[#bsl-optional-072-2constructor-0d3]
= xref:bsl.adoc[bsl]::xref:bsl/optional-072.adoc[optional]::optional
:relfileprefix: ../../
:mrdocs:

Create a disengaged `optional` object. Use the currently installed default allocator to supply memory. This constructor can be called in constant expressions only when `t_TYPE` is not allocator‐aware.

== Synopsis

Declared in `<bslstl_optional.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
constexpr
optional(xref:bsl/nullopt_t.adoc[bsl::nullopt_t]) noexcept;
----


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