std::experimental::optional::value_or

 

C++

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Experimental libraries

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optional (library fundamentals TS)

any (library fundamentals TS)

basic_string_view (library fundamentals TS)

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std::experimental::optional

Member functions

optional::optional

optional::~optional

optional::operator=

Observers

optional::operator->optional::operator*

optional::operator bool

optional::value

optional::value_or

Modifiers

optional::emplace

optional::swap

Non-member functions

operator==operator<

make_optional

swap

Helper classes

hash

 

template< class U > constexpr T value_or( U&& value ) const&;		(library fundamentals TS)
template< class U > T value_or( U&& value ) &&;		(library fundamentals TS)

Returns the contained value if *this is in engaged state, otherwise returns value.

Parameters

value	-	the value to exchange
Type requirements
- T must meet the requirements of CopyConstructible in order to use overload (1).
- T must meet the requirements of MoveConstructible in order to use overload (2).
- U&& must be convertible to T

Return value

The current value if *this is in engaged state, or value otherwise.

Exceptions

Any exception thrown by the selected constructor of T.

If an exception is thrown, the exception safety guarantee is as follows:

• If *this was in engaged state, the contents of the contained value depend on the exception safety guarantee of T's constructor.
• Otherwise, the state of *this does not change. The contents of value depend on the exception safety guarantee of T's constructor.

See also

value

returns the contained value (public member function)