[#BloombergLP-bslstl-MapComparator-operator_call-0829]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslstl.adoc[bslstl]::xref:BloombergLP/bslstl/MapComparator.adoc[MapComparator]::operator()
:relfileprefix: ../../../
:mrdocs:

Return whether `lhs` is ordered before the key stored in `rhs`&period;

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template&lt;class LOOKUP&lowbar;KEY&gt;
bool
operator()(
    LOOKUP&lowbar;KEY const& lhs,
    xref:BloombergLP/bslalg/RbTreeNode.adoc[bslalg::RbTreeNode] const& rhs) const;
----

== Description

Return `true` if the specified `lhs` is less than (ordered before, according to the comparator held by this object) `value()&period;first` of the specified `rhs` after being cast to `NodeType`, and `false` otherwise&period; The behavior is undefined unless `rhs` can be safely cast to `NodeType`&period;

== Return Value

`true` if `lhs` is ordered before the key in `rhs`, and `false` otherwise

== Parameters

[cols="1,4"]
|===
| Name| Description
| *lhs*
| lookup key compared against the node&apos;s key
| *rhs*
| tree node whose key is compared to `lhs`
|===


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