[#absl-exchange]
= xref:absl.adoc[absl]::exchange
:relfileprefix: ../
:mrdocs:

Replace the value of an object and return its old value.

== Synopsis

Declared in `<absl/utility/utility.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class T1,
    class T2 = T1>
[[deprecated]]
constexpr
T1
exchange(
    T1& obj,
    T2&& new_value) noexcept(/* see-below */);
----

[WARNING]
====
https://en.cppreference.com/cpp/language/attributes/deprecated[Deprecated^]. Use of this entity is allowed but discouraged.
====
== Exception specification

This function is potentially-throwing unless `noexcept(std::exchange(std::declval<T1 &>(), std::declval<T2>()))`.

== Return Value

The previous value of `obj`.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *obj*
| The object whose value is replaced.
| *new_value*
| The value to assign to `obj`.
|===


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