[Boost-users] [foreach] boost_foreach_is_lightweight_proxy doesn't work

From: Raider (sraider_at_[hidden])
Date: 2007-07-23 13:22:23

Hi, i'm trying to modify rvalue container using Boost.ForEach:

#include <string>
#include <vector>
#include <boost/foreach.hpp>

typedef std::vector<std::string> vec;

inline boost::mpl::true_ *
boost_foreach_is_lightweight_proxy(vec *&, boost::foreach::tag)
{ return 0; }

vec GetVector()
{
     vec v;
     v.push_back("hello");
     v.push_back("world");
     return v;
}

int main()
{
     // compiles ok
     GetVector().push_back("oh god, it's writable!");

     // next line gives "unable to convert `const string' to `string&'"
     BOOST_FOREACH(std::string& String, GetVector())
         String.clear();

     return 0;
}

It doen't compiles (MCVC 8.0) - it looks like 
boost_foreach_is_lightweight_proxy is ignored. What's wrong?