Chris@16: ///////////////////////////////////////////////////////////////////////////////
Chris@16: /// \file at.hpp
Chris@16: /// Proto callables Fusion at
Chris@16: //
Chris@16: //  Copyright 2010 Eric Niebler. Distributed under the Boost
Chris@16: //  Software License, Version 1.0. (See accompanying file
Chris@16: //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_PROTO_FUNCTIONAL_FUSION_AT_HPP_EAN_11_27_2010
Chris@16: #define BOOST_PROTO_FUNCTIONAL_FUSION_AT_HPP_EAN_11_27_2010
Chris@16: 
Chris@16: #include <boost/type_traits/add_const.hpp>
Chris@16: #include <boost/type_traits/remove_const.hpp>
Chris@16: #include <boost/type_traits/remove_reference.hpp>
Chris@16: #include <boost/fusion/include/at.hpp>
Chris@16: #include <boost/proto/proto_fwd.hpp>
Chris@16: 
Chris@16: namespace boost { namespace proto { namespace functional
Chris@16: {
Chris@16:     /// \brief A PolymorphicFunctionObject type that invokes the
Chris@16:     /// \c fusion::at() accessor on its argument.
Chris@16:     ///
Chris@16:     /// A PolymorphicFunctionObject type that invokes the
Chris@16:     /// \c fusion::at() accessor on its argument.
Chris@16:     struct at
Chris@16:     {
Chris@16:         BOOST_PROTO_CALLABLE()
Chris@16: 
Chris@16:         template<typename Sig>
Chris@16:         struct result;
Chris@16: 
Chris@16:         template<typename This, typename Seq, typename N>
Chris@16:         struct result<This(Seq, N)>
Chris@16:           : fusion::result_of::at<
Chris@16:                 typename boost::remove_reference<Seq>::type
Chris@16:               , typename boost::remove_const<typename boost::remove_reference<N>::type>::type
Chris@16:             >
Chris@16:         {};
Chris@16: 
Chris@16:         template<typename Seq, typename N>
Chris@16:         typename fusion::result_of::at<Seq, N>::type
Chris@16:         operator ()(Seq &seq, N const & BOOST_PROTO_DISABLE_IF_IS_CONST(Seq)) const
Chris@16:         {
Chris@16:             return fusion::at<N>(seq);
Chris@16:         }
Chris@16: 
Chris@16:         template<typename Seq, typename N>
Chris@16:         typename fusion::result_of::at<Seq const, N>::type
Chris@16:         operator ()(Seq const &seq, N const &) const
Chris@16:         {
Chris@16:             return fusion::at<N>(seq);
Chris@16:         }
Chris@16:     };
Chris@16: }}}
Chris@16: 
Chris@16: #endif