[#BloombergLP-bslstl-Variant_FunctionId]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslstl.adoc[bslstl]::Variant_FunctionId
:relfileprefix: ../../
:mrdocs:

Component‐private vtable entry invoking a tagged visitor on alternative `t_INDEX`.

== Synopsis

Declared in `<bslstl_variant.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class t_RET,
    class t_VISITOR,
    class t_VARIANT,
    size_t t_INDEX>
struct Variant_FunctionId;
----

== Static Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslstl/Variant_FunctionId/functionImpl.adoc[`functionImpl`] 
| This component‐private function invokes the specified `visitor` with a `bsl::in_place_index_t` tag representing the value of (template parameter) `t_INDEX` and the active alternative object of the specified `variant`, implicitly converting the return type to (template parameter) `t_RET`. The behavior is undefined unless `t_INDEX` is the index of the active alternative.
|===



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