-formed.");
static_assert(is_object<value_type>::value,
"Instantiation of optional with a non-object type is undefined behavior.");
static_assert(is_nothrow_destructible<value_type>::value,
"Instantiation of optional with an object type that is not noexcept destructible is undefined behavior.");
_LIBCPP_INLINE_VISIBILITY constexpr optional() noexcept {}
_LIBCPP_INLINE_VISIBILITY optional(const optional&) = default;
_LIBCPP_INLINE_VISIBILITY optional(optional&&) = default;
_LIBCPP_INLINE_VISIBILITY ~optional() = default;
_LIBCPP_INLINE_VISIBILITY constexpr optional(nullopt_t) noexcept {}
_LIBCPP_INLINE_VISIBILITY constexpr optional(const value_type& __v)
: __base(__v) {}
_LIBCPP_INLINE_VISIBILITY constexpr optional(value_type&& __v)
: __base(_VSTD::move(__v)) {}
template <class... _Args,
class = typename enable_if
<
is_constructible<value_type, _Args...>::value
>::type
>
_LIBCPP_INLINE_VISIBILITY
constexpr
explicit optional(in_place_t, _Args&&... __args)
: __base(in_place, _VSTD::forward<_Args>(__args)...) {}
template <class _Up, class... _Args,
class = typename enable_if
<
is_constructible<value_type, initializer_list<_Up>&, _Args...>::value
>::type
>
_LIBCPP_INLINE_VISIBILITY
constexpr
explicit optional(in_place_t, initializer_list<_Up> __il, _Args&&... __args)
: __base(in_place, __il, _VSTD::forward<_Args>(__args)...) {}
_LIBCPP_INLINE_VISIBILITY
optional& operator=(nullopt_t) noexcept
{
if (this->__engaged_)
{
this->__val_.~value_type();
this->__engaged_ = false;
}
return *this;
}
_LIBCPP_INLINE_VISIBILITY
optional&
operator=(const optional& __opt)
{
if (this->__engaged_ == __opt.__engaged_)
{
if (this->__engaged_)
this->__val_ = __opt.__val_;
}
else
{
if (this->__engaged_)
this->__val_.~value_type();
else
::new(_VSTD::addressof(this->__val_)) value_type(__opt.__val_);
this->__engaged_ = __opt.__engaged_;
}
return *this;
}
_LIBCPP_INLINE_VISIBILITY
optional&
operator=(optional&& __opt)
noexcept(is_nothrow_move_assignable<value_type>::value &&
is_nothrow_move_constructible<value_type>::value)
{
if (this->__engaged_ == __opt.__engaged_)
{
if (this->__engaged_)
this->__val_ = _VSTD::move(__opt.__val_);
}
else
{
if (this->__engaged_)
this->__val_.~value_type();
else
::new(_VSTD::addressof(this->__val_)) value_type(_VSTD::move(__opt.__val_));
this->__engaged_ = __opt.__engaged_;
}
return *this;
}
template <class _Up,
class = typename enable_if
<
is_same<typename remove_reference<_Up>::type, value_type>::value &&
is_constructible<value_type, _Up>::value &&
is_assignable<value_type&, _Up>::value
>::type
>
_LIBCPP_INLINE_VISIBILITY
optional&
operator=(_Up&& __v)
{
if (this->__engaged_)
this->__val_ = _VSTD::forward<_Up>(__v);
else
{
::new(_VSTD::addressof(this->__val_)) value_type(_VSTD::forward<_Up>(__v));
this->__engaged_ = true;
}
return *this;
}
template <class... _Args,
class = typename enable_if
<
is_constructible<value_type, _Args...>::value
>::type
>
_LIBCPP_INLINE_VISIBILITY
void
emplace(_Args&&... __args)
{
*this = nullopt;
::new(_VSTD::addressof(this->__val_)) value_type(_VSTD::forward<_Args>(__args)...);
this->__engaged_ = true;
}
template <class _Up, class... _Args,
class = typename enable_if
<
is_constructible<value_type, initializer_list<_Up>&, _Args...>::value
>::type
>
_LIBCPP_INLINE_VISIBILITY
void
emplace(initializer_list<_Up> __il, _Args&&... __args)
{
*this = nullopt;
::new(_VSTD::addressof(this->__val_)) value_type(__il, _VSTD::forward<_Args>(__args)...);
this->__engaged_ = true;
}
_LIBCPP_INLINE_VISIBILITY
void
swap(optional& __opt)
noexcept(is_nothrow_move_constructible<value_type>::value &&
__is_nothrow_swappable<value_type>::value)
{
using _VSTD::swap;
if (this->__engaged_ == __opt.__engaged_)
{
if (this->__engaged_)
swap(this->__val_, __opt.__val_);
}
else
{
if (this->__engaged_)
{
::new(_VSTD::addressof(__opt.__val_)) value_type(_VSTD::move(this->__val_));
