Boost :: Lambda中的ref（）？

Question

What is the equivalent of Boost::Phoenix's ref in Boost::Lambda? I can't find it in the online docs.

#include <algorithm>
#include <string>
#include <boost/lambda/bind.hpp>
using namespace boost::lambda;

int main()
{
    std::string a, b;
    std::for_each(b.begin(), b.end(), ref(a) += _1);  // how do I do this?
}

boost::ref and boost::lambda::var don't seem to work (they don't have the operator overloads, apparently).

Answer 1

D'oh, I just figured it out...

Just #include <boost/lambda/lambda.hpp> and then var will work!