[#bsl-unordered_map-02b-at-07]
= xref:bsl.adoc[bsl]::xref:bsl/unordered_map-02b.adoc[unordered&lowbar;map]::at
:relfileprefix: ../../
:mrdocs:

Return a modifiable reference to the mapped value for `key`&period;

== Synopsis

Declared in `&lt;bslstl&lowbar;unorderedmap&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template&lt;class LOOKUP&lowbar;KEY&gt;
add&lowbar;lvalue&lowbar;reference&lt;VALUE&gt;::type
at(LOOKUP&lowbar;KEY const& key)
requires BloombergLP&colon;&colon;bslmf&colon;&colon;IsTransparentPredicate&lt;HASH, LOOKUP&lowbar;KEY&gt;&colon;&colon;value
        &amp;&amp; BloombergLP&colon;&colon;bslmf&colon;&colon;IsTransparentPredicate&lt;EQUAL,LOOKUP&lowbar;KEY&gt;&colon;&colon;value;
----

== Description

Return a reference providing modifiable access to the mapped&hyphen;value associated with a key that is equivalent to the specified `key`, if such an entry exists&semi; otherwise, throw a `std&colon;&colon;out&lowbar;of&lowbar;range` exception&period; Note that this method may also throw a different kind of exception if the (user&hyphen;supplied) comparator throws&period;

Note&colon; implemented inline due to Sun CC compilation error

== Return Value

modifiable reference to the mapped value

== Parameters

[cols="1,4"]
|===
| Name| Description
| *key*
| key whose mapped value is accessed
|===


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