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std::expected<T,E>::value_or

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< cpp‎ | utility‎ | expected
 
 
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template< class U >
constexpr T value_or( U&& default_value ) const&;
(1) (since C++23)
template< class U >
constexpr T value_or( U&& default_value ) &&;
(2) (since C++23)

Returns the contained value if *this contains an expected value, otherwise returns default_value.

1) Returns bool(*this) ? **this : static_cast<T>(std::forward<U>(default_value))
2) Returns bool(*this) ? std::move(**this) : static_cast<T>(std::forward<U>(default_value))

Contents

[edit] Parameters

default_value - the value to use in case *this does not contain an expected value
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

[edit] Return value

The currently contained value if *this contains an expected value, or default_value otherwise.

[edit] Exceptions

Any exception thrown by the selected constructor of the return value T.

[edit] Notes

If T is (possibly cv-qualified) void, this member is not declared.

[edit] Example

[edit] See also

(C++23)
returns the expected value
(public member function) [edit]