BOOST_PHOENIX_ADAPT_FUNCTION causes invalid template error

Question

I am trying to create a lazy function from a template function following the Boost::phoenix documentation. The code looks like this

#include <iostream>

#include <boost/phoenix/core.hpp>
#include <boost/phoenix/function.hpp>
#include <boost/phoenix/operator.hpp>
#include <boost/phoenix/statement.hpp>
#include <boost/phoenix/object.hpp>
#include <boost/phoenix/function/adapt_function.hpp>
#include <boost/phoenix/core/argument.hpp>

using namespace boost;
using namespace boost::phoenix;

namespace demo
{
     bool func(double a,double b)
     {
         return bool(a > b);
     }
}

BOOST_PHOENIX_ADAPT_FUNCTION( bool , func , demo::func , 2)

int main(int argc,char **argv)
{
     namespace pl = boost::phoenix::placeholders;
     auto comperator = func(pl::arg1,pl::arg2);
     std::cout<<comperator(1.2,12.4)<<std::endl;
     std::cout<<comperator(0.5,0.1)<<std::endl;
}

This is virtually one of the examples from the BOOST documentation. Storing this file as mk_lazy1.cpp and try to compile gives

$ g++ -omk_lazy1 mk_lazy1.cpp                 
mk_lazy1.cpp:26:1: error: template argument 1 is invalid      
mk_lazy1.cpp:26:1: error: expected identifier before ‘::’ token  
mk_lazy1.cpp:26:1: error: expected initializer before ‘const’ 
mk_lazy1.cpp: In function ‘int main(int, char**)’:
mk_lazy1.cpp:31:10: error: ‘comperator’ does not name a type    
mk_lazy1.cpp:32:35: error: ‘comperator’ was not declared in this scope   

I use gcc-4.7 on a Debian testing system. An honestly I am a bit lost as I have absolutely no idea what is wrong here (as I said, this is virtually a word by word copy of one of the examples provided by the Boost documentation).

Does anyone have a good idea?

Answer 1

Remove using namespaces and all will work fine. Or write using namespaces AFTER adapt macro and all will work fine too. Or put macro into unnamed namespace.