[#bsl-swap-03fc]
= xref:bsl.adoc[bsl]::swap
:relfileprefix: ../
:mrdocs:

Exchange the stop states referred to by `lhs` and `rhs`.

== Synopsis

Declared in `<bslstl_stoptoken.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
void
swap(
    xref:bsl/stop_source.adoc[stop_source]& lhs,
    xref:bsl/stop_source.adoc[stop_source]& rhs) noexcept;
----

[NOTE]
====
This function is a https://en.cppreference.com/w/cpp/language/friend[hidden friend] of xref:bsl/stop_source.adoc[stop_source], declared only inside that class: it can be found only through argument-dependent lookup.
====

== Description

Set `lhs` to refer to the stop state (or lack thereof) that `rhs` referred to before the call, and vice versa. Implementation note: this function is required by the standard to be a hidden friend ([hidden.friends], [stopsource.general]).

== Parameters

[cols="1,4"]
|===
| Name| Description
| *lhs*
| first source participating in the swap
| *rhs*
| second source participating in the swap
|===


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