1///////////////////////////////////////////////////////////////////////////////
2/// \file at.hpp
3/// Proto callables Fusion at
4//
5// Copyright 2010 Eric Niebler. Distributed under the Boost
6// Software License, Version 1.0. (See accompanying file
7// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
8
9#ifndef BOOST_PROTO_FUNCTIONAL_FUSION_AT_HPP_EAN_11_27_2010
10#define BOOST_PROTO_FUNCTIONAL_FUSION_AT_HPP_EAN_11_27_2010
11
12#include <boost/type_traits/add_const.hpp>
13#include <boost/type_traits/remove_const.hpp>
14#include <boost/type_traits/remove_reference.hpp>
15#include <boost/fusion/include/at.hpp>
16#include <boost/proto/proto_fwd.hpp>
17
18namespace boost { namespace proto { namespace functional
19{
20 /// \brief A PolymorphicFunctionObject type that invokes the
21 /// \c fusion::at() accessor on its argument.
22 ///
23 /// A PolymorphicFunctionObject type that invokes the
24 /// \c fusion::at() accessor on its argument.
25 struct at
26 {
27 BOOST_PROTO_CALLABLE()
28
29 template<typename Sig>
30 struct result;
31
32 template<typename This, typename Seq, typename N>
33 struct result<This(Seq, N)>
34 : fusion::result_of::at<
35 typename boost::remove_reference<Seq>::type
36 , typename boost::remove_const<typename boost::remove_reference<N>::type>::type
37 >
38 {};
39
40 template<typename Seq, typename N>
41 typename fusion::result_of::at<Seq, N>::type
42 operator ()(Seq &seq, N const & BOOST_PROTO_DISABLE_IF_IS_CONST(Seq)) const
43 {
44 return fusion::at<N>(seq);
45 }
46
47 template<typename Seq, typename N>
48 typename fusion::result_of::at<Seq const, N>::type
49 operator ()(Seq const &seq, N const &) const
50 {
51 return fusion::at<N>(seq);
52 }
53 };
54}}}
55
56#endif
57