[#bsl-swap-04d]
= xref:bsl.adoc[bsl]::swap
:relfileprefix: ../
:mrdocs:

Exchange the values of two optionals.

== Synopsis

Declared in `<bslstl_optional.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class t_TYPE>
void
swap(
    xref:bsl/optional-072.adoc[bsl::optional<t_TYPE>]& lhs,
    xref:bsl/optional-072.adoc[bsl::optional<t_TYPE>]& rhs)
requires BloombergLP::bslma::UsesBslmaAllocator<t_TYPE>::value;
----

== Description

Efficiently exchange the values of the specified `lhs` and `rhs` objects. This method provides the no‐throw exception‐safety guarantee if the template parameter `t_TYPE` provides that guarantee, `lhs` and `rhs` have equal allocators, and `lhs.hasValue() == rhs.hasValue()`.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *lhs*
| left‐hand operand
| *rhs*
| right‐hand operand
|===


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