ceph/src/boost/libs/accumulators/include/boost/accumulators/framework/accumulators/value_accumulator.hpp

   1 ///////////////////////////////////////////////////////////////////////////////
   2 // value_accumulator.hpp
   3 //
   4 //  Copyright 2005 Eric Niebler, Daniel Egloff. Distributed under the Boost
   5 //  Software License, Version 1.0. (See accompanying file
   6 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7
   8 #ifndef BOOST_ACCUMULATORS_FRAMEWORK_ACCUMULATORS_VALUE_ACCUMULATOR_HPP_EAN_03_23_2006
   9 #define BOOST_ACCUMULATORS_FRAMEWORK_ACCUMULATORS_VALUE_ACCUMULATOR_HPP_EAN_03_23_2006
  10
  11 #include <boost/mpl/always.hpp>
  12 #include <boost/parameter/keyword.hpp>
  13 #include <boost/accumulators/framework/depends_on.hpp> // for feature_tag
  14 #include <boost/accumulators/framework/accumulator_base.hpp>
  15 #include <boost/accumulators/framework/extractor.hpp>
  16
  17 namespace boost { namespace accumulators
  18 {
  19
  20 namespace impl
  21 {
  22
  23     //////////////////////////////////////////////////////////////////////////
  24     // value_accumulator_impl
  25     template<typename ValueType, typename Tag>
  26     struct value_accumulator_impl
  27       : accumulator_base
  28     {
  29         typedef ValueType result_type;
  30
  31         template<typename Args>
  32         value_accumulator_impl(Args const &args)
  33           : val(args[parameter::keyword<Tag>::get()])
  34         {
  35         }
  36
  37         result_type result(dont_care) const
  38         {
  39             return this->val;
  40         }
  41
  42     private:
  43         ValueType val;
  44     };
  45
  46 } // namespace impl
  47
  48 namespace tag
  49 {
  50     //////////////////////////////////////////////////////////////////////////
  51     // value_tag
  52     template<typename Tag>
  53     struct value_tag
  54     {
  55     };
  56
  57     //////////////////////////////////////////////////////////////////////////
  58     // value
  59     template<typename ValueType, typename Tag>
  60     struct value
  61       : depends_on<>
  62     {
  63         /// INTERNAL ONLY
  64         ///
  65         typedef mpl::always<accumulators::impl::value_accumulator_impl<ValueType, Tag> > impl;
  66     };
  67 }
  68
  69 namespace extract
  70 {
  71     BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, value, (typename)(typename))
  72     BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, value_tag, (typename))
  73 }
  74
  75 using extract::value;
  76 using extract::value_tag;
  77
  78 // Map all value<V,T> features to value_tag<T> so
  79 // that values can be extracted using value_tag<T>
  80 // without specifying the value type.
  81 template<typename ValueType, typename Tag>
  82 struct feature_of<tag::value<ValueType, Tag> >
  83   : feature_of<tag::value_tag<Tag> >
  84 {
  85 };
  86
  87 }} // namespace boost::accumulators
  88
  89 #endif