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lokinet/include/tl/optional.hpp

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add std::optional backport option for cxx11
2018-11-19 16:31:12 +00:00
///
// optional - An implementation of std::optional with extensions
// Written in 2017 by Simon Brand (@TartanLlama)
//
// To the extent possible under law, the author(s) have dedicated all
// copyright and related and neighboring rights to this software to the
// public domain worldwide. This software is distributed without any warranty.
//
// You should have received a copy of the CC0 Public Domain Dedication
// along with this software. If not, see
// <http://creativecommons.org/publicdomain/zero/1.0/>.
///
#ifndef TL_OPTIONAL_HPP
#define TL_OPTIONAL_HPP
#define TL_OPTIONAL_VERSION_MAJOR 0
#define TL_OPTIONAL_VERSION_MINOR 5
#include <exception>
#include <functional>
#include <new>
#include <type_traits>
#include <utility>
#if (defined(_MSC_VER) && _MSC_VER == 1900)
#define TL_OPTIONAL_MSVC2015
#endif
#if (defined(__GNUC__) && __GNUC__ == 4 && __GNUC_MINOR__ <= 9 && \
!defined(__clang__))
#define TL_OPTIONAL_GCC49
#endif
#if (defined(__GNUC__) && __GNUC__ == 5 && __GNUC_MINOR__ <= 4 && \
!defined(__clang__))
#define TL_OPTIONAL_GCC54
#endif
#if (defined(__GNUC__) && __GNUC__ == 5 && __GNUC_MINOR__ <= 5 && \
!defined(__clang__))
#define TL_OPTIONAL_GCC55
#endif
#if (defined(__GNUC__) && __GNUC__ == 4 && __GNUC_MINOR__ <= 9 && \
!defined(__clang__))
// GCC < 5 doesn't support overloading on const&& for member functions
#define TL_OPTIONAL_NO_CONSTRR
// GCC < 5 doesn't support some standard C++11 type traits
#define TL_OPTIONAL_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T) \
std::has_trivial_copy_constructor<T>::value
#define TL_OPTIONAL_IS_TRIVIALLY_COPY_ASSIGNABLE(T) std::has_trivial_copy_assign<T>::value
// This one will be different for GCC 5.7 if it's ever supported
#define TL_OPTIONAL_IS_TRIVIALLY_DESTRUCTIBLE(T) std::is_trivially_destructible<T>::value
// GCC 5 < v < 8 has a bug in is_trivially_copy_constructible which breaks std::vector
// for non-copyable types
#elif (defined(__GNUC__) && __GNUC__ < 8 && \
!defined(__clang__))
#ifndef TL_GCC_LESS_8_TRIVIALLY_COPY_CONSTRUCTIBLE_MUTEX
#define TL_GCC_LESS_8_TRIVIALLY_COPY_CONSTRUCTIBLE_MUTEX
namespace tl {
namespace detail {
template<class T>
struct is_trivially_copy_constructible : std::is_trivially_copy_constructible<T>{};
#ifdef _GLIBCXX_VECTOR
template<class T, class A>
struct is_trivially_copy_constructible<std::vector<T,A>>
: std::is_trivially_copy_constructible<T>{};
#endif
}
}
#endif
#define TL_OPTIONAL_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T) \
tl::detail::is_trivially_copy_constructible<T>::value
#define TL_OPTIONAL_IS_TRIVIALLY_COPY_ASSIGNABLE(T) \
std::is_trivially_copy_assignable<T>::value
#define TL_OPTIONAL_IS_TRIVIALLY_DESTRUCTIBLE(T) std::is_trivially_destructible<T>::value
#else
#define TL_OPTIONAL_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T) \
std::is_trivially_copy_constructible<T>::value
#define TL_OPTIONAL_IS_TRIVIALLY_COPY_ASSIGNABLE(T) \
std::is_trivially_copy_assignable<T>::value
#define TL_OPTIONAL_IS_TRIVIALLY_DESTRUCTIBLE(T) std::is_trivially_destructible<T>::value
#endif
#if __cplusplus > 201103L
#define TL_OPTIONAL_CXX14
#endif
// constexpr implies const in C++11, not C++14
#if (__cplusplus == 201103L || defined(TL_OPTIONAL_MSVC2015) || \
defined(TL_OPTIONAL_GCC49))
/// \exclude
#define TL_OPTIONAL_11_CONSTEXPR
#else
/// \exclude
#define TL_OPTIONAL_11_CONSTEXPR constexpr
#endif
namespace tl {
#ifndef TL_MONOSTATE_INPLACE_MUTEX
#define TL_MONOSTATE_INPLACE_MUTEX
/// \brief Used to represent an optional with no data; essentially a bool
class monostate {};
/// \brief A tag type to tell optional to construct its value in-place
struct in_place_t {
explicit in_place_t() = default;
};
/// \brief A tag to tell optional to construct its value in-place
static constexpr in_place_t in_place{};
#endif
template <class T> class optional;
/// \exclude
namespace detail {
#ifndef TL_TRAITS_MUTEX
#define TL_TRAITS_MUTEX
// C++14-style aliases for brevity
template <class T> using remove_const_t = typename std::remove_const<T>::type;
template <class T>
using remove_reference_t = typename std::remove_reference<T>::type;
template <class T> using decay_t = typename std::decay<T>::type;
template <bool E, class T = void>
using enable_if_t = typename std::enable_if<E, T>::type;
template <bool B, class T, class F>
using conditional_t = typename std::conditional<B, T, F>::type;
// std::conjunction from C++17
template <class...> struct conjunction : std::true_type {};
template <class B> struct conjunction<B> : B {};
template <class B, class... Bs>
struct conjunction<B, Bs...>
: std::conditional<bool(B::value), conjunction<Bs...>, B>::type {};
#if defined(_LIBCPP_VERSION) && __cplusplus == 201103L
#define TL_OPTIONAL_LIBCXX_MEM_FN_WORKAROUND
#endif
// In C++11 mode, there's an issue in libc++'s std::mem_fn
// which results in a hard-error when using it in a noexcept expression
// in some cases. This is a check to workaround the common failing case.
#ifdef TL_OPTIONAL_LIBCXX_MEM_FN_WORKAROUND
template <class T> struct is_pointer_to_non_const_member_func : std::false_type{};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*) (Args...)> : std::true_type{};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*) (Args...)&> : std::true_type{};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*) (Args...)&&> : std::true_type{};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*) (Args...) volatile> : std::true_type{};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*) (Args...) volatile&> : std::true_type{};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*) (Args...) volatile&&> : std::true_type{};
template <class T> struct is_const_or_const_ref : std::false_type{};
template <class T> struct is_const_or_const_ref<T const&> : std::true_type{};
template <class T> struct is_const_or_const_ref<T const> : std::true_type{};
#endif
// std::invoke from C++17
// https://stackoverflow.com/questions/38288042/c11-14-invoke-workaround
template <typename Fn, typename... Args,
#ifdef TL_OPTIONAL_LIBCXX_MEM_FN_WORKAROUND
typename = enable_if_t<!(is_pointer_to_non_const_member_func<Fn>::value
&& is_const_or_const_ref<Args...>::value)>,
#endif
typename = enable_if_t<std::is_member_pointer<decay_t<Fn>>::value>,
int = 0>
constexpr auto invoke(Fn &&f, Args &&... args) noexcept(
noexcept(std::mem_fn(f)(std::forward<Args>(args)...)))
-> decltype(std::mem_fn(f)(std::forward<Args>(args)...)) {
return std::mem_fn(f)(std::forward<Args>(args)...);
}
template <typename Fn, typename... Args,
typename = enable_if_t<!std::is_member_pointer<decay_t<Fn>>::value>>
constexpr auto invoke(Fn &&f, Args &&... args) noexcept(
noexcept(std::forward<Fn>(f)(std::forward<Args>(args)...)))
