[#BloombergLP-bslstl-MapComparator-operator_call-082d]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslstl.adoc[bslstl]::xref:BloombergLP/bslstl/MapComparator.adoc[MapComparator]::operator()
:relfileprefix: ../../../
:mrdocs:

Return whether the key stored in `lhs` is ordered before `rhs`.

== Synopsis

Declared in `<bslstl_mapcomparator.h>`

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

== Description

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

== Return Value

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

== Parameters

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


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