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3rdparty/boost_1_81_0/boost/compute/lambda/placeholders.hpp 2.44 KB
63e88f80   Hu Chunming   提交三方库
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  //---------------------------------------------------------------------------//
  // Copyright (c) 2013 Kyle Lutz <kyle.r.lutz@gmail.com>
  //
  // Distributed under the Boost Software License, Version 1.0
  // See accompanying file LICENSE_1_0.txt or copy at
  // http://www.boost.org/LICENSE_1_0.txt
  //
  // See http://boostorg.github.com/compute for more information.
  //---------------------------------------------------------------------------//
  
  #ifndef BOOST_COMPUTE_LAMBDA_PLACEHOLDERS_HPP
  #define BOOST_COMPUTE_LAMBDA_PLACEHOLDERS_HPP
  
  #include <boost/mpl/has_xxx.hpp>
  
  #include <boost/compute/lambda/context.hpp>
  #include <boost/compute/lambda/result_of.hpp>
  
  namespace boost {
  namespace compute {
  namespace lambda {
  
  namespace mpl = boost::mpl;
  namespace proto = boost::proto;
  
  // lambda placeholders
  expression<proto::terminal<placeholder<0> >::type> const _1;
  expression<proto::terminal<placeholder<1> >::type> const _2;
  expression<proto::terminal<placeholder<2> >::type> const _3;
  
  namespace detail {
  
  BOOST_MPL_HAS_XXX_TRAIT_DEF(result_type)
  
  template<class T, bool HasResultType>
  struct terminal_type_impl;
  
  template<class T>
  struct terminal_type_impl<T, true>
  {
      typedef typename T::result_type type;
  };
  
  template<class T>
  struct terminal_type_impl<T, false>
  {
      typedef T type;
  };
  
  template<class T>
  struct terminal_type
  {
      typedef typename terminal_type_impl<T, has_result_type<T>::value>::type type;
  };
  
  } // end detail namespace
  
  // result_of placeholders
  template<class Args>
  struct result_of<expression<proto::terminal<placeholder<0> >::type>, Args, proto::tag::terminal>
  {
      typedef typename boost::tuples::element<0, Args>::type arg_type;
  
      typedef typename detail::terminal_type<arg_type>::type type;
  };
  
  template<class Args>
  struct result_of<expression<proto::terminal<placeholder<1> >::type>, Args, proto::tag::terminal>
  {
      typedef typename boost::tuples::element<1, Args>::type arg_type;
  
      typedef typename detail::terminal_type<arg_type>::type type;
  };
  
  template<class Args>
  struct result_of<expression<proto::terminal<placeholder<2> >::type>, Args, proto::tag::terminal>
  {
      typedef typename boost::tuples::element<2, Args>::type arg_type;
  
      typedef typename detail::terminal_type<arg_type>::type type;
  };
  
  } // end lambda namespace
  
  // lift lambda placeholders up to the boost::compute namespace
  using lambda::_1;
  using lambda::_2;
  using lambda::_3;
  
  } // end compute namespace
  } // end boost namespace
  
  #endif // BOOST_COMPUTE_LAMBDA_PLACEHOLDERS_HPP