[#beman-optional-optional-03]
= xref:beman.adoc[beman]::xref:beman/optional.adoc[optional]::optional
:relfileprefix: ../../
:mrdocs:

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class T>
class optional;
----

== Types

[cols=2]
|===
| Name
| Description
| xref:beman/optional/optional-03/const_iterator.adoc[`const_iterator`] 
| Type alias for the const iterator type of the optional.
| xref:beman/optional/optional-03/iterator.adoc[`iterator`] 
| Type alias for the iterator type of the optional.
| xref:beman/optional/optional-03/value_type.adoc[`value_type`] 
| Type alias for the value type stored in the optional.
|===

== Member Functions

[cols=2]
|===
| Name
| Description
| xref:beman/optional/optional-03/2constructor-026.adoc[`optional`]         [.small]#[constructor]#
| Constructors
| xref:beman/optional/optional-03/2destructor-01.adoc[`~optional`] [.small]#[destructor]#
| Destructors
| xref:beman/optional/optional-03/operator_assign-01.adoc[`operator=`] 
| Assignment operators
| xref:beman/optional/optional-03/and_then-02.adoc[`and_then`] 
| Returns an optional containing the result of applying `f` to the stored value.
| xref:beman/optional/optional-03/begin-09.adoc[`begin`] 
| `begin` overloads
| xref:beman/optional/optional-03/emplace-07.adoc[`emplace`] 
| `emplace` overloads
| xref:beman/optional/optional-03/end-01.adoc[`end`] 
| `end` overloads
| xref:beman/optional/optional-03/has_value.adoc[`has_value`] 
| Returns whether or not the optional has a value.
| xref:beman/optional/optional-03/operator_star-03.adoc[`operator*`] 
| Returns a reference to the stored value.
| xref:beman/optional/optional-03/operator_ptr-094.adoc[`operator‐>`] 
| Returns a pointer to the stored value.
| xref:beman/optional/optional-03/or_else-01.adoc[`or_else`] 
| Returns an optional containing the stored value if it has one, or the result of applying `f` to the optional if it does not.
| xref:beman/optional/optional-03/reset.adoc[`reset`] 
| Resets the optional to an empty state, destroying the stored value if there is one.
| xref:beman/optional/optional-03/swap.adoc[`swap`] 
| Swaps this optional with the other.
| xref:beman/optional/optional-03/transform-08.adoc[`transform`] 
| Returns an optional containing the result of applying `f` to the stored value, or a default value if there is no stored value.
| xref:beman/optional/optional-03/value-028.adoc[`value`] 
| Returns a reference to the stored value.
| xref:beman/optional/optional-03/value_or-03.adoc[`value_or`] 
| Returns a reference to the stored value.
| xref:beman/optional/optional-03/2conversion.adoc[`operator bool`] 
| Converts the optional to a boolean indicating whether it has a value.
|===

== Data Members

[cols=2]
|===
| Name
| Description
| xref:beman/optional/optional-03/_.adoc[`_`] [.small]#[variant member]#
| The empty state of the optional.
| xref:beman/optional/optional-03/value_.adoc[`value_`] [.small]#[variant member]#
| The stored value of the optional.
|===

== Friends

[cols=2]
|===
| Name
| Description
| `beman::optional::optional`
| 
|===

== Non-Member Functions

[cols=2]
|===
| Name
| Description
| xref:beman/optional/operator_not_eq-0d8.adoc[`operator!=`]
| Inequality operator
| xref:beman/optional/operator_not_eq-0e.adoc[`operator!=`]
| Inequality operator
| xref:beman/optional/operator_lt-08.adoc[`operator<`]
| Less‐than operator
| xref:beman/optional/operator_lt-0d.adoc[`operator<`]
| Less‐than operator
| xref:beman/optional/operator_le-01.adoc[`operator<=`]
| Less‐than‐or‐equal operator
| xref:beman/optional/operator_le-0f.adoc[`operator<=`]
| Less‐than‐or‐equal operator
| xref:beman/optional/operator_3way-02.adoc[`operator<=>`]
| Three‐way comparison operator
| xref:beman/optional/operator_3way-09.adoc[`operator<=>`]
| Three‐way comparison operator
| xref:beman/optional/operator_3way-0a.adoc[`operator<=>`]
| Three‐way comparison operator
| xref:beman/optional/operator_eq-00.adoc[`operator==`]
| Equality operator
| xref:beman/optional/operator_eq-08.adoc[`operator==`]
| Equality operator
| xref:beman/optional/operator_eq-09.adoc[`operator==`]
| Equality operator
| xref:beman/optional/operator_gt-08.adoc[`operator>`]
| Greater‐than operator
| xref:beman/optional/operator_gt-0d.adoc[`operator>`]
| Greater‐than operator
| xref:beman/optional/operator_ge-00.adoc[`operator>=`]
| Greater‐than‐or‐equal operator
| xref:beman/optional/operator_ge-0f.adoc[`operator>=`]
| Greater‐than‐or‐equal operator
|===


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