Ok, i now I've corrected my method to: double evaluate(const vector<double>& win_probabls) { return accumulate (win_probabls.begin(), win_probabls.end(), 0, lambda::_1 + lambda::bind(log, lambda::_2) ); } and got following warning (which i can't understand): c:\program files\boost\boost_1_36_0\boost\lambda\detail\lambda_traits.hpp(389) : warning C4180: qualifier applied to function type has no meaning; ignored c:\program files\boost\boost_1_36_0\boost\lambda\detail\lambda_traits.hpp(458) : see reference to class template instantiation 'boost::lambda::detail::bind_traits<T>' being compiled with [ T=double (double) ] c:\users\kott\documents\visual studio 2008\projects\mbi\implementation\src\main.cpp(613) : see reference to class template instantiation 'boost::lambda::detail::bind_tuple_mapper<T0,T1,T2,T3,T4,T5,T6,T7,T8,T9>' being compiled with [ T0=double (double), T1=boost::lambda::placeholder2_type, T2=boost::tuples::null_type, T3=boost::tuples::null_type, T4=boost::tuples::null_type, T5=boost::tuples::null_type, T6=boost::tuples::null_type, T7=boost::tuples::null_type, T8=boost::tuples::null_type, T9=boost::tuples::null_type ] c:\users\kott\documents\visual studio 2008\projects\mbi\implementation\src\main.cpp(698) : warning C4267: 'initializing' : conversion from 'size_t' to 'const int', possible loss of data c:\program files\microsoft visual studio 9.0\vc\include\numeric(45) : warning C4244: '=' : conversion from 'double' to 'int', possible loss of data c:\program files\microsoft visual studio 9.0\vc\include\numeric(54) : see reference to function template instantiation '_Ty std::_Accumulate<std::_Vector_const_iterator<double,_Alloc>,_Ty,_Fn2>(_InIt,_InIt,_Ty,_Fn2)' being compiled with [ _Ty=int, _Alloc=std::allocator<double>, _Fn2=boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::arithmetic_action<boost::lambda::plus_action>,boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::placeholder<1>>,boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<2,boost::lambda::function_action<2,double>>,boost::tuples::tuple<double (__cdecl &)(double),const boost::lambda::lambda_functor<boost::lambda::placeholder<2>>,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type>>>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>>>, _InIt=std::_Vector_const_iterator<double,std::allocator<double>> ] c:\users\kott\documents\visual studio 2008\projects\mbi\implementation\src\main.cpp(613) : see reference to function template instantiation '_Ty std::accumulate<std::_Vector_const_iterator<double,_Alloc>,int,boost::lambda::lambda_functor<T>>(_InIt,_InIt,_Ty,_Fn2)' being compiled with [ _Ty=int, _Alloc=std::allocator<double>, T=boost::lambda::lambda_functor_base<boost::lambda::arithmetic_action<boost::lambda::plus_action>,boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::placeholder<1>>,boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<2,boost::lambda::function_action<2,double>>,boost::tuples::tuple<double (__cdecl &)(double),const boost::lambda::lambda_functor<boost::lambda::placeholder<2>>,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type>>>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>>, _InIt=std::_Vector_const_iterator<double,std::allocator<double>>, _Fn2=boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::arithmetic_action<boost::lambda::plus_action>,boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::placeholder<1>>,boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<2,boost::lambda::function_action<2,double>>,boost::tuples::tuple<double (__cdecl &)(double),const boost::lambda::lambda_functor<boost::lambda::placeholder<2>>,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type,boost::lambda::detail::bind_traits<boost::tuples::null_type>::type>>>,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type,boost::tuples::null_type>>> ] what I'm doing wrong?