-> decltype(std::forward<Fn>(f)(std::forward<Args>(args)...)) {
return std::forward<Fn>(f)(std::forward<Args>(args)...);
}
// std::invoke_result from C++17
template <class F, class, class... Us> struct invoke_result_impl;
template <class F, class... Us>
struct invoke_result_impl<
F, decltype(detail::invoke(std::declval<F>(), std::declval<Us>()...), void()),
Us...> {
using type = decltype(detail::invoke(std::declval<F>(), std::declval<Us>()...));
};
template <class F, class... Us>
using invoke_result = invoke_result_impl<F, void, Us...>;
template <class F, class... Us>
using invoke_result_t = typename invoke_result<F, Us...>::type;
#endif
// std::void_t from C++17
template <class...> struct voider { using type = void; };
template <class... Ts> using void_t = typename voider<Ts...>::type;
// Trait for checking if a type is a tl::optional
template <class T> struct is_optional_impl : std::false_type {};
template <class T> struct is_optional_impl<optional<T>> : std::true_type {};
template <class T> using is_optional = is_optional_impl<decay_t<T>>;
// Change void to tl::monostate
template <class U>
using fixup_void = conditional_t<std::is_void<U>::value, monostate, U>;
template <class F, class U, class = invoke_result_t<F, U>>
using get_map_return = optional<fixup_void<invoke_result_t<F, U>>>;
// Check if invoking F for some Us returns void
template <class F, class = void, class... U> struct returns_void_impl;
template <class F, class... U>
struct returns_void_impl<F, void_t<invoke_result_t<F, U...>>, U...>
: std::is_void<invoke_result_t<F, U...>> {};
template <class F, class... U>
using returns_void = returns_void_impl<F, void, U...>;
template <class T, class... U>
using enable_if_ret_void = enable_if_t<returns_void<T &&, U...>::value>;
template <class T, class... U>
using disable_if_ret_void = enable_if_t<!returns_void<T &&, U...>::value>;
template <class T, class U>
using enable_forward_value =
detail::enable_if_t<std::is_constructible<T, U &&>::value &&
!std::is_same<detail::decay_t<U>, in_place_t>::value &&
!std::is_same<optional<T>, detail::decay_t<U>>::value>;
template <class T, class U, class Other>
using enable_from_other = detail::enable_if_t<
std::is_constructible<T, Other>::value &&
!std::is_constructible<T, optional<U> &>::value &&
!std::is_constructible<T, optional<U> &&>::value &&
!std::is_constructible<T, const optional<U> &>::value &&
!std::is_constructible<T, const optional<U> &&>::value &&
!std::is_convertible<optional<U> &, T>::value &&
!std::is_convertible<optional<U> &&, T>::value &&
!std::is_convertible<const optional<U> &, T>::value &&
!std::is_convertible<const optional<U> &&, T>::value>;
template <class T, class U>
using enable_assign_forward = detail::enable_if_t<
!std::is_same<optional<T>, detail::decay_t<U>>::value &&
!detail::conjunction<std::is_scalar<T>,
std::is_same<T, detail::decay_t<U>>>::value &&
std::is_constructible<T, U>::value && std::is_assignable<T &, U>::value>;
template <class T, class U, class Other>
using enable_assign_from_other = detail::enable_if_t<
std::is_constructible<T, Other>::value &&
std::is_assignable<T &, Other>::value &&
!std::is_constructible<T, optional<U> &>::value &&
!std::is_constructible<T, optional<U> &&>::value &&
!std::is_constructible<T, const optional<U> &>::value &&
!std::is_constructible<T, const optional<U> &&>::value &&
!std::is_convertible<optional<U> &, T>::value &&
!std::is_convertible<optional<U> &&, T>::value &&
!std::is_convertible<const optional<U> &, T>::value &&
!std::is_convertible<const optional<U> &&, T>::value &&
!std::is_assignable<T &, optional<U> &>::value &&
!std::is_assignable<T &, optional<U> &&>::value &&
!std::is_assignable<T &, const optional<U> &>::value &&
!std::is_assignable<T &, const optional<U> &&>::value>;
#ifdef _MSC_VER
// TODO make a version which works with MSVC
template <class T, class U = T> struct is_swappable : std::true_type {};
template <class T, class U = T> struct is_nothrow_swappable : std::true_type {};
#else
// https://stackoverflow.com/questions/26744589/what-is-a-proper-way-to-implement-is-swappable-to-test-for-the-swappable-concept
namespace swap_adl_tests {
// if swap ADL finds this then it would call std::swap otherwise (same
// signature)
struct tag {};
template <class T> tag swap(T &, T &);
template <class T, std::size_t N> tag swap(T (&a)[N], T (&b)[N]);
// helper functions to test if an unqualified swap is possible, and if it
// becomes std::swap
template <class, class> std::false_type can_swap(...) noexcept(false);
template <class T, class U,
class = decltype(swap(std::declval<T &>(), std::declval<U &>()))>
std::true_type can_swap(int) noexcept(noexcept(swap(std::declval<T &>(),
std::declval<U &>())));
template <class, class> std::false_type uses_std(...);
template <class T, class U>
std::is_same<decltype(swap(std::declval<T &>(), std::declval<U &>())), tag>
uses_std(int);
template <class T>
struct is_std_swap_noexcept
: std::integral_constant<bool,
std::is_nothrow_move_constructible<T>::value &&
std::is_nothrow_move_assignable<T>::value> {};
template <class T, std::size_t N>
struct is_std_swap_noexcept<T[N]> : is_std_swap_noexcept<T> {};
template <class T, class U>
struct is_adl_swap_noexcept
: std::integral_constant<bool, noexcept(can_swap<T, U>(0))> {};
} // namespace swap_adl_tests
template <class T, class U = T>
struct is_swappable
: std::integral_constant<
bool,
decltype(detail::swap_adl_tests::can_swap<T, U>(0))::value &&
(!decltype(detail::swap_adl_tests::uses_std<T, U>(0))::value ||
(std::is_move_assignable<T>::value &&
std::is_move_constructible<T>::value))> {};
template <class T, std::size_t N>
struct is_swappable<T[N], T[N]>
: std::integral_constant<
bool,
decltype(detail::swap_adl_tests::can_swap<T[N], T[N]>(0))::value &&
(!decltype(
detail::swap_adl_tests::uses_std<T[N], T[N]>(0))::value ||
is_swappable<T, T>::value)> {};
template <class T, class U = T>
struct is_nothrow_swappable
: std::integral_constant<
bool,
is_swappable<T, U>::value &&
((decltype(detail::swap_adl_tests::uses_std<T, U>(0))::value
&&detail::swap_adl_tests::is_std_swap_noexcept<T>::value) ||
(!decltype(detail::swap_adl_tests::uses_std<T, U>(0))::value &&
detail::swap_adl_tests::is_adl_swap_noexcept<T,
U>::value))> {
};
#endif
// The storage base manages the actual storage, and correctly propagates
// trivial destruction from T. This case is for when T is not trivially
// destructible.
template <class T, bool = ::std::is_trivially_destructible<T>::value>
struct optional_storage_base {
TL_OPTIONAL_11_CONSTEXPR optional_storage_base() noexcept
: m_dummy(), m_has_value(false) {}
template <class... U>
TL_OPTIONAL_11_CONSTEXPR optional_storage_base(in_place_t, U &&... u)
: m_value(std::forward<U>(u)...), m_has_value(true) {}
~optional_storage_base() {
if (m_has_value) {
m_value.~T();
m_has_value = false;
}
}
struct dummy {};
union {
dummy m_dummy;
T m_value;
};
bool m_has_value;
};
// This case is for when T is trivially destructible.
template <class T> struct optional_storage_base<T, true> {
TL_OPTIONAL_11_CONSTEXPR optional_storage_base() noexcept
: m_dummy(), m_has_value(false) {}
template <class... U>
TL_OPTIONAL_11_CONSTEXPR optional_storage_base(in_place_t, U &&... u)
: m_value(std::forward<U>(u)...), m_has_value(true) {}
// No destructor, so this class is trivially destructible
struct dummy {};
union {
dummy m_dummy;
T m_value;
};
bool m_has_value = false;
};
// This base class provides some handy member functions which can be used in
// further derived classes
template <class T> struct optional_operations_base : optional_storage_base<T> {
using optional_storage_base<T>::optional_storage_base;
void hard_reset() noexcept {
get().~T();
this->m_has_value = false;
}
template <class... Args> void construct(Args &&... args) noexcept {
new (std::addressof(this->m_value)) T(std::forward<Args>(args)...);
this->m_has_value = true;
}
template <class Opt> void assign(Opt &&rhs) {
if (this->has_value()) {
if (rhs.has_value()) {
this->m_value = std::forward<Opt>(rhs).get();
} else {
this->m_value.~T();
this->m_has_value = false;
}
}
else if (rhs.has_value()) {
construct(std::forward<Opt>(rhs).get());
}
}
bool has_value() const { return this->m_has_value; }
TL_OPTIONAL_11_CONSTEXPR T &get() & { return this->m_value; }
TL_OPTIONAL_11_CONSTEXPR const T &get() const & { return this->m_value; }
TL_OPTIONAL_11_CONSTEXPR T &&get() && { return std::move(this->m_value); }
#ifndef TL_OPTIONAL_NO_CONSTRR
constexpr const T &&get() const && { return std::move(this->m_value); }
#endif
};
// This class manages conditionally having a trivial copy constructor
// This specialization is for when T is trivially copy constructible
template <class T, bool = TL_OPTIONAL_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T)>
struct optional_copy_base : optional_operations_base<T> {
using optional_operations_base<T>::optional_operations_base;
};
// This specialization is for when T is not trivially copy constructible
template <class T>
struct optional_copy_base<T, false> : optional_operations_base<T> {
using optional_operations_base<T>::optional_operations_base;
optional_copy_base() = default;
optional_copy_base(const optional_copy_base &rhs) {
if (rhs.has_value()) {
this->construct(rhs.get());
} else {
this->m_has_value = false;
}
}
optional_copy_base(optional_copy_base &&rhs) = default;
optional_copy_base &operator=(const optional_copy_base &rhs) = default;
optional_copy_base &operator=(optional_copy_base &&rhs) = default;
};
// This class manages conditionally having a trivial move constructor
// Unfortunately there's no way to achieve this in GCC < 5 AFAIK, since it
// doesn't implement an analogue to std::is_trivially_move_constructible. We
// have to make do with a non-trivial move constructor even if T is trivially
// move constructible
#ifndef TL_OPTIONAL_GCC49
template <class T, bool = std::is_trivially_move_constructible<T>::value>
struct optional_move_base : optional_copy_base<T> {
using optional_copy_base<T>::optional_copy_base;
};
#else
template <class T, bool = false> struct optional_move_base;
#endif
template <class T> struct optional_move_base<T, false> : optional_copy_base<T> {
using optional_copy_base<T>::optional_copy_base;
optional_move_base() = default;
optional_move_base(const optional_move_base &rhs) = default;
optional_move_base(optional_move_base &&rhs) noexcept(
std::is_nothrow_move_constructible<T>::value) {
if (rhs.has_value()) {
this->construct(std::move(rhs.get()));
