[#bsl-swap-00c]
= xref:bsl.adoc[bsl]::swap
:relfileprefix: ../
:mrdocs:

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 and the result of the `hasValue` method for `lhs` and `rhs` is the same. This function can be called in constant expressions only if `t_TYPE` is not allocator‐aware.

== 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,
    std::optional<t_TYPE>& rhs)
requires !BloombergLP::bslma::UsesBslmaAllocator<t_TYPE>::value;
----


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