using-declaration problem

[Dennis G. Faynberg]

Hi, I see a strange problem with g++, it does not recongnize
using-declaration when used to bring an operator into scope.

namespace X { using namespace std; string operator+(const string &, long); }

void f()
{
    using X::operator+; //this is where g++ tells me

    //there is a parse error before 'operator'

    (std::string)"Number " + 1L + ", take us out";
}

what is wrong here, I do not get it.

            Dennis

ps: using using-directive (eg. using namespace X;) is not an option in my
real life problem, this is just an
example of what essentially happening in real code, if you want to see real
code, its posted in this newsgroup (comp.lang.c++)
under heading "c++ namespaces, operators and visual c++, g++", but I have
not had much success with responses
there.