[#mrdocs-operator_3way-081]
= xref:mrdocs.adoc[mrdocs]::operator<=>
:relfileprefix: ../
:mrdocs:

Performs a three‐way comparison between two Optional values. If both are engaged, compares their contained values; otherwise, compares engagement state.

== Synopsis

Declared in `<mrdocs/ADT/Optional.hpp>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    typename T,
    std::three_way_comparable_with<T> U>
[[nodiscard]]
constexpr
std::compare_three_way_result_t<T, U>
operator<=>(
    xref:mrdocs/Optional-03.adoc[Optional<T>] const& x,
    xref:mrdocs/Optional-03.adoc[Optional<U>] const& y);
----

== Return Value

The result of the three‐way comparison between the optionals or their values.

[NOTE]
====
The return value https://en.cppreference.com/cpp/language/attributes/nodiscard[should not be discarded^].
====
== Parameters

[cols="1,4"]
|===
| Name| Description
| *x*
| The left operand
| *y*
| The right operand
|===


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