this->__val_.~value_type();
}
else
{
::new(_VSTD::addressof(this->__val_)) value_type(_VSTD::move(__opt.__val_));
__opt.__val_.~value_type();
}
swap(this->__engaged_, __opt.__engaged_);
}
}
_LIBCPP_INLINE_VISIBILITY
constexpr
value_type const*
operator->() const
{
_LIBCPP_ASSERT(this->__engaged_, "optional operator-> called for disengaged value");
return __operator_arrow(__has_operator_addressof<value_type>{});
}
_LIBCPP_INLINE_VISIBILITY
value_type*
operator->()
{
_LIBCPP_ASSERT(this->__engaged_, "optional operator-> called for disengaged value");
return _VSTD::addressof(this->__val_);
}
_LIBCPP_INLINE_VISIBILITY
constexpr
const value_type&
operator*() const
{
_LIBCPP_ASSERT(this->__engaged_, "optional operator* called for disengaged value");
return this->__val_;
}
_LIBCPP_INLINE_VISIBILITY
value_type&
operator*()
{
_LIBCPP_ASSERT(this->__engaged_, "optional operator* called for disengaged value");
return this->__val_;
}
_LIBCPP_INLINE_VISIBILITY
constexpr explicit operator bool() const noexcept {return this->__engaged_;}
_LIBCPP_INLINE_VISIBILITY
constexpr value_type const& value() const
{
if (!this->__engaged_)
throw bad_optional_access();
return this->__val_;
}
_LIBCPP_INLINE_VISIBILITY
value_type& value()
{
if (!this->__engaged_)
throw bad_optional_access();
return this->__val_;
}
template <class _Up>
_LIBCPP_INLINE_VISIBILITY
constexpr value_type value_or(_Up&& __v) const&
{
static_assert(is_copy_constructible<value_type>::value,
"optional<T>::value_or: T must be copy constructible");
static_assert(is_convertible<_Up, value_type>::value,
"optional<T>::value_or: U must be convertible to T");
return this->__engaged_ ? this->__val_ :
static_cast<value_type>(_VSTD::forward<_Up>(__v));
}
template <class _Up>
_LIBCPP_INLINE_VISIBILITY
value_type value_or(_Up&& __v) &&
{
static_assert(is_move_constructible<value_type>::value,
"optional<T>::value_or: T must be move constructible");
static_assert(is_convertible<_Up, value_type>::value,
"optional<T>::value_or: U must be convertible to T");
return this->__engaged_ ? _VSTD::move(this->__val_) :
static_cast<value_type>(_VSTD::forward<_Up>(__v));
}
private:
_LIBCPP_INLINE_VISIBILITY
value_type const*
__operator_arrow(true_type) const
{
return _VSTD::addressof(this->__val_);
}
_LIBCPP_INLINE_VISIBILITY
constexpr
value_type const*
__operator_arrow(false_type) const
{
return &this->__val_;
}
};
// Comparisons between optionals
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator==(const optional<_Tp>& __x, const optional<_Tp>& __y)
{
if (static_cast<bool>(__x) != static_cast<bool>(__y))
return false;
if (!static_cast<bool>(__x))
return true;
return *__x == *__y;
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator!=(const optional<_Tp>& __x, const optional<_Tp>& __y)
{
return !(__x == __y);
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator<(const optional<_Tp>& __x, const optional<_Tp>& __y)
{
if (!static_cast<bool>(__y))
return false;
if (!static_cast<bool>(__x))
return true;
return *__x < *__y;
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator>(const optional<_Tp>& __x, const optional<_Tp>& __y)
{
return __y < __x;
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator<=(const optional<_Tp>& __x, const optional<_Tp>& __y)
{
return !(__y < __x);
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator>=(const optional<_Tp>& __x, const optional<_Tp>& __y)
{
return !(__x < __y);
}
// Comparisons with nullopt
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator==(const optional<_Tp>& __x, nullopt_t) noexcept
{
return !static_cast<bool>(__x);
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator==(nullopt_t, const optional<_Tp>& __x) noexcept
{
return !static_cast<bool>(__x);
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator!=(const optional<_Tp>& __x, nullopt_t) noexcept
{
