[#bsl-optional-072-2constructor-0ae]
= xref:bsl.adoc[bsl]::xref:bsl/optional-072.adoc[optional]::optional
:relfileprefix: ../../
:mrdocs:

Create a disengaged `optional` object&period; Use the currently installed default allocator to supply memory&period; This constructor can be called in constant expressions only when `t&lowbar;TYPE` is not allocator&hyphen;aware&period;

== Synopsis

Declared in `&lt;bslstl&lowbar;optional&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
constexpr
optional() noexcept;
----


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