[#bsl-Pair_First-00-2constructor-02]
= xref:bsl.adoc[bsl]::xref:bsl/Pair_First-00.adoc[Pair_First]::Pair_First
:relfileprefix: ../../
:mrdocs:

Construct the `first` member from the elements of `argsPack`.

== Synopsis

Declared in `<bslstl_pair.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class... ARGS,
    size_t I...>
Pair_First(
    std::tuple<ARGS...>&& argsPack,
    xref:BloombergLP/bslstl/Pair_IndexSequence.adoc[BloombergLP::bslstl::Pair_IndexSequence<I...>] indices);
----

== Description

Construct the `first` member of a `pair`, forwarding in order the elements in the specified `argsPack` to the corresponding constructor of (template parameter) `TYPE`. The length of the `argsPack` is equal to the length of the specified (template parameter pack) `I...` and passed to the constructor via the `Pair_IndexSequence` object.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *argsPack*
| tuple of arguments forwarded to the constructor of `TYPE`
| *indices*
| index sequence enumerating the elements of `argsPack`
|===


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