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std::experimental::optional::optional

From cppreference.com
constexpr optional();
(1) (library fundamentals TS)
constexpr optional( std::nullopt_t );
(1) (library fundamentals TS)
optional( const optional& other);
(2) (library fundamentals TS)
optional( optional&& other );
(3) (library fundamentals TS)
constexpr optional( const T& value );
(4) (library fundamentals TS)
constexpr optional( T&& value );
(5) (library fundamentals TS)
template< class... Args >
constexpr explicit optional( std::in_place_t, Args&&... args );
(6) (library fundamentals TS)
template< class U, class... Args >

constexpr explicit optional( std::in_place_t, std::initializer_list<U> ilist,

                             Args&&... args );
(7) (library fundamentals TS)

Constructs a new optional object.

1) Constructs the object without initializing the contained value. The object is in disengaged state after the call.
2-3) Initializes the contained value by copying (2) or moving(3) the contained value of other, but only if other is engaged. other is still in engaged state if it was in engaged state before the call.
4-7) Initializes the contained value from various sources. *this is in engaged state after the call.
4) Initializes the contained value by copying value.
5) Initializes the contained value by moving value.
6) Initializes the contained value by constructing it in-place and passing args... to the constructor.
7) Initializes the contained value by constructing it in-place and passing the initializer list ilist and arguments args... to the constructor. The function does not participate in the overload resolution if
std::is_constructible<T, std::initializer_list<U>&, Args&&...>::value != true

[edit] Parameters

other - another optional object whose contained value to copy
value - value to initialize the contained value with
args... - arguments to initialize the contained value with
ilist - initializer list to initialize the contained value with
Type requirements
-
T must meet the requirements of CopyConstructible in order to use overloads (2,4).
-
T must meet the requirements of MoveConstructible in order to use overloads (3,5).

[edit] Exceptions

1)
noexcept specification:  
noexcept
  
2) Throws any exception thrown by the constructor of T.
3) Throws any exception thrown by the constructor of T. Has the following noexcept declaration:
noexcept specification:  (since C++11)
.
4-5) Throws any exception thrown by the constructor of T.

[edit] See also

creates an optional object
(function template) [edit]