Re: [Boost-users] [lambda] newbie: lambda to help in std::accumulate

Subject: Re: [Boost-users] [lambda] newbie: lambda to help in std::accumulate
From: Stuart Dootson (stuart.dootson_at_[hidden])
Date: 2009-01-25 08:51:51

2009/1/25 Micha³ Nowotka <mmmnow_at_[hidden]>:
> I want to compute sum of logarithms so i wrote:
>
> #include <cmath>
>
> double evaluate(const vector<double>& win_probabls)
> {
>        return accumulate (win_probabls.begin(), win_probabls.end(), 0,
> lambda::_1 + log(lambda::_2) );
> }
>
> but this code doesn't compile. Does anyone know why?
>
> --
>
> Micha³ Nowotka

'log' is a function, so a call to it in a lambda expression has to be
within a bind expression:

double evaluate(const std::vector<double>& win_probabls)
{
   using namespace boost::lambda;
   return accumulate (win_probabls.begin(), win_probabls.end(), 0,
   _1 + bind(log, _2) );
}

Stuart Dootson