[CppAD] operator>>( istream , AD<double> )

[Norman Goldstein]

I would find it convenient to write code like:

#include <iostream>
CppAD::AD<double> x;
std::cin >> x;

but I get the error

//============ Error from compilier ====================
tcppad.cpp:70:14: error: cannot bind ‘std::istream {aka 
std::basic_istream<char>}’ lvalue to ‘std::basic_istream<char>&&’
In file included from 
/usr/lib/gcc/i686-redhat-linux/4.7.2/../../../../include/c++/4.7.2/iostream:41:0,
from /home/work/SRC/source/SVN_src/dev/src/test/tcppad.cpp:1:
/usr/lib/gcc/i686-redhat-linux/4.7.2/../../../../include/c++/4.7.2/istream:866:5: 
error: initializing argument 1 of ‘std::basic_istream<_CharT, _Traits>& 
std::operator>>(std::basic_istream<_CharT, _Traits>&&, _Tp&) [with 
_CharT = char; _Traits = std::char_traits<char>; _Tp = CppAD::AD<double>]’
//==============================================

Is there a header I should be using? Or is this code not a good idea?

I am using
g++ -std=c++0x ...

on Fedora 17, 32-bit, x86

Thank you.