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

   1 //---------------------------------------------------------------------------//
   2 // Copyright (c) 2013-2014 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_IDENTITY_HPP
  12 #define BOOST_COMPUTE_FUNCTIONAL_IDENTITY_HPP
  13
  14 namespace boost {
  15 namespace compute {
  16 namespace detail {
  17
  18 template<class T, class Arg>
  19 struct invoked_identity
  20 {
  21     typedef T result_type;
  22
  23     invoked_identity(const Arg &arg)
  24         : m_arg(arg)
  25     {
  26     }
  27
  28     Arg m_arg;
  29 };
  30
  31 } // end detail namespace
  32
  33 /// Identity function which simply returns its input.
  34 ///
  35 /// For example, to directly copy values using the transform() algorithm:
  36 /// \code
  37 /// transform(input.begin(), input.end(), output.begin(), identity<int>(), queue);
  38 /// \endcode
  39 ///
  40 /// \see \ref as "as<T>", \ref convert "convert<T>"
  41 template<class T>
  42 class identity
  43 {
  44 public:
  45     /// Identity function result type.
  46     typedef T result_type;
  47
  48     /// Creates a new identity function.
  49     identity()
  50     {
  51     }
  52
  53     /// \internal_
  54     template<class Arg>
  55     detail::invoked_identity<T, Arg> operator()(const Arg &arg) const
  56     {
  57         return detail::invoked_identity<T, Arg>(arg);
  58     }
  59 };
  60
  61 } // end compute namespace
  62 } // end boost namespace
  63
  64 #endif // BOOST_COMPUTE_FUNCTIONAL_IDENTITY_HPP