[#absl-optional_ref-0c-2constructor-06]
= xref:absl.adoc[absl]::xref:absl/optional_ref-0c.adoc[optional&lowbar;ref]::optional&lowbar;ref
:relfileprefix: ../../
:mrdocs:

Constructs an `optional&lowbar;ref` from a const `std&colon;&colon;optional`&period;

== Synopsis

Declared in `&lt;absl&sol;types&sol;optional&lowbar;ref&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template&lt;
    typename U,
    typename = xref:absl/optional_ref-0c.adoc[EnableIfConvertibleFrom&lt;U const&gt;]&gt;
constexpr
optional&lowbar;ref(std::optional&lt;U&gt; const& input);
----

== Parameters

[cols="1,4"]
|===
| Name| Description
| *input*
| The optional whose value (if any) is referred to&period;
|===


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