} else {
this->m_has_value = false;
}
}
optional_move_base &operator=(const optional_move_base &rhs) = default;
optional_move_base &operator=(optional_move_base &&rhs) = default;
};
// This class manages conditionally having a trivial copy assignment operator
template <class T, bool = TL_OPTIONAL_IS_TRIVIALLY_COPY_ASSIGNABLE(T) &&
TL_OPTIONAL_IS_TRIVIALLY_COPY_CONSTRUCTIBLE(T) &&
TL_OPTIONAL_IS_TRIVIALLY_DESTRUCTIBLE(T)>
struct optional_copy_assign_base : optional_move_base<T> {
using optional_move_base<T>::optional_move_base;
};
template <class T>
struct optional_copy_assign_base<T, false> : optional_move_base<T> {
using optional_move_base<T>::optional_move_base;
optional_copy_assign_base() = default;
optional_copy_assign_base(const optional_copy_assign_base &rhs) = default;
optional_copy_assign_base(optional_copy_assign_base &&rhs) = default;
optional_copy_assign_base &operator=(const optional_copy_assign_base &rhs) {
this->assign(rhs);
return *this;
}
optional_copy_assign_base &
operator=(optional_copy_assign_base &&rhs) = default;
};
// This class manages conditionally having a trivial move assignment operator
// Unfortunately there's no way to achieve this in GCC < 5 AFAIK, since it
// doesn't implement an analogue to std::is_trivially_move_assignable. We have
// to make do with a non-trivial move assignment operator even if T is trivially
// move assignable
#ifndef TL_OPTIONAL_GCC49
template <class T, bool = std::is_trivially_destructible<T>::value
&&std::is_trivially_move_constructible<T>::value
&&std::is_trivially_move_assignable<T>::value>
struct optional_move_assign_base : optional_copy_assign_base<T> {
using optional_copy_assign_base<T>::optional_copy_assign_base;
};
#else
template <class T, bool = false> struct optional_move_assign_base;
#endif
template <class T>
struct optional_move_assign_base<T, false> : optional_copy_assign_base<T> {
using optional_copy_assign_base<T>::optional_copy_assign_base;
optional_move_assign_base() = default;
optional_move_assign_base(const optional_move_assign_base &rhs) = default;
optional_move_assign_base(optional_move_assign_base &&rhs) = default;
optional_move_assign_base &
operator=(const optional_move_assign_base &rhs) = default;
optional_move_assign_base &
operator=(optional_move_assign_base &&rhs) noexcept(
std::is_nothrow_move_constructible<T>::value
&&std::is_nothrow_move_assignable<T>::value) {
this->assign(std::move(rhs));
return *this;
}
};
// optional_delete_ctor_base will conditionally delete copy and move
// constructors depending on whether T is copy/move constructible
template <class T, bool EnableCopy = std::is_copy_constructible<T>::value,
bool EnableMove = std::is_move_constructible<T>::value>
struct optional_delete_ctor_base {
optional_delete_ctor_base() = default;
optional_delete_ctor_base(const optional_delete_ctor_base &) = default;
optional_delete_ctor_base(optional_delete_ctor_base &&) noexcept = default;
optional_delete_ctor_base &
operator=(const optional_delete_ctor_base &) = default;
optional_delete_ctor_base &
operator=(optional_delete_ctor_base &&) noexcept = default;
};
template <class T> struct optional_delete_ctor_base<T, true, false> {
optional_delete_ctor_base() = default;
optional_delete_ctor_base(const optional_delete_ctor_base &) = default;
optional_delete_ctor_base(optional_delete_ctor_base &&) noexcept = delete;
optional_delete_ctor_base &
operator=(const optional_delete_ctor_base &) = default;
optional_delete_ctor_base &
operator=(optional_delete_ctor_base &&) noexcept = default;
};
template <class T> struct optional_delete_ctor_base<T, false, true> {
optional_delete_ctor_base() = default;
optional_delete_ctor_base(const optional_delete_ctor_base &) = delete;
optional_delete_ctor_base(optional_delete_ctor_base &&) noexcept = default;
optional_delete_ctor_base &
operator=(const optional_delete_ctor_base &) = default;
optional_delete_ctor_base &
operator=(optional_delete_ctor_base &&) noexcept = default;
};
template <class T> struct optional_delete_ctor_base<T, false, false> {
optional_delete_ctor_base() = default;
optional_delete_ctor_base(const optional_delete_ctor_base &) = delete;
optional_delete_ctor_base(optional_delete_ctor_base &&) noexcept = delete;
optional_delete_ctor_base &
operator=(const optional_delete_ctor_base &) = default;
optional_delete_ctor_base &
operator=(optional_delete_ctor_base &&) noexcept = default;
};
// optional_delete_assign_base will conditionally delete copy and move
// constructors depending on whether T is copy/move constructible + assignable
template <class T,
bool EnableCopy = (std::is_copy_constructible<T>::value &&
std::is_copy_assignable<T>::value),
bool EnableMove = (std::is_move_constructible<T>::value &&
std::is_move_assignable<T>::value)>
struct optional_delete_assign_base {
optional_delete_assign_base() = default;
optional_delete_assign_base(const optional_delete_assign_base &) = default;
optional_delete_assign_base(optional_delete_assign_base &&) noexcept =
default;
optional_delete_assign_base &
operator=(const optional_delete_assign_base &) = default;
optional_delete_assign_base &
operator=(optional_delete_assign_base &&) noexcept = default;
};
template <class T> struct optional_delete_assign_base<T, true, false> {
optional_delete_assign_base() = default;
optional_delete_assign_base(const optional_delete_assign_base &) = default;
optional_delete_assign_base(optional_delete_assign_base &&) noexcept =
default;
optional_delete_assign_base &
operator=(const optional_delete_assign_base &) = default;
optional_delete_assign_base &
operator=(optional_delete_assign_base &&) noexcept = delete;
};
template <class T> struct optional_delete_assign_base<T, false, true> {
optional_delete_assign_base() = default;
optional_delete_assign_base(const optional_delete_assign_base &) = default;
optional_delete_assign_base(optional_delete_assign_base &&) noexcept =
default;
optional_delete_assign_base &
operator=(const optional_delete_assign_base &) = delete;
optional_delete_assign_base &
operator=(optional_delete_assign_base &&) noexcept = default;
};
template <class T> struct optional_delete_assign_base<T, false, false> {
optional_delete_assign_base() = default;
optional_delete_assign_base(const optional_delete_assign_base &) = default;
optional_delete_assign_base(optional_delete_assign_base &&) noexcept =
default;
optional_delete_assign_base &
operator=(const optional_delete_assign_base &) = delete;
optional_delete_assign_base &
operator=(optional_delete_assign_base &&) noexcept = delete;
};
} // namespace detail
/// \brief A tag type to represent an empty optional
struct nullopt_t {
struct do_not_use {};
constexpr explicit nullopt_t(do_not_use, do_not_use) noexcept {}
};
/// \brief Represents an empty optional
/// \synopsis static constexpr nullopt_t nullopt;
///
/// *Examples*:
/// ```
/// tl::optional<int> a = tl::nullopt;
/// void foo (tl::optional<int>);
/// foo(tl::nullopt); //pass an empty optional
/// ```
static constexpr nullopt_t nullopt{nullopt_t::do_not_use{},
nullopt_t::do_not_use{}};
class bad_optional_access : public std::exception {
public:
bad_optional_access() = default;
const char *what() const noexcept { return "Optional has no value"; }
};
/// An optional object is an object that contains the storage for another
/// object and manages the lifetime of this contained object, if any. The
/// contained object may be initialized after the optional object has been
/// initialized, and may be destroyed before the optional object has been
/// destroyed. The initialization state of the contained object is tracked by
/// the optional object.
template <class T>
class optional : private detail::optional_move_assign_base<T>,
private detail::optional_delete_ctor_base<T>,
private detail::optional_delete_assign_base<T> {
using base = detail::optional_move_assign_base<T>;
static_assert(!std::is_same<T, in_place_t>::value,
"instantiation of optional with in_place_t is ill-formed");
static_assert(!std::is_same<detail::decay_t<T>, nullopt_t>::value,
"instantiation of optional with nullopt_t is ill-formed");
public:
// The different versions for C++14 and 11 are needed because deduced return
// types are not SFINAE-safe. This provides better support for things like
// generic lambdas. C.f.
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0826r0.html
#if defined(TL_OPTIONAL_CXX14) && !defined(TL_OPTIONAL_GCC49) && \
!defined(TL_OPTIONAL_GCC54) && !defined(TL_OPTIONAL_GCC55)
/// \group and_then
/// Carries out some operation which returns an optional on the stored
/// object if there is one. \requires `std::invoke(std::forward<F>(f),
/// value())` returns a `std::optional<U>` for some `U`. \returns Let `U` be
/// the result of `std::invoke(std::forward<F>(f), value())`. Returns a
/// `std::optional<U>`. The return value is empty if `*this` is empty,
/// otherwise the return value of `std::invoke(std::forward<F>(f), value())`
/// is returned.
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) &;
template <class F> TL_OPTIONAL_11_CONSTEXPR auto and_then(F &&f) & {
using result = detail::invoke_result_t<F, T &>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: result(nullopt);
}
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) &&;
template <class F> TL_OPTIONAL_11_CONSTEXPR auto and_then(F &&f) && {
using result = detail::invoke_result_t<F, T &&>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), std::move(**this))
: result(nullopt);
}
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) const &;
template <class F> constexpr auto and_then(F &&f) const & {
using result = detail::invoke_result_t<F, const T &>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: result(nullopt);
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) const &&;
template <class F> constexpr auto and_then(F &&f) const && {
using result = detail::invoke_result_t<F, const T &&>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), std::move(**this))
: result(nullopt);
}
#endif
#else
/// \group and_then
/// Carries out some operation which returns an optional on the stored
/// object if there is one. \requires `std::invoke(std::forward<F>(f),
/// value())` returns a `std::optional<U>` for some `U`.
/// \returns Let `U` be the result of `std::invoke(std::forward<F>(f),
/// value())`. Returns a `std::optional<U>`. The return value is empty if
/// `*this` is empty, otherwise the return value of
/// `std::invoke(std::forward<F>(f), value())` is returned.