return static_cast<bool>(__x);
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator!=(nullopt_t, const optional<_Tp>& __x) noexcept
{
return static_cast<bool>(__x);
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator<(const optional<_Tp>&, nullopt_t) noexcept
{
return false;
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator<(nullopt_t, const optional<_Tp>& __x) noexcept
{
return static_cast<bool>(__x);
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator<=(const optional<_Tp>& __x, nullopt_t) noexcept
{
return !static_cast<bool>(__x);
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator<=(nullopt_t, const optional<_Tp>& __x) noexcept
{
return true;
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator>(const optional<_Tp>& __x, nullopt_t) noexcept
{
return static_cast<bool>(__x);
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator>(nullopt_t, const optional<_Tp>& __x) noexcept
{
return false;
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator>=(const optional<_Tp>&, nullopt_t) noexcept
{
return true;
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator>=(nullopt_t, const optional<_Tp>& __x) noexcept
{
return !static_cast<bool>(__x);
}
// Comparisons with T
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator==(const optional<_Tp>& __x, const _Tp& __v)
{
return static_cast<bool>(__x) ? *__x == __v : false;
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator==(const _Tp& __v, const optional<_Tp>& __x)
{
return static_cast<bool>(__x) ? *__x == __v : false;
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator!=(const optional<_Tp>& __x, const _Tp& __v)
{
return static_cast<bool>(__x) ? !(*__x == __v) : true;
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator!=(const _Tp& __v, const optional<_Tp>& __x)
{
return static_cast<bool>(__x) ? !(*__x == __v) : true;
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator<(const optional<_Tp>& __x, const _Tp& __v)
{
return static_cast<bool>(__x) ? less<_Tp>{}(*__x, __v) : true;
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator<(const _Tp& __v, const optional<_Tp>& __x)
{
return static_cast<bool>(__x) ? less<_Tp>{}(__v, *__x) : false;
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator<=(const optional<_Tp>& __x, const _Tp& __v)
{
return !(__x > __v);
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator<=(const _Tp& __v, const optional<_Tp>& __x)
{
return !(__v > __x);
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator>(const optional<_Tp>& __x, const _Tp& __v)
{
return static_cast<bool>(__x) ? __v < __x : false;
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator>(const _Tp& __v, const optional<_Tp>& __x)
{
return static_cast<bool>(__x) ? __x < __v : true;
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator>=(const optional<_Tp>& __x, const _Tp& __v)
{
return !(__x < __v);
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
bool
operator>=(const _Tp& __v, const optional<_Tp>& __x)
{
return !(__v < __x);
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(optional<_Tp>& __x, optional<_Tp>& __y) noexcept(noexcept(__x.swap(__y)))
{
__x.swap(__y);
}
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY
constexpr
optional<typename decay<_Tp>::type>
make_optional(_Tp&& __v)
{
return optional<typename decay<_Tp>::type>(_VSTD::forward<_Tp>(__v));
}
_LIBCPP_END_NAMESPACE_LFTS
_LIBCPP_BEGIN_NAMESPACE_STD
template <class _Tp>
struct _LIBCPP_TYPE_VIS_ONLY hash<std::experimental::optional<_Tp> >
{
typedef std::experimental::optional<_Tp> argument_type;
typedef size_t result_type;
_LIBCPP_INLINE_VISIBILITY
result_type operator()(const argument_type& __opt) const _NOEXCEPT
{
return static_cast<bool>(__opt) ? hash<_Tp>()(*__opt) : 0;
}
};
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP_STD_VER > 11
#endif // _LIBCPP_OPTIONAL