ceph/src/boost/boost/compute/functional/get.hpp

   1 //---------------------------------------------------------------------------//
   2 // Copyright (c) 2013 Kyle Lutz <kyle.r.lutz@gmail.com>
   3 //
   4 // Distributed under the Boost Software License, Version 1.0
   5 // See accompanying file LICENSE_1_0.txt or copy at
   6 // http://www.boost.org/LICENSE_1_0.txt
   7 //
   8 // See http://boostorg.github.com/compute for more information.
   9 //---------------------------------------------------------------------------//
  10
  11 #ifndef BOOST_COMPUTE_FUNCTIONAL_GET_HPP
  12 #define BOOST_COMPUTE_FUNCTIONAL_GET_HPP
  13
  14 #include <cstddef>
  15
  16 #include <boost/compute/types/fundamental.hpp>
  17 #include <boost/compute/type_traits/scalar_type.hpp>
  18
  19 namespace boost {
  20 namespace compute {
  21 namespace detail {
  22
  23 // meta-function returning the result type for get<N>()
  24 template<size_t N, class Arg>
  25 struct get_result_type
  26 {
  27     typedef typename scalar_type<Arg>::type type;
  28 };
  29
  30 template<size_t N, class Arg, class T>
  31 struct invoked_get
  32 {
  33     typedef typename get_result_type<N, T>::type result_type;
  34
  35     invoked_get(const Arg &arg)
  36         : m_arg(arg)
  37     {
  38     }
  39
  40     Arg m_arg;
  41 };
  42
  43 } // end detail namespace
  44
  45 /// Returns the \c N'th element of an aggregate type (e.g. scalarN,
  46 /// pair, tuple, etc.).
  47 ///
  48 /// \see \ref field "field<T>"
  49 template<size_t N>
  50 struct get
  51 {
  52     /// \internal_
  53     template<class> struct result;
  54
  55     /// \internal_
  56     template<class F, class Arg>
  57     struct result<F(Arg)>
  58     {
  59         typedef typename detail::get_result_type<N, Arg>::type type;
  60     };
  61
  62     template<class Arg>
  63     detail::invoked_get<
  64         N, Arg, typename boost::remove_cv<typename Arg::result_type>::type
  65     > operator()(const Arg &arg) const
  66     {
  67         typedef typename boost::remove_cv<typename Arg::result_type>::type T;
  68
  69         return detail::invoked_get<N, Arg, T>(arg);
  70     }
  71 };
  72
  73 } // end compute namespace
  74 } // end boost namespace
  75
  76 #endif // BOOST_COMPUTE_FUNCTIONAL_GET_HPP