TartanLlama/optional
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This commit is contained in:
Simon Brand
2017-09-29 20:14:29 +01:00
parent 4287be6e74
commit 4fc7d9cf61
1 changed files with 30 additions and 9 deletions
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39
optional.hpp
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@@ -204,19 +204,23 @@ namespace std {
namespace tl { namespace tl {
namespace detail {
template <class T>
struct optional_base : <T> {
};
}
template <class T> template <class T>
class optional { class optional : private detail::optional_base<T> {
public: public:
using value_type = T; using value_type = T;
// [optional.ctor], constructors // [optional.ctor], constructors
constexpr optional() noexcept : m_has_value(false) { constexpr optional() noexcept = default;
new (&m_storage.d) dummy; constexpr optional(nullopt_t) noexcept = default;
} constexpr optional(const optional& rhs) = default;
constexpr optional(nullopt_t) noexcept : optional() {} constexpr optional(optional&&);
constexpr optional(const optional& rhs);
constexpr optional(optional&&) noexcept(see below);
template <class... Args> template <class... Args>
constexpr explicit optional(in_place_t, Args&&...); constexpr explicit optional(in_place_t, Args&&...);
template <class U, class... Args> template <class U, class... Args>
@@ -242,7 +246,24 @@ template <class T>
template <class U, class... Args> T& emplace(initializer_list<U>, Args&&...); template <class U, class... Args> T& emplace(initializer_list<U>, Args&&...);
// [optional.swap], swap // [optional.swap], swap
void swap(optional&) noexcept(see below); void swap(optional& rhs)
noexcept(std::is_nothrow_move_constructible_v<T>::value && std::is_nothrow_swappable<T>::value)
{
if (lhs.has_value()) {
if (rhs.has_value()) {
using std::swap;
swap(value(), rhs.value());
}
else {
new (&rhs.m_storage.t) T (std::move(m_storage.t));
m_storage.t.T::~T();
}
}
else if (rhs.has_value()) {
new (&m_storage.t) T (std::move(rhs.m_storage.t));
rhs.m_storage.t.T::~T();
}
}
// [optional.observe], observers // [optional.observe], observers
constexpr const T* operator->() const { constexpr const T* operator->() const {