[#beman-optional-operator_eq-04]
= xref:beman.adoc[beman]::xref:beman/optional.adoc[optional]::operator==
:relfileprefix: ../../
:mrdocs:

Equality operators

== Synopses

Declared in `<beman/optional/optional.hpp>`

Compares two `nullopt_t` objects for equality.


[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
constexpr
bool
xref:beman/optional/operator_eq-03.adoc[operator==](
    xref:beman/optional/nullopt_t.adoc[nullopt_t] lhs,
    xref:beman/optional/nullopt_t.adoc[nullopt_t] rhs) noexcept;
----

[.small]#xref:beman/optional/operator_eq-03.adoc[_» more..._]#

Compares two optionals for equality.


[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    typename T,
    typename U>
constexpr
bool
xref:beman/optional/operator_eq-08.adoc[operator==](
    xref:beman/optional/optional-03.adoc[optional<T>] const& lhs,
    xref:beman/optional/optional-03.adoc[optional<U>] const& rhs)
requires detail::optional_eq_rel<T, U>;
----

[.small]#xref:beman/optional/operator_eq-08.adoc[_» more..._]#

Compares an optional against `nullopt`.


[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class T>
constexpr
bool
xref:beman/optional/operator_eq-00.adoc[operator==](
    xref:beman/optional/optional-03.adoc[optional<T>] const& lhs,
    xref:beman/optional/nullopt_t.adoc[nullopt_t] rhs) noexcept;
----

[.small]#xref:beman/optional/operator_eq-00.adoc[_» more..._]#

Compares an engaged optional's value against a value for equality.


[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    typename T,
    typename U>
constexpr
bool
xref:beman/optional/operator_eq-09.adoc[operator==](
    xref:beman/optional/optional-03.adoc[optional<T>] const& lhs,
    U const& rhs)
requires (!detail::is_optional<U>) && detail::optional_eq_rel<T, U>;
----

[.small]#xref:beman/optional/operator_eq-09.adoc[_» more..._]#

Compares a value against an engaged optional's value for equality.


[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    typename T,
    typename U>
constexpr
bool
xref:beman/optional/operator_eq-0b.adoc[operator==](
    T const& lhs,
    xref:beman/optional/optional-03.adoc[optional<U>] const& rhs)
requires (!detail::is_optional<T>) && detail::optional_eq_rel<T, U>;
----

[.small]#xref:beman/optional/operator_eq-0b.adoc[_» more..._]#

== Return Value

* Always `true`, since all `nullopt_t` objects compare equal.
* `true` if both are disengaged, or both are engaged and their contained values are equal.
* `true` if `lhs` is disengaged.
* `true` if `lhs` is engaged and its contained value equals `rhs.`
* `true` if `rhs` is engaged and `lhs` equals its contained value.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *lhs*
| The left‐hand `nullopt_t` object.
| *rhs*
| The right‐hand `nullopt_t` object.
|===


[.small]#Created with https://www.mrdocs.com[MrDocs]#