[#bsl-variant]
= xref:bsl.adoc[bsl]::variant
:relfileprefix: ../
:mrdocs:

Type‐safe discriminated union of alternative types.

== Synopsis

Declared in `<bslstl_variant.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class t_HEAD,
    class... t_TAIL>
class variant;
----

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:bsl/variant/allocator_type.adoc[`allocator_type`] 
| Type alias to the allocator type used by `variant`.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/variant/2constructor-0e.adoc[`variant`]         [.small]#[constructor]#
| Constructors
| xref:bsl/variant/operator_assign-07.adoc[`operator=`] 
| Assignment operators
| xref:bsl/variant/emplace-03.adoc[`emplace`] 
| `emplace` overloads
| xref:bsl/variant/get_allocator.adoc[`get_allocator`] 
| Return a copy of this object's allocator.
| xref:bsl/variant/index.adoc[`index`] 
| Return the index of the currently managed alternative.
| xref:bsl/variant/swap.adoc[`swap`] 
| Efficiently exchange the value of this object with `other`'s value.
| xref:bsl/variant/valueless_by_exception.adoc[`valueless_by_exception`] 
| Return `true` if this object is valueless by exception.
| xref:bsl/variant/2conversion-0e.adoc[`operator BloombergLP::bslmf::NestedTraitDeclaration<variant, IsBitwiseMoveable, (BloombergLP::bslstl::Variant_IsBitwiseMoveableAll<t_HEAD, t_TAIL...>::value)>`] 
| Nested trait declaration for `IsBitwiseMoveable`.
| xref:bsl/variant/2conversion-02.adoc[`operator BloombergLP::bslmf::NestedTraitDeclaration<variant, UsesAllocatorArgT, (BloombergLP::bslstl::Variant_UsesBslmaAllocatorAny<t_HEAD, t_TAIL...>::value)>`] 
| Nested trait declaration for `UsesAllocatorArgT`.
| xref:bsl/variant/2conversion-0b.adoc[`operator BloombergLP::bslmf::NestedTraitDeclaration<variant, UsesBslmaAllocator, (BloombergLP::bslstl::Variant_UsesBslmaAllocatorAny<t_HEAD, t_TAIL...>::value)>`] 
| Nested trait declaration for `UsesBslmaAllocator`.
|===


== Friends

[cols="1,4"]
|===
| Name| Description
| `xref:BloombergLP/bslstl/Variant_Base.adoc[BloombergLP::bslstl::Variant_Base]`
| Define the data representation and special member functions of `bsl::variant`.
|===

== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/get-002.adoc[`get`]
| See the first `get` overload above.
| xref:bsl/get-035.adoc[`get`]
| See the first `get` overload above.
| xref:bsl/get-06.adoc[`get`]
| See the first `get` overload above.
| xref:bsl/get-0b5.adoc[`get`]
| Return a reference to the alternative at index `t_INDEX` in `obj`.
| xref:bsl/get-0e3.adoc[`get`]
| See the first `get` overload above.
| xref:bsl/get-0e6.adoc[`get`]
| See the first `get` overload above.
| xref:bsl/get-0ea.adoc[`get`]
| Return a reference to the alternative of type `t_TYPE` in `obj`.
| xref:bsl/get-0ee.adoc[`get`]
| See the first `get` overload above.
| xref:bsl/get_if-06.adoc[`get_if`]
| Return a pointer to the `t_TYPE` alternative in `obj` if active.
| xref:bsl/get_if-09.adoc[`get_if`]
| Return a pointer to the `t_TYPE` alternative in `obj` if active.
| xref:bsl/get_if-0a.adoc[`get_if`]
| Return a pointer to the alternative at index `t_INDEX`, or null.
| xref:bsl/get_if-0d.adoc[`get_if`]
| Return a pointer to the alternative at index `t_INDEX` in `obj`, or null.
| xref:bsl/holds_alternative.adoc[`holds_alternative`]
| Return `true` if `obj` currently holds the `t_TYPE` alternative.
| xref:bsl/operator_not_eq-023.adoc[`operator!=`]
| Return `true` if `lhs` and `rhs` are not equal.
| xref:bsl/operator_lt-01d.adoc[`operator<`]
| Return `true` if `lhs` is less than `rhs`.
| xref:bsl/operator_le-00.adoc[`operator<=`]
| Return `true` if `lhs` is less than or equal to `rhs`.
| xref:bsl/operator_3way-09.adoc[`operator<=>`]
| Return the three‐way comparison result of `lhs` and `rhs`.
| xref:bsl/operator_eq-058.adoc[`operator==`]
| Return `true` if `lhs` and `rhs` are equal.
| xref:bsl/operator_gt-014.adoc[`operator>`]
| Return `true` if `lhs` is greater than `rhs`.
| xref:bsl/operator_ge-07a.adoc[`operator>=`]
| Return `true` if `lhs` is greater than or equal to `rhs`.
| xref:bsl/swap-0f5.adoc[`swap`]
| Efficiently exchange the values of the specified `lhs` and `rhs` objects.
|===


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