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) &;
template <class F>
TL_OPTIONAL_11_CONSTEXPR detail::invoke_result_t<F, T &> and_then(F &&f) & {
using result = detail::invoke_result_t<F, T &>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: result(nullopt);
}
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) &&;
template <class F>
TL_OPTIONAL_11_CONSTEXPR detail::invoke_result_t<F, T &&> and_then(F &&f) && {
using result = detail::invoke_result_t<F, T &&>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), std::move(**this))
: result(nullopt);
}
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) const &;
template <class F>
constexpr detail::invoke_result_t<F, const T &> and_then(F &&f) const & {
using result = detail::invoke_result_t<F, const T &>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: result(nullopt);
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) const &&;
template <class F>
constexpr detail::invoke_result_t<F, const T &&> and_then(F &&f) const && {
using result = detail::invoke_result_t<F, const T &&>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), std::move(**this))
: result(nullopt);
}
#endif
#endif
#if defined(TL_OPTIONAL_CXX14) && !defined(TL_OPTIONAL_GCC49) && \
!defined(TL_OPTIONAL_GCC54) && !defined(TL_OPTIONAL_GCC55)
/// \brief Carries out some operation on the stored object if there is one.
/// \returns Let `U` be the result of `std::invoke(std::forward<F>(f),
/// value())`. Returns a `std::optional<U>`. The return value is empty if
/// `*this` is empty, otherwise an `optional<U>` is constructed from the
/// return value of `std::invoke(std::forward<F>(f), value())` and is
/// returned.
///
/// \group map
/// \synopsis template <class F> constexpr auto map(F &&f) &;
template <class F> TL_OPTIONAL_11_CONSTEXPR auto map(F &&f) & {
return optional_map_impl(*this, std::forward<F>(f));
}
/// \group map
/// \synopsis template <class F> constexpr auto map(F &&f) &&;
template <class F> TL_OPTIONAL_11_CONSTEXPR auto map(F &&f) && {
return optional_map_impl(std::move(*this), std::forward<F>(f));
}
/// \group map
/// \synopsis template <class F> constexpr auto map(F &&f) const&;
template <class F> constexpr auto map(F &&f) const & {
return optional_map_impl(*this, std::forward<F>(f));
}
/// \group map
/// \synopsis template <class F> constexpr auto map(F &&f) const&&;
template <class F> constexpr auto map(F &&f) const && {
return optional_map_impl(std::move(*this), std::forward<F>(f));
}
#else
/// \brief Carries out some operation on the stored object if there is one.
/// \returns Let `U` be the result of `std::invoke(std::forward<F>(f),
/// value())`. Returns a `std::optional<U>`. The return value is empty if
/// `*this` is empty, otherwise an `optional<U>` is constructed from the
/// return value of `std::invoke(std::forward<F>(f), value())` and is
/// returned.
///
/// \group map
/// \synopsis template <class F> auto map(F &&f) &;
template <class F>
TL_OPTIONAL_11_CONSTEXPR decltype(optional_map_impl(std::declval<optional &>(),
std::declval<F &&>()))
map(F &&f) & {
return optional_map_impl(*this, std::forward<F>(f));
}
/// \group map
/// \synopsis template <class F> auto map(F &&f) &&;
template <class F>
TL_OPTIONAL_11_CONSTEXPR decltype(optional_map_impl(std::declval<optional &&>(),
std::declval<F &&>()))
map(F &&f) && {
return optional_map_impl(std::move(*this), std::forward<F>(f));
}
/// \group map
/// \synopsis template <class F> auto map(F &&f) const&;
template <class F>
constexpr decltype(optional_map_impl(std::declval<const optional &>(),
std::declval<F &&>()))
map(F &&f) const & {
return optional_map_impl(*this, std::forward<F>(f));
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group map
/// \synopsis template <class F> auto map(F &&f) const&&;
template <class F>
constexpr decltype(optional_map_impl(std::declval<const optional &&>(),
std::declval<F &&>()))
map(F &&f) const && {
return optional_map_impl(std::move(*this), std::forward<F>(f));
}
#endif
#endif
/// \brief Calls `f` if the optional is empty
/// \requires `std::invoke_result_t<F>` must be void or convertible to
/// `optional<T>`.
/// \effects If `*this` has a value, returns `*this`.
/// Otherwise, if `f` returns `void`, calls `std::forward<F>(f)` and returns
/// `std::nullopt`. Otherwise, returns `std::forward<F>(f)()`.
///
/// \group or_else
/// \synopsis template <class F> optional<T> or_else (F &&f) &;
template <class F, detail::enable_if_ret_void<F> * = nullptr>
optional<T> TL_OPTIONAL_11_CONSTEXPR or_else(F &&f) & {
if (has_value())
return *this;
std::forward<F>(f)();
return nullopt;
}
/// \exclude
template <class F, detail::disable_if_ret_void<F> * = nullptr>
optional<T> TL_OPTIONAL_11_CONSTEXPR or_else(F &&f) & {
return has_value() ? *this : std::forward<F>(f)();
}
/// \group or_else
/// \synopsis template <class F> optional<T> or_else (F &&f) &&;
template <class F, detail::enable_if_ret_void<F> * = nullptr>
optional<T> or_else(F &&f) && {
if (has_value())
return std::move(*this);
std::forward<F>(f)();
return nullopt;
}
/// \exclude
template <class F, detail::disable_if_ret_void<F> * = nullptr>
optional<T> TL_OPTIONAL_11_CONSTEXPR or_else(F &&f) && {
return has_value() ? std::move(*this) : std::forward<F>(f)();
}
/// \group or_else
/// \synopsis template <class F> optional<T> or_else (F &&f) const &;
template <class F, detail::enable_if_ret_void<F> * = nullptr>
optional<T> or_else(F &&f) const & {
if (has_value())
return *this;
std::forward<F>(f)();
return nullopt;
}
/// \exclude
template <class F, detail::disable_if_ret_void<F> * = nullptr>
optional<T> TL_OPTIONAL_11_CONSTEXPR or_else(F &&f) const & {
return has_value() ? *this : std::forward<F>(f)();
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \exclude
template <class F, detail::enable_if_ret_void<F> * = nullptr>
optional<T> or_else(F &&f) const && {
if (has_value())
return std::move(*this);
std::forward<F>(f)();
return nullopt;
}
/// \exclude
template <class F, detail::disable_if_ret_void<F> * = nullptr>
optional<T> or_else(F &&f) const && {
return has_value() ? std::move(*this) : std::forward<F>(f)();
}
#endif
/// \brief Maps the stored value with `f` if there is one, otherwise returns
/// `u`.
///
/// \details If there is a value stored, then `f` is called with `**this`
/// and the value is returned. Otherwise `u` is returned.
///
/// \group map_or
template <class F, class U> U map_or(F &&f, U &&u) & {
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: std::forward<U>(u);
}
/// \group map_or
template <class F, class U> U map_or(F &&f, U &&u) && {
return has_value() ? detail::invoke(std::forward<F>(f), std::move(**this))
: std::forward<U>(u);
}
/// \group map_or
template <class F, class U> U map_or(F &&f, U &&u) const & {
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: std::forward<U>(u);
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group map_or
template <class F, class U> U map_or(F &&f, U &&u) const && {
return has_value() ? detail::invoke(std::forward<F>(f), std::move(**this))
: std::forward<U>(u);
}
#endif
/// \brief Maps the stored value with `f` if there is one, otherwise calls
/// `u` and returns the result.
///
/// \details If there is a value stored, then `f` is
/// called with `**this` and the value is returned. Otherwise
/// `std::forward<U>(u)()` is returned.
///
/// \group map_or_else
/// \synopsis template <class F, class U>\nauto map_or_else(F &&f, U &&u) &;
template <class F, class U>
detail::invoke_result_t<U> map_or_else(F &&f, U &&u) & {
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: std::forward<U>(u)();
}
/// \group map_or_else
/// \synopsis template <class F, class U>\nauto map_or_else(F &&f, U &&u)
/// &&;
template <class F, class U>
detail::invoke_result_t<U> map_or_else(F &&f, U &&u) && {
return has_value() ? detail::invoke(std::forward<F>(f), std::move(**this))
: std::forward<U>(u)();
}
/// \group map_or_else
/// \synopsis template <class F, class U>\nauto map_or_else(F &&f, U &&u)
/// const &;
template <class F, class U>
detail::invoke_result_t<U> map_or_else(F &&f, U &&u) const & {
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: std::forward<U>(u)();
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group map_or_else
/// \synopsis template <class F, class U>\nauto map_or_else(F &&f, U &&u)
/// const &&;
template <class F, class U>
detail::invoke_result_t<U> map_or_else(F &&f, U &&u) const && {
return has_value() ? detail::invoke(std::forward<F>(f), std::move(**this))
: std::forward<U>(u)();
}
#endif
/// \returns `u` if `*this` has a value, otherwise an empty optional.
template <class U>
constexpr optional<typename std::decay<U>::type> conjunction(U &&u) const {
using result = optional<detail::decay_t<U>>;
return has_value() ? result{u} : result{nullopt};
}
/// \returns `rhs` if `*this` is empty, otherwise the current value.
