[#beman-optional-is_derived_from_optional]
= xref:beman.adoc[beman]::xref:beman/optional.adoc[optional]::is&lowbar;derived&lowbar;from&lowbar;optional
:relfileprefix: ../../
:mrdocs:

== Synopsis

Declared in `&lt;beman&sol;optional&sol;optional&period;hpp&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template&lt;class T&gt;
concept is&lowbar;derived&lowbar;from&lowbar;optional = requires(const T&amp; t) &lcub; &sol;&sol; exposition only
    &lsqb;&rsqb;&lt;class U&gt;(const optional&lt;U&gt;&amp;) &lcub;&rcub;(t)&semi;
&rcub;;
----


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