ceph/src/boost/boost/compute/functional/field.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_FIELD_HPP
  12 #define BOOST_COMPUTE_FUNCTIONAL_FIELD_HPP
  13
  14 #include <string>
  15
  16 namespace boost {
  17 namespace compute {
  18 namespace detail {
  19
  20 template<class T, class Arg>
  21 struct invoked_field
  22 {
  23     typedef T result_type;
  24
  25     invoked_field(const Arg &arg, const std::string &field)
  26         : m_arg(arg),
  27           m_field(field)
  28     {
  29     }
  30
  31     Arg m_arg;
  32     std::string m_field;
  33 };
  34
  35 } // end detail namespace
  36
  37 /// Returns the named field from a value.
  38 ///
  39 /// The template-type \c T specifies the field's value type. Note
  40 /// that the value type must match the actual type of the field
  41 /// otherwise runtime compilation or logic errors may occur.
  42 ///
  43 /// For example, to access the \c second field in a
  44 /// \c std::pair<int, float> object:
  45 /// \code
  46 /// field<float>("second");
  47 /// \endcode
  48 ///
  49 /// This can also be used with vector types to access individual
  50 /// components as well as perform swizzle operations.
  51 ///
  52 /// For example, to access the first and third components of an
  53 /// \c int vector type (e.g. \c int4):
  54 /// \code
  55 /// field<int2_>("xz");
  56 /// \endcode
  57 ///
  58 /// \see \ref get "get<N>"
  59 template<class T>
  60 class field
  61 {
  62 public:
  63     /// Result type.
  64     typedef T result_type;
  65
  66     /// Creates a new field functor with \p field.
  67     field(const std::string &field)
  68         : m_field(field)
  69     {
  70     }
  71
  72     /// \internal_
  73     template<class Arg>
  74     detail::invoked_field<T, Arg> operator()(const Arg &arg) const
  75     {
  76         return detail::invoked_field<T, Arg>(arg, m_field);
  77     }
  78
  79 private:
  80     std::string m_field;
  81 };
  82
  83 } // end compute namespace
  84 } // end boost namespace
  85
  86 #endif // BOOST_COMPUTE_FUNCTIONAL_FIELD_HPP