/// \group disjunction
TL_OPTIONAL_11_CONSTEXPR optional disjunction(const optional &rhs) & {
return has_value() ? *this : rhs;
}
/// \group disjunction
constexpr optional disjunction(const optional &rhs) const & {
return has_value() ? *this : rhs;
}
/// \group disjunction
TL_OPTIONAL_11_CONSTEXPR optional disjunction(const optional &rhs) && {
return has_value() ? std::move(*this) : rhs;
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group disjunction
constexpr optional disjunction(const optional &rhs) const && {
return has_value() ? std::move(*this) : rhs;
}
#endif
/// \group disjunction
TL_OPTIONAL_11_CONSTEXPR optional disjunction(optional &&rhs) & {
return has_value() ? *this : std::move(rhs);
}
/// \group disjunction
constexpr optional disjunction(optional &&rhs) const & {
return has_value() ? *this : std::move(rhs);
}
/// \group disjunction
TL_OPTIONAL_11_CONSTEXPR optional disjunction(optional &&rhs) && {
return has_value() ? std::move(*this) : std::move(rhs);
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group disjunction
constexpr optional disjunction(optional &&rhs) const && {
return has_value() ? std::move(*this) : std::move(rhs);
}
#endif
/// Takes the value out of the optional, leaving it empty
/// \group take
optional take() & {
optional ret = *this;
reset();
return ret;
}
/// \group take
optional take() const & {
optional ret = *this;
reset();
return ret;
}
/// \group take
optional take() && {
optional ret = std::move(*this);
reset();
return ret;
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group take
optional take() const && {
optional ret = std::move(*this);
reset();
return ret;
}
#endif
using value_type = T;
/// Constructs an optional that does not contain a value.
/// \group ctor_empty
constexpr optional() noexcept = default;
/// \group ctor_empty
constexpr optional(nullopt_t) noexcept {}
/// Copy constructor
///
/// If `rhs` contains a value, the stored value is direct-initialized with
/// it. Otherwise, the constructed optional is empty.
TL_OPTIONAL_11_CONSTEXPR optional(const optional &rhs) = default;
/// Move constructor
///
/// If `rhs` contains a value, the stored value is direct-initialized with
/// it. Otherwise, the constructed optional is empty.
TL_OPTIONAL_11_CONSTEXPR optional(optional &&rhs) = default;
/// Constructs the stored value in-place using the given arguments.
/// \group in_place
/// \synopsis template <class... Args> constexpr explicit optional(in_place_t, Args&&... args);
template <class... Args>
constexpr explicit optional(
detail::enable_if_t<std::is_constructible<T, Args...>::value, in_place_t>,
Args &&... args)
: base(in_place, std::forward<Args>(args)...) {}
/// \group in_place
/// \synopsis template <class U, class... Args>\nconstexpr explicit optional(in_place_t, std::initializer_list<U>&, Args&&... args);
template <class U, class... Args>
TL_OPTIONAL_11_CONSTEXPR explicit optional(
detail::enable_if_t<std::is_constructible<T, std::initializer_list<U> &,
Args &&...>::value,
in_place_t>,
std::initializer_list<U> il, Args &&... args) {
this->construct(il, std::forward<Args>(args)...);
}
/// Constructs the stored value with `u`.
/// \synopsis template <class U=T> constexpr optional(U &&u);
template <
class U = T,
detail::enable_if_t<std::is_convertible<U &&, T>::value> * = nullptr,
detail::enable_forward_value<T, U> * = nullptr>
constexpr optional(U &&u) : base(in_place, std::forward<U>(u)) {}
/// \exclude
template <
class U = T,
detail::enable_if_t<!std::is_convertible<U &&, T>::value> * = nullptr,
detail::enable_forward_value<T, U> * = nullptr>
constexpr explicit optional(U &&u) : base(in_place, std::forward<U>(u)) {}
/// Converting copy constructor.
/// \synopsis template <class U> optional(const optional<U> &rhs);
template <
class U, detail::enable_from_other<T, U, const U &> * = nullptr,
detail::enable_if_t<std::is_convertible<const U &, T>::value> * = nullptr>
optional(const optional<U> &rhs) {
this->construct(*rhs);
}
/// \exclude
template <class U, detail::enable_from_other<T, U, const U &> * = nullptr,
detail::enable_if_t<!std::is_convertible<const U &, T>::value> * =
nullptr>
explicit optional(const optional<U> &rhs) {
this->construct(*rhs);
}
/// Converting move constructor.
/// \synopsis template <class U> optional(optional<U> &&rhs);
template <
class U, detail::enable_from_other<T, U, U &&> * = nullptr,
detail::enable_if_t<std::is_convertible<U &&, T>::value> * = nullptr>
optional(optional<U> &&rhs) {
this->construct(std::move(*rhs));
}
/// \exclude
template <
class U, detail::enable_from_other<T, U, U &&> * = nullptr,
detail::enable_if_t<!std::is_convertible<U &&, T>::value> * = nullptr>
explicit optional(optional<U> &&rhs) {
this->construct(std::move(*rhs));
}
/// Destroys the stored value if there is one.
~optional() = default;
/// Assignment to empty.
///
/// Destroys the current value if there is one.
optional &operator=(nullopt_t) noexcept {
if (has_value()) {
this->m_value.~T();
this->m_has_value = false;
}
return *this;
}
/// Copy assignment.
///
/// Copies the value from `rhs` if there is one. Otherwise resets the stored
/// value in `*this`.
optional &operator=(const optional &rhs) = default;
/// Move assignment.
///
/// Moves the value from `rhs` if there is one. Otherwise resets the stored
/// value in `*this`.
optional &operator=(optional &&rhs) = default;
/// Assigns the stored value from `u`, destroying the old value if there was
/// one.
/// \synopsis optional &operator=(U &&u);
template <class U = T, detail::enable_assign_forward<T, U> * = nullptr>
optional &operator=(U &&u) {
if (has_value()) {
this->m_value = std::forward<U>(u);
} else {
this->construct(std::forward<U>(u));
}
return *this;
}
/// Converting copy assignment operator.
///
/// Copies the value from `rhs` if there is one. Otherwise resets the stored
/// value in `*this`.
/// \synopsis optional &operator=(const optional<U> & rhs);
template <class U,
detail::enable_assign_from_other<T, U, const U &> * = nullptr>
optional &operator=(const optional<U> &rhs) {
if (has_value()) {
if (rhs.has_value()) {
this->m_value = *rhs;
} else {
this->hard_reset();
}
}
if (rhs.has_value()) {
this->construct(*rhs);
}
return *this;
}
// TODO check exception guarantee
/// Converting move assignment operator.
///
/// Moves the value from `rhs` if there is one. Otherwise resets the stored
/// value in `*this`.
/// \synopsis optional &operator=(optional<U> && rhs);
template <class U, detail::enable_assign_from_other<T, U, U> * = nullptr>
optional &operator=(optional<U> &&rhs) {
if (has_value()) {
if (rhs.has_value()) {
this->m_value = std::move(*rhs);
} else {
this->hard_reset();
}
}
if (rhs.has_value()) {
this->construct(std::move(*rhs));
}
return *this;
}
/// Constructs the value in-place, destroying the current one if there is
/// one.
/// \group emplace
template <class... Args> T &emplace(Args &&... args) {
static_assert(std::is_constructible<T, Args &&...>::value,
"T must be constructible with Args");
*this = nullopt;
this->construct(std::forward<Args>(args)...);
return value();
}
/// \group emplace
/// \synopsis template <class U, class... Args>\nT& emplace(std::initializer_list<U> il, Args &&... args);
template <class U, class... Args>
detail::enable_if_t<
std::is_constructible<T, std::initializer_list<U> &, Args &&...>::value,
T &>
emplace(std::initializer_list<U> il, Args &&... args) {
*this = nullopt;
this->construct(il, std::forward<Args>(args)...);
return value();
}
/// Swaps this optional with the other.
///
/// If neither optionals have a value, nothing happens.
/// If both have a value, the values are swapped.
/// If one has a value, it is moved to the other and the movee is left
/// valueless.
void
swap(optional &rhs) noexcept(std::is_nothrow_move_constructible<T>::value
&&detail::is_nothrow_swappable<T>::value) {
if (has_value()) {
if (rhs.has_value()) {
using std::swap;
swap(**this, *rhs);
} else {
new (std::addressof(rhs.m_value)) T(std::move(this->m_value));
this->m_value.T::~T();
}
} else if (rhs.has_value()) {
new (std::addressof(this->m_value)) T(std::move(rhs.m_value));
rhs.m_value.T::~T();
}
}
/// \returns a pointer to the stored value
/// \requires a value is stored
/// \group pointer
/// \synopsis constexpr const T *operator->() const;
constexpr const T *operator->() const {
return std::addressof(this->m_value);
}
/// \group pointer
/// \synopsis constexpr T *operator->();
TL_OPTIONAL_11_CONSTEXPR T *operator->() {
return std::addressof(this->m_value);
}
/// \returns the stored value
/// \requires a value is stored
/// \group deref
/// \synopsis constexpr T &operator*();
TL_OPTIONAL_11_CONSTEXPR T &operator*() & { return this->m_value; }
/// \group deref
/// \synopsis constexpr const T &operator*() const;
constexpr const T &operator*() const & { return this->m_value; }
/// \exclude
TL_OPTIONAL_11_CONSTEXPR T &&operator*() && {
return std::move(this->m_value);
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \exclude
constexpr const T &&operator*() const && { return std::move(this->m_value); }
#endif
/// \returns whether or not the optional has a value
/// \group has_value
constexpr bool has_value() const noexcept { return this->m_has_value; }
/// \group has_value
constexpr explicit operator bool() const noexcept {
return this->m_has_value;
}
/// \returns the contained value if there is one, otherwise throws
/// [bad_optional_access]
/// \group value
/// \synopsis constexpr T &value();
TL_OPTIONAL_11_CONSTEXPR T &value() & {
if (has_value())
return this->m_value;
throw bad_optional_access();
}
/// \group value
/// \synopsis constexpr const T &value() const;
TL_OPTIONAL_11_CONSTEXPR const T &value() const & {
if (has_value())
return this->m_value;
throw bad_optional_access();
}
/// \exclude
TL_OPTIONAL_11_CONSTEXPR T &&value() && {
if (has_value())
return std::move(this->m_value);
throw bad_optional_access();
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \exclude
TL_OPTIONAL_11_CONSTEXPR const T &&value() const && {
if (has_value())
return std::move(this->m_value);
throw bad_optional_access();
}
#endif
/// \returns the stored value if there is one, otherwise returns `u`
/// \group value_or
template <class U> constexpr T value_or(U &&u) const & {
static_assert(std::is_copy_constructible<T>::value &&
std::is_convertible<U &&, T>::value,
"T must be copy constructible and convertible from U");
return has_value() ? **this : static_cast<T>(std::forward<U>(u));
}
/// \group value_or
template <class U> TL_OPTIONAL_11_CONSTEXPR T value_or(U &&u) && {
static_assert(std::is_move_constructible<T>::value &&
std::is_convertible<U &&, T>::value,
"T must be move constructible and convertible from U");
return has_value() ? **this : static_cast<T>(std::forward<U>(u));
}
/// Destroys the stored value if one exists, making the optional empty
void reset() noexcept {
if (has_value()) {
this->m_value.~T();
this->m_has_value = false;
}
}
}; // namespace tl
/// \group relop
/// \brief Compares two optional objects
/// \details If both optionals contain a value, they are compared with `T`s
/// relational operators. Otherwise `lhs` and `rhs` are equal only if they are
/// both empty, and `lhs` is less than `rhs` only if `rhs` is empty and `lhs`
/// is not.
