[#bsl-select1st-operator_call]
= xref:bsl.adoc[bsl]::xref:bsl/select1st.adoc[select1st]::operator()
:relfileprefix: ../../
:mrdocs:

Return a reference to the `first` member of the specified `x`.

== Synopsis

Declared in `<bslstp_exfunctional.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
PAIR::first_type const&
operator()(PAIR const& x) const;
----

== Return Value

const reference to `x.first`

== Parameters

[cols="1,4"]
|===
| Name| Description
| *x*
| pair from which to select the first member
|===


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