LM>class A
LM>{
LM>public:
LM> long ID_;
LM> ....
LM>};

LM>std::vector<A> x;
LM>

#include "stdafx.h"
#include <boost/bind.hpp>
#include <conio.h>
#include <vector>
#include <algorithm>
#include <functional>

class A
{
    long ID_;
public:
  A(long ID_):ID_(ID_){};

  friend bool operator == (const A& lhs, const A& rhs)
  {
      return(lhs.ID_ == rhs.ID_);
  }

};



int _tmain(int argc, _TCHAR* argv[])
{
    std::vector<A> x;
    x.push_back(A(21));
    x.push_back(A(12));
    x.push_back(A(15));
    x.push_back(A(32));
    

    std::vector<A>::iterator pos =  
        std::find_if(x.begin(),x.end(), boost::bind(std::equal_to<A>(),_1,15));

    std::cout << distance(x.begin(),pos)+1 << std::endl;

    getch();

    return 0;
}

B>  friend bool operator == (const A& lhs, const A& rhs)
B>  {
B>      return(lhs.ID_ == rhs.ID_);
B>  }
...
B>    std::vector<A>::iterator pos =  
B>        std::find_if(x.begin(),x.end(), boost::bind(std::equal_to<A>(),_1,15));
B>

    std::find_if( x.begin(), x.end(), boost::bind( std::equal_to<int>(), boost::bind( &A::id_, _1 ), 15 ) );

    std::find_if( x.begin(), x.end(), boost::bind( &A::id_, _1 ) == 15 );