template <class T, class U>
inline constexpr bool operator==(const optional<T> &lhs,
const optional<U> &rhs) {
return lhs.has_value() == rhs.has_value() &&
(!lhs.has_value() || *lhs == *rhs);
}
/// \group relop
template <class T, class U>
inline constexpr bool operator!=(const optional<T> &lhs,
const optional<U> &rhs) {
return lhs.has_value() != rhs.has_value() ||
(lhs.has_value() && *lhs != *rhs);
}
/// \group relop
template <class T, class U>
inline constexpr bool operator<(const optional<T> &lhs,
const optional<U> &rhs) {
return rhs.has_value() && (!lhs.has_value() || *lhs < *rhs);
}
/// \group relop
template <class T, class U>
inline constexpr bool operator>(const optional<T> &lhs,
const optional<U> &rhs) {
return lhs.has_value() && (!rhs.has_value() || *lhs > *rhs);
}
/// \group relop
template <class T, class U>
inline constexpr bool operator<=(const optional<T> &lhs,
const optional<U> &rhs) {
return !lhs.has_value() || (rhs.has_value() && *lhs <= *rhs);
}
/// \group relop
template <class T, class U>
inline constexpr bool operator>=(const optional<T> &lhs,
const optional<U> &rhs) {
return !rhs.has_value() || (lhs.has_value() && *lhs >= *rhs);
}
/// \group relop_nullopt
/// \brief Compares an optional to a `nullopt`
/// \details Equivalent to comparing the optional to an empty optional
template <class T>
inline constexpr bool operator==(const optional<T> &lhs, nullopt_t) noexcept {
return !lhs.has_value();
}
/// \group relop_nullopt
template <class T>
inline constexpr bool operator==(nullopt_t, const optional<T> &rhs) noexcept {
return !rhs.has_value();
}
/// \group relop_nullopt
template <class T>
inline constexpr bool operator!=(const optional<T> &lhs, nullopt_t) noexcept {
return lhs.has_value();
}
/// \group relop_nullopt
template <class T>
inline constexpr bool operator!=(nullopt_t, const optional<T> &rhs) noexcept {
return rhs.has_value();
}
/// \group relop_nullopt
template <class T>
inline constexpr bool operator<(const optional<T> &, nullopt_t) noexcept {
return false;
}
/// \group relop_nullopt
template <class T>
inline constexpr bool operator<(nullopt_t, const optional<T> &rhs) noexcept {
return rhs.has_value();
}
/// \group relop_nullopt
template <class T>
inline constexpr bool operator<=(const optional<T> &lhs, nullopt_t) noexcept {
return !lhs.has_value();
}
/// \group relop_nullopt
template <class T>
inline constexpr bool operator<=(nullopt_t, const optional<T> &) noexcept {
return true;
}
/// \group relop_nullopt
template <class T>
inline constexpr bool operator>(const optional<T> &lhs, nullopt_t) noexcept {
return lhs.has_value();
}
/// \group relop_nullopt
template <class T>
inline constexpr bool operator>(nullopt_t, const optional<T> &) noexcept {
return false;
}
/// \group relop_nullopt
template <class T>
inline constexpr bool operator>=(const optional<T> &, nullopt_t) noexcept {
return true;
}
/// \group relop_nullopt
template <class T>
inline constexpr bool operator>=(nullopt_t, const optional<T> &rhs) noexcept {
return !rhs.has_value();
}
/// \group relop_t
/// \brief Compares the optional with a value.
/// \details If the optional has a value, it is compared with the other value
/// using `T`s relational operators. Otherwise, the optional is considered
/// less than the value.
template <class T, class U>
inline constexpr bool operator==(const optional<T> &lhs, const U &rhs) {
return lhs.has_value() ? *lhs == rhs : false;
}
/// \group relop_t
template <class T, class U>
inline constexpr bool operator==(const U &lhs, const optional<T> &rhs) {
return rhs.has_value() ? lhs == *rhs : false;
}
/// \group relop_t
template <class T, class U>
inline constexpr bool operator!=(const optional<T> &lhs, const U &rhs) {
return lhs.has_value() ? *lhs != rhs : true;
}
/// \group relop_t
template <class T, class U>
inline constexpr bool operator!=(const U &lhs, const optional<T> &rhs) {
return rhs.has_value() ? lhs != *rhs : true;
}
/// \group relop_t
template <class T, class U>
inline constexpr bool operator<(const optional<T> &lhs, const U &rhs) {
return lhs.has_value() ? *lhs < rhs : true;
}
/// \group relop_t
template <class T, class U>
inline constexpr bool operator<(const U &lhs, const optional<T> &rhs) {
return rhs.has_value() ? lhs < *rhs : false;
}
/// \group relop_t
template <class T, class U>
inline constexpr bool operator<=(const optional<T> &lhs, const U &rhs) {
return lhs.has_value() ? *lhs <= rhs : true;
}
/// \group relop_t
template <class T, class U>
inline constexpr bool operator<=(const U &lhs, const optional<T> &rhs) {
return rhs.has_value() ? lhs <= *rhs : false;
}
/// \group relop_t
template <class T, class U>
inline constexpr bool operator>(const optional<T> &lhs, const U &rhs) {
return lhs.has_value() ? *lhs > rhs : false;
}
/// \group relop_t
template <class T, class U>
inline constexpr bool operator>(const U &lhs, const optional<T> &rhs) {
return rhs.has_value() ? lhs > *rhs : true;
}
/// \group relop_t
template <class T, class U>
inline constexpr bool operator>=(const optional<T> &lhs, const U &rhs) {
return lhs.has_value() ? *lhs >= rhs : false;
}
/// \group relop_t
template <class T, class U>
inline constexpr bool operator>=(const U &lhs, const optional<T> &rhs) {
return rhs.has_value() ? lhs >= *rhs : true;
}
/// \synopsis template <class T>\nvoid swap(optional<T> &lhs, optional<T> &rhs);
template <class T,
detail::enable_if_t<std::is_move_constructible<T>::value> * = nullptr,
detail::enable_if_t<detail::is_swappable<T>::value> * = nullptr>
void swap(optional<T> &lhs,
optional<T> &rhs) noexcept(noexcept(lhs.swap(rhs))) {
return lhs.swap(rhs);
}
namespace detail {
struct i_am_secret {};
} // namespace detail
template <class T = detail::i_am_secret, class U,
class Ret =
detail::conditional_t<std::is_same<T, detail::i_am_secret>::value,
detail::decay_t<U>, T>>
inline constexpr optional<Ret> make_optional(U &&v) {
return optional<Ret>(std::forward<U>(v));
}
template <class T, class... Args>
inline constexpr optional<T> make_optional(Args &&... args) {
return optional<T>(in_place, std::forward<Args>(args)...);
}
template <class T, class U, class... Args>
inline constexpr optional<T> make_optional(std::initializer_list<U> il,
Args &&... args) {
return optional<T>(in_place, il, std::forward<Args>(args)...);
}
#if __cplusplus >= 201703L
template <class T> optional(T)->optional<T>;
#endif
/// \exclude
namespace detail {
#ifdef TL_OPTIONAL_CXX14
template <class Opt, class F,
class Ret = decltype(detail::invoke(std::declval<F>(),
*std::declval<Opt>())),
detail::enable_if_t<!std::is_void<Ret>::value> * = nullptr>
constexpr auto optional_map_impl(Opt &&opt, F &&f) {
return opt.has_value()
? detail::invoke(std::forward<F>(f), *std::forward<Opt>(opt))
: optional<Ret>(nullopt);
}
template <class Opt, class F,
class Ret = decltype(detail::invoke(std::declval<F>(),
*std::declval<Opt>())),
detail::enable_if_t<std::is_void<Ret>::value> * = nullptr>
auto optional_map_impl(Opt &&opt, F &&f) {
if (opt.has_value()) {
detail::invoke(std::forward<F>(f), *std::forward<Opt>(opt));
return make_optional(monostate{});
}
return optional<monostate>(nullopt);
}
#else
template <class Opt, class F,
class Ret = decltype(detail::invoke(std::declval<F>(),
*std::declval<Opt>())),
detail::enable_if_t<!std::is_void<Ret>::value> * = nullptr>
constexpr auto optional_map_impl(Opt &&opt, F &&f) -> optional<Ret> {
return opt.has_value()
? detail::invoke(std::forward<F>(f), *std::forward<Opt>(opt))
: optional<Ret>(nullopt);
}
template <class Opt, class F,
class Ret = decltype(detail::invoke(std::declval<F>(),
*std::declval<Opt>())),
detail::enable_if_t<std::is_void<Ret>::value> * = nullptr>
auto optional_map_impl(Opt &&opt, F &&f) -> optional<monostate> {
if (opt.has_value()) {
detail::invoke(std::forward<F>(f), *std::forward<Opt>(opt));
return monostate{};
}
return nullopt;
}
#endif
} // namespace detail
/// Specialization for when `T` is a reference. `optional<T&>` acts similarly
/// to a `T*`, but provides more operations and shows intent more clearly.
