[#BloombergLP-bslstl-MapComparator-0d-operator_call-082d] = xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslstl.adoc[bslstl]::xref:BloombergLP/bslstl/MapComparator-0d.adoc[MapComparator]::operator() :relfileprefix: ../../../ :mrdocs: 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`. == 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); ---- [.small]#Created with https://www.mrdocs.com[MrDocs]#