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

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< cpp‎ | utility‎ | expected
 
 
Utilities library
General utilities
Relational operators (deprecated in C++20)
 
 
template< class G = E >
constexpr E error_or( G&& default_value ) const&;
(1) (since C++23)
template< class G = E >
constexpr E error_or( G&& default_value ) &&;
(2) (since C++23)

Returns the unexpected value if it exists, otherwise returns default_value.

1) If std::is_copy_constructible_v<E> or std::is_convertible_v<G, E> is false, the program is ill-formed.
2) If std::is_move_constructible_v<E> or std::is_convertible_v<G, E> is false, the program is ill-formed.

Parameters

default_value - the value to use in case *this does not contain an unexpected value
Type requirements

Return value

1) has_value() ? std::forward<G>(default_value) : error()
2) has_value() ? std::forward<G>(default_value) : std::move(error())

Example

See also

returns the unexpected value
(public member function)