///
/// *Examples*:
///
/// ```
/// int i = 42;
/// tl::optional<int&> o = i;
/// *o == 42; //true
/// i = 12;
/// *o = 12; //true
/// &*o == &i; //true
/// ```
///
/// Assignment has rebind semantics rather than assign-through semantics:
///
/// ```
/// int j = 8;
/// o = j;
///
/// &*o == &j; //true
/// ```
template <class T> class optional<T &> {
public:
// The different versions for C++14 and 11 are needed because deduced return
// types are not SFINAE-safe. This provides better support for things like
// generic lambdas. C.f.
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0826r0.html
#if defined(TL_OPTIONAL_CXX14) && !defined(TL_OPTIONAL_GCC49) && \
!defined(TL_OPTIONAL_GCC54) && !defined(TL_OPTIONAL_GCC55)
/// \group and_then
/// Carries out some operation which returns an optional on the stored
/// object if there is one. \requires `std::invoke(std::forward<F>(f),
/// value())` returns a `std::optional<U>` for some `U`. \returns Let `U` be
/// the result of `std::invoke(std::forward<F>(f), value())`. Returns a
/// `std::optional<U>`. The return value is empty if `*this` is empty,
/// otherwise the return value of `std::invoke(std::forward<F>(f), value())`
/// is returned.
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) &;
template <class F> TL_OPTIONAL_11_CONSTEXPR auto and_then(F &&f) & {
using result = detail::invoke_result_t<F, T &>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: result(nullopt);
}
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) &&;
template <class F> TL_OPTIONAL_11_CONSTEXPR auto and_then(F &&f) && {
using result = detail::invoke_result_t<F, T &>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: result(nullopt);
}
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) const &;
template <class F> constexpr auto and_then(F &&f) const & {
using result = detail::invoke_result_t<F, const T &>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: result(nullopt);
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) const &&;
template <class F> constexpr auto and_then(F &&f) const && {
using result = detail::invoke_result_t<F, const T &>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: result(nullopt);
}
#endif
#else
/// \group and_then
/// Carries out some operation which returns an optional on the stored
/// object if there is one. \requires `std::invoke(std::forward<F>(f),
/// value())` returns a `std::optional<U>` for some `U`. \returns Let `U` be
/// the result of `std::invoke(std::forward<F>(f), value())`. Returns a
/// `std::optional<U>`. The return value is empty if `*this` is empty,
/// otherwise the return value of `std::invoke(std::forward<F>(f), value())`
/// is returned.
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) &;
template <class F>
TL_OPTIONAL_11_CONSTEXPR detail::invoke_result_t<F, T &> and_then(F &&f) & {
using result = detail::invoke_result_t<F, T &>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: result(nullopt);
}
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) &&;
template <class F>
TL_OPTIONAL_11_CONSTEXPR detail::invoke_result_t<F, T &> and_then(F &&f) && {
using result = detail::invoke_result_t<F, T &>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: result(nullopt);
}
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) const &;
template <class F>
constexpr detail::invoke_result_t<F, const T &> and_then(F &&f) const & {
using result = detail::invoke_result_t<F, const T &>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: result(nullopt);
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group and_then
/// \synopsis template <class F>\nconstexpr auto and_then(F &&f) const &&;
template <class F>
constexpr detail::invoke_result_t<F, const T &> and_then(F &&f) const && {
using result = detail::invoke_result_t<F, const T &>;
static_assert(detail::is_optional<result>::value,
"F must return an optional");
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: result(nullopt);
}
#endif
#endif
#if defined(TL_OPTIONAL_CXX14) && !defined(TL_OPTIONAL_GCC49) && \
!defined(TL_OPTIONAL_GCC54) && !defined(TL_OPTIONAL_GCC55)
/// \brief Carries out some operation on the stored object if there is one.
/// \returns Let `U` be the result of `std::invoke(std::forward<F>(f),
/// value())`. Returns a `std::optional<U>`. The return value is empty if
/// `*this` is empty, otherwise an `optional<U>` is constructed from the
/// return value of `std::invoke(std::forward<F>(f), value())` and is
/// returned.
///
/// \group map
/// \synopsis template <class F> constexpr auto map(F &&f) &;
template <class F> TL_OPTIONAL_11_CONSTEXPR auto map(F &&f) & {
return detail::optional_map_impl(*this, std::forward<F>(f));
}
/// \group map
/// \synopsis template <class F> constexpr auto map(F &&f) &&;
template <class F> TL_OPTIONAL_11_CONSTEXPR auto map(F &&f) && {
return detail::optional_map_impl(std::move(*this), std::forward<F>(f));
}
/// \group map
/// \synopsis template <class F> constexpr auto map(F &&f) const&;
template <class F> constexpr auto map(F &&f) const & {
return detail::optional_map_impl(*this, std::forward<F>(f));
}
/// \group map
/// \synopsis template <class F> constexpr auto map(F &&f) const&&;
template <class F> constexpr auto map(F &&f) const && {
return detail::optional_map_impl(std::move(*this), std::forward<F>(f));
}
#else
/// \brief Carries out some operation on the stored object if there is one.
/// \returns Let `U` be the result of `std::invoke(std::forward<F>(f),
/// value())`. Returns a `std::optional<U>`. The return value is empty if
/// `*this` is empty, otherwise an `optional<U>` is constructed from the
/// return value of `std::invoke(std::forward<F>(f), value())` and is
/// returned.
///
/// \group map
/// \synopsis template <class F> auto map(F &&f) &;
template <class F>
TL_OPTIONAL_11_CONSTEXPR decltype(detail::optional_map_impl(std::declval<optional &>(),
std::declval<F &&>()))
map(F &&f) & {
return detail::optional_map_impl(*this, std::forward<F>(f));
}
/// \group map
/// \synopsis template <class F> auto map(F &&f) &&;
template <class F>
TL_OPTIONAL_11_CONSTEXPR decltype(detail::optional_map_impl(std::declval<optional &&>(),
std::declval<F &&>()))
map(F &&f) && {
return detail::optional_map_impl(std::move(*this), std::forward<F>(f));
}
/// \group map
/// \synopsis template <class F> auto map(F &&f) const&;
template <class F>
constexpr decltype(detail::optional_map_impl(std::declval<const optional &>(),
std::declval<F &&>()))
map(F &&f) const & {
return detail::optional_map_impl(*this, std::forward<F>(f));
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group map
/// \synopsis template <class F> auto map(F &&f) const&&;
template <class F>
constexpr decltype(detail::optional_map_impl(std::declval<const optional &&>(),
std::declval<F &&>()))
map(F &&f) const && {
return detail::optional_map_impl(std::move(*this), std::forward<F>(f));
}
#endif
#endif
/// \brief Calls `f` if the optional is empty
/// \requires `std::invoke_result_t<F>` must be void or convertible to
/// `optional<T>`. \effects If `*this` has a value, returns `*this`.
/// Otherwise, if `f` returns `void`, calls `std::forward<F>(f)` and returns
/// `std::nullopt`. Otherwise, returns `std::forward<F>(f)()`.
///
/// \group or_else
/// \synopsis template <class F> optional<T> or_else (F &&f) &;
template <class F, detail::enable_if_ret_void<F> * = nullptr>
optional<T> TL_OPTIONAL_11_CONSTEXPR or_else(F &&f) & {
if (has_value())
return *this;
std::forward<F>(f)();
return nullopt;
}
/// \exclude
template <class F, detail::disable_if_ret_void<F> * = nullptr>
optional<T> TL_OPTIONAL_11_CONSTEXPR or_else(F &&f) & {
return has_value() ? *this : std::forward<F>(f)();
}
/// \group or_else
/// \synopsis template <class F> optional<T> or_else (F &&f) &&;
template <class F, detail::enable_if_ret_void<F> * = nullptr>
optional<T> or_else(F &&f) && {
if (has_value())
return std::move(*this);
std::forward<F>(f)();
return nullopt;
}
/// \exclude
template <class F, detail::disable_if_ret_void<F> * = nullptr>
optional<T> TL_OPTIONAL_11_CONSTEXPR or_else(F &&f) && {
return has_value() ? std::move(*this) : std::forward<F>(f)();
}
/// \group or_else
/// \synopsis template <class F> optional<T> or_else (F &&f) const &;
template <class F, detail::enable_if_ret_void<F> * = nullptr>
optional<T> or_else(F &&f) const & {
if (has_value())
return *this;
std::forward<F>(f)();
return nullopt;
}
/// \exclude
template <class F, detail::disable_if_ret_void<F> * = nullptr>
optional<T> TL_OPTIONAL_11_CONSTEXPR or_else(F &&f) const & {
return has_value() ? *this : std::forward<F>(f)();
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \exclude
template <class F, detail::enable_if_ret_void<F> * = nullptr>
optional<T> or_else(F &&f) const && {
if (has_value())
return std::move(*this);
std::forward<F>(f)();
return nullopt;
}
/// \exclude
template <class F, detail::disable_if_ret_void<F> * = nullptr>
optional<T> or_else(F &&f) const && {
return has_value() ? std::move(*this) : std::forward<F>(f)();
}
#endif
/// \brief Maps the stored value with `f` if there is one, otherwise returns
/// `u`.
