lambda vs pure virtual functions

[sw_creator]

Hello all !
i tried to complile this code:
-----------------------
namespace Filter{

class ResultType {...};
class SubExpression
{
public:
  virtual ResultType Result()=0;
};
typedef boost::shared_ptr<SubExpression> SPtrSubExpression;
............
void F()
{
   namespace la=boost::lambda;
   ResultType r;
   vector<SPtrSubExpression> v; 
..................................
   vector<SPtrSubExpression>::const_iterator
i=find_if(v.begin(), v.end(), 
        la::bind(&SubExpression::Result, *la::_1)==r);
}

}
-------------------------
and I received error:

c:\Program
Files\boost-1-32-0\boost\tuple\detail\tuple_basic.hpp(419):
error C2259: 'Filter::SubExpression' : cannot
instantiate abstract class

complier :VC++ 7.1
boost 1.32.0

what's wrong?
thanks.