Purpse:
Given:
  class Person
  {
   public :
   // Some interface...
    const std::string& GetName ( ) const ;
   // ...some more definition
  } ;
  typedef vector < Person* >    PersonVector ;
  typedef PersonVector::iterator   PersonVecIter ;
  typedef PersonVector::const_iterator PersonVecConstIter ;

This library allows you to substitue the following functor code:

  struct LessPersonByName : public binary_function < PersonVecConstIter , PersonVecConstIter , bool >
  {
   bool operator ( ) (
      PersonVecConstIter inLHS ,
      PersonVecConstIter inRHS )
      { return inLHS->GetName ( ) < inRHS->GetName ( ) ; }
  }
  //...
  sort ( aPersonVec.begin ( ) ,
    aPersonVec.end ( ) ,
    LessPersonByName ( ) ) ;

With this:
  sort ( aPersonVec.begin ( ) ,
    aPersonVec.end ( ) ,
    LessMemberFunc ( &Person::GetName ) ) ;