[#beman-optional-optional-06-2constructor-08]
= xref:beman.adoc[beman]::xref:beman/optional.adoc[optional]::xref:beman/optional/optional-06.adoc[optional<T&>]::optional
:relfileprefix: ../../../
:mrdocs:

Constructs an optional from another optional of type U.

== Synopsis

Declared in `<beman/optional/optional.hpp>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class U>
requires (std::is_constructible_v<T&, U> && !std::is_same_v<std::remove_cv_t<T>, optional<U>> &&
             !std::is_same_v<T&, U> && !detail::reference_constructs_from_temporary_v<T&, U>)
constexpr
explicit(!std::is_convertible_v<U, T &>)
optional(xref:beman/optional/optional-03.adoc[optional<U>]&& rhs) noexcept(noexcept(std::is_nothrow_constructible_v<T &, U>));
----

== Description

Constructs the stored value from the rhs if it has a value, otherwise constructs an empty optional. If `T&` can be constructed from a temporary, this constructor is deleted to prevent binding a temporary to a reference.


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