binding reference parameter causes error

[chenkai036]

Greetings, I'm studying bind1st/bind2nd in STL and encountered the following question.

I have a vector<int> and I want to print all elems in that vector in sequence. Here's my buggy code.

void print(int value, ostream& os)
{  os << value << " "; }

int main()
{
  vector<int> v;

  ... // initialize v, do not matter

  for_each(v.begin(), v.end(), bind2nd(ptr_fun(print), cout)));

  ... // other code, do not matter
}

The compiler complains that "reference to reference is illegal". I found it's the reference type in print that triggers the failure. However, for ostream, it's always passing-by-reference idiom when used as parameter, isn't it. So how should I correct the code? Thank you.

Although std::copy and boost::bind + boost::ref provide better solutions to my needs, I still curious at how to make the code work in bind2nd case.

copy(v.begin(), v.end(), ostream_iterator<int>(cout, " ")); // use copy
for_each(v.begin(), v.end(), boost::bind(print, _1, boost::ref(cout))); // use boost 

Best regards

CHEN Kai