ceph/src/boost/libs/compute/include/boost/compute/lambda/placeholders.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_LAMBDA_PLACEHOLDERS_HPP
  12 #define BOOST_COMPUTE_LAMBDA_PLACEHOLDERS_HPP
  13
  14 #include <boost/mpl/has_xxx.hpp>
  15
  16 #include <boost/compute/lambda/context.hpp>
  17 #include <boost/compute/lambda/result_of.hpp>
  18
  19 namespace boost {
  20 namespace compute {
  21 namespace lambda {
  22
  23 namespace mpl = boost::mpl;
  24 namespace proto = boost::proto;
  25
  26 // lambda placeholders
  27 expression<proto::terminal<placeholder<0> >::type> const _1;
  28 expression<proto::terminal<placeholder<1> >::type> const _2;
  29 expression<proto::terminal<placeholder<2> >::type> const _3;
  30
  31 namespace detail {
  32
  33 BOOST_MPL_HAS_XXX_TRAIT_DEF(result_type)
  34
  35 template<class T, bool HasResultType>
  36 struct terminal_type_impl;
  37
  38 template<class T>
  39 struct terminal_type_impl<T, true>
  40 {
  41     typedef typename T::result_type type;
  42 };
  43
  44 template<class T>
  45 struct terminal_type_impl<T, false>
  46 {
  47     typedef T type;
  48 };
  49
  50 template<class T>
  51 struct terminal_type
  52 {
  53     typedef typename terminal_type_impl<T, has_result_type<T>::value>::type type;
  54 };
  55
  56 } // end detail namespace
  57
  58 // result_of placeholders
  59 template<class Args>
  60 struct result_of<expression<proto::terminal<placeholder<0> >::type>, Args, proto::tag::terminal>
  61 {
  62     typedef typename boost::tuples::element<0, Args>::type arg_type;
  63
  64     typedef typename detail::terminal_type<arg_type>::type type;
  65 };
  66
  67 template<class Args>
  68 struct result_of<expression<proto::terminal<placeholder<1> >::type>, Args, proto::tag::terminal>
  69 {
  70     typedef typename boost::tuples::element<1, Args>::type arg_type;
  71
  72     typedef typename detail::terminal_type<arg_type>::type type;
  73 };
  74
  75 template<class Args>
  76 struct result_of<expression<proto::terminal<placeholder<2> >::type>, Args, proto::tag::terminal>
  77 {
  78     typedef typename boost::tuples::element<2, Args>::type arg_type;
  79
  80     typedef typename detail::terminal_type<arg_type>::type type;
  81 };
  82
  83 } // end lambda namespace
  84
  85 // lift lambda placeholders up to the boost::compute namespace
  86 using lambda::_1;
  87 using lambda::_2;
  88 using lambda::_3;
  89
  90 } // end compute namespace
  91 } // end boost namespace
  92
  93 #endif // BOOST_COMPUTE_LAMBDA_PLACEHOLDERS_HPP