///
/// \details If there is a value stored, then `f` is called with `**this`
/// and the value is returned. Otherwise `u` is returned.
///
/// \group map_or
template <class F, class U> U map_or(F &&f, U &&u) & {
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: std::forward<U>(u);
}
/// \group map_or
template <class F, class U> U map_or(F &&f, U &&u) && {
return has_value() ? detail::invoke(std::forward<F>(f), std::move(**this))
: std::forward<U>(u);
}
/// \group map_or
template <class F, class U> U map_or(F &&f, U &&u) const & {
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: std::forward<U>(u);
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group map_or
template <class F, class U> U map_or(F &&f, U &&u) const && {
return has_value() ? detail::invoke(std::forward<F>(f), std::move(**this))
: std::forward<U>(u);
}
#endif
/// \brief Maps the stored value with `f` if there is one, otherwise calls
/// `u` and returns the result.
///
/// \details If there is a value stored, then `f` is
/// called with `**this` and the value is returned. Otherwise
/// `std::forward<U>(u)()` is returned.
///
/// \group map_or_else
/// \synopsis template <class F, class U>\nauto map_or_else(F &&f, U &&u) &;
template <class F, class U>
detail::invoke_result_t<U> map_or_else(F &&f, U &&u) & {
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: std::forward<U>(u)();
}
/// \group map_or_else
/// \synopsis template <class F, class U>\nauto map_or_else(F &&f, U &&u)
/// &&;
template <class F, class U>
detail::invoke_result_t<U> map_or_else(F &&f, U &&u) && {
return has_value() ? detail::invoke(std::forward<F>(f), std::move(**this))
: std::forward<U>(u)();
}
/// \group map_or_else
/// \synopsis template <class F, class U>\nauto map_or_else(F &&f, U &&u)
/// const &;
template <class F, class U>
detail::invoke_result_t<U> map_or_else(F &&f, U &&u) const & {
return has_value() ? detail::invoke(std::forward<F>(f), **this)
: std::forward<U>(u)();
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group map_or_else
/// \synopsis template <class F, class U>\nauto map_or_else(F &&f, U &&u)
/// const &&;
template <class F, class U>
detail::invoke_result_t<U> map_or_else(F &&f, U &&u) const && {
return has_value() ? detail::invoke(std::forward<F>(f), std::move(**this))
: std::forward<U>(u)();
}
#endif
/// \returns `u` if `*this` has a value, otherwise an empty optional.
template <class U>
constexpr optional<typename std::decay<U>::type> conjunction(U &&u) const {
using result = optional<detail::decay_t<U>>;
return has_value() ? result{u} : result{nullopt};
}
/// \returns `rhs` if `*this` is empty, otherwise the current value.
/// \group disjunction
TL_OPTIONAL_11_CONSTEXPR optional disjunction(const optional &rhs) & {
return has_value() ? *this : rhs;
}
/// \group disjunction
constexpr optional disjunction(const optional &rhs) const & {
return has_value() ? *this : rhs;
}
/// \group disjunction
TL_OPTIONAL_11_CONSTEXPR optional disjunction(const optional &rhs) && {
return has_value() ? std::move(*this) : rhs;
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group disjunction
constexpr optional disjunction(const optional &rhs) const && {
return has_value() ? std::move(*this) : rhs;
}
#endif
/// \group disjunction
TL_OPTIONAL_11_CONSTEXPR optional disjunction(optional &&rhs) & {
return has_value() ? *this : std::move(rhs);
}
/// \group disjunction
constexpr optional disjunction(optional &&rhs) const & {
return has_value() ? *this : std::move(rhs);
}
/// \group disjunction
TL_OPTIONAL_11_CONSTEXPR optional disjunction(optional &&rhs) && {
return has_value() ? std::move(*this) : std::move(rhs);
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group disjunction
constexpr optional disjunction(optional &&rhs) const && {
return has_value() ? std::move(*this) : std::move(rhs);
}
#endif
/// Takes the value out of the optional, leaving it empty
/// \group take
optional take() & {
optional ret = *this;
reset();
return ret;
}
/// \group take
optional take() const & {
optional ret = *this;
reset();
return ret;
}
/// \group take
optional take() && {
optional ret = std::move(*this);
reset();
return ret;
}
#ifndef TL_OPTIONAL_NO_CONSTRR
/// \group take
optional take() const && {
optional ret = std::move(*this);
reset();
return ret;
}
#endif
using value_type = T &;
/// Constructs an optional that does not contain a value.
/// \group ctor_empty
constexpr optional() noexcept : m_value(nullptr) {}
/// \group ctor_empty
constexpr optional(nullopt_t) noexcept : m_value(nullptr) {}
/// Copy constructor
///
/// If `rhs` contains a value, the stored value is direct-initialized with
/// it. Otherwise, the constructed optional is empty.
TL_OPTIONAL_11_CONSTEXPR optional(const optional &rhs) noexcept = default;
/// Move constructor
///
/// If `rhs` contains a value, the stored value is direct-initialized with
/// it. Otherwise, the constructed optional is empty.
TL_OPTIONAL_11_CONSTEXPR optional(optional &&rhs) = default;
/// Constructs the stored value with `u`.
/// \synopsis template <class U=T> constexpr optional(U &&u);
template <class U = T,
detail::enable_if_t<!detail::is_optional<detail::decay_t<U>>::value>
* = nullptr>
constexpr optional(U &&u) : m_value(std::addressof(u)) {
static_assert(std::is_lvalue_reference<U>::value, "U must be an lvalue");
}
/// \exclude
template <class U>
constexpr explicit optional(const optional<U> &rhs) : optional(*rhs) {}
/// No-op
~optional() = default;
/// Assignment to empty.
///
/// Destroys the current value if there is one.
optional &operator=(nullopt_t) noexcept {
m_value = nullptr;
return *this;
}
/// Copy assignment.
///
/// Rebinds this optional to the referee of `rhs` if there is one. Otherwise
/// resets the stored value in `*this`.
optional &operator=(const optional &rhs) = default;
/// Rebinds this optional to `u`.
///
/// \requires `U` must be an lvalue reference.
/// \synopsis optional &operator=(U &&u);
template <class U = T,
detail::enable_if_t<!detail::is_optional<detail::decay_t<U>>::value>
* = nullptr>
optional &operator=(U &&u) {
static_assert(std::is_lvalue_reference<U>::value, "U must be an lvalue");
m_value = std::addressof(u);
return *this;
}
/// Converting copy assignment operator.
///
/// Rebinds this optional to the referee of `rhs` if there is one. Otherwise
/// resets the stored value in `*this`.
template <class U> optional &operator=(const optional<U> &rhs) {
m_value = std::addressof(rhs.value());
return *this;
}
/// Constructs the value in-place, destroying the current one if there is
/// one.
///
/// \group emplace
template <class... Args> T &emplace(Args &&... args) noexcept {
static_assert(std::is_constructible<T, Args &&...>::value,
"T must be constructible with Args");
*this = nullopt;
this->construct(std::forward<Args>(args)...);
}
/// Swaps this optional with the other.
///
/// If neither optionals have a value, nothing happens.
/// If both have a value, the values are swapped.
/// If one has a value, it is moved to the other and the movee is left
/// valueless.
void swap(optional &rhs) noexcept { std::swap(m_value, rhs.m_value); }
/// \returns a pointer to the stored value
/// \requires a value is stored
/// \group pointer
/// \synopsis constexpr const T *operator->() const;
constexpr const T *operator->() const { return m_value; }
/// \group pointer
/// \synopsis constexpr T *operator->();
TL_OPTIONAL_11_CONSTEXPR T *operator->() { return m_value; }
/// \returns the stored value
/// \requires a value is stored
/// \group deref
/// \synopsis constexpr T &operator*();
TL_OPTIONAL_11_CONSTEXPR T &operator*() { return *m_value; }
/// \group deref
/// \synopsis constexpr const T &operator*() const;
constexpr const T &operator*() const { return *m_value; }
/// \returns whether or not the optional has a value
/// \group has_value
constexpr bool has_value() const noexcept { return m_value != nullptr; }
/// \group has_value
constexpr explicit operator bool() const noexcept {
return m_value != nullptr;
}
/// \returns the contained value if there is one, otherwise throws
/// [bad_optional_access]
/// \group value
/// synopsis constexpr T &value();
TL_OPTIONAL_11_CONSTEXPR T &value() {
if (has_value())
return *m_value;
throw bad_optional_access();
}
/// \group value
/// \synopsis constexpr const T &value() const;
TL_OPTIONAL_11_CONSTEXPR const T &value() const {
if (has_value())
return *m_value;
throw bad_optional_access();
}
/// \returns the stored value if there is one, otherwise returns `u`
/// \group value_or
template <class U> constexpr T value_or(U &&u) const & {
static_assert(std::is_copy_constructible<T>::value &&
std::is_convertible<U &&, T>::value,
"T must be copy constructible and convertible from U");
return has_value() ? **this : static_cast<T>(std::forward<U>(u));
}
/// \group value_or
template <class U> TL_OPTIONAL_11_CONSTEXPR T value_or(U &&u) && {
static_assert(std::is_move_constructible<T>::value &&
std::is_convertible<U &&, T>::value,
"T must be move constructible and convertible from U");
return has_value() ? **this : static_cast<T>(std::forward<U>(u));
}
/// Destroys the stored value if one exists, making the optional empty
void reset() noexcept { m_value = nullptr; }
private:
T *m_value;
}; // namespace tl
} // namespace tl
namespace std {
// TODO SFINAE
template <class T> struct hash<tl::optional<T>> {
::std::size_t operator()(const tl::optional<T> &o) const {
if (!o.has_value())
return 0;
return std::hash<tl::detail::remove_const_t<T>>()(*o);
}
};
} // namespace std
#endif
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