/* The following code example is taken from the book * "C++ Templates - The Complete Guide" * by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002 * * (C) Copyright David Vandevoorde and Nicolai M. Josuttis 2002. * Permission to copy, use, modify, sell and distribute this software * is granted provided this copyright notice appears in all copies. * This software is provided "as is" without express or implied * warranty, and with no claim as to its suitability for any purpose. */#include "typeop.hpp" // return Nth value of variable duotemplate <int N, typename A, typename B> inlinetypename TypeOp<typename DuoT<N, Duo<A, B> >::ResultT>::RefTval(Duo<A, B>& d){    return DuoValue<N, Duo<A, B> >::get(d);}// return Nth value of constant duotemplate <int N, typename A, typename B> inlinetypename TypeOp<typename DuoT<N, Duo<A, B> >::ResultT>::RefConstTval(Duo<A, B> const& d){    return DuoValue<N, Duo<A, B> >::get(d);}