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

This component‐private `class` holds the `first` data member of a `pair` and constructs it appropriately. Note the partial specializations below for the cases that (template parameter) 'TYPE' is a reference.

== Synopsis

Declared in `<bslstl_pair.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class TYPE>
struct Pair_First;
----

== Protected Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/Pair_First-00/2constructor-0a7.adoc[`Pair_First`]         [.small]#[constructor]#
| Constructors
|===


== Protected Data Members

[cols="1,4"]
|===
| Name| Description
| xref:bsl/Pair_First-00/first.adoc[`first`] 
| First element of the pair.
|===


== Specializations

[cols="1,4"]
|===
| Name| Description
| xref:bsl/Pair_First-02.adoc[`Pair_First<TYPE&>`] 
| This component‐private `class` holds the `first` data member of a `pair` when that member is an lvalue‐reference. Note that the C++ Standard defines the assignment operator to assign through the reference in this case, where the implicitly declared assignment operator would be deleted.
| xref:bsl/Pair_First-09.adoc[`Pair_First<TYPE&&>`] 
| This component‐private `class` holds the `first` data member of a `pair` when that member is an rvalue‐reference. Note that the C++ Standard defines the assignment operator to assign through the reference in this case, where the implicitly declared assignment operator would be deleted.
|===


== Derived Classes

[cols="1,4"]
|===
| Name| Description
| xref:bsl/pair-0b.adoc[`pair`] 
| The class template `pair` provides a pair of public data members, `first` and `second`, of type `T1` and `T2` respectively. If either `T1` or `T2` uses `bslma::Allocator` for memory management, then provide an optional `bslma::Allocator` argument for each constructor, to be passed through to the constructors of `first` and/or `second` as appropriate. The interface to this class is identical to the standard `std::pair` except for the addition of the allocators. Note that the implementation of this class provides `first` and `second` through multiple base classes in order to simplify construction of each member when allowing for the various rules for passing allocators in C++11.
|===


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