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/Src/Dependencies/Boost/boost/accumulators/framework/accumulators/reference_accumulator.hpp

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 1///////////////////////////////////////////////////////////////////////////////
 2// reference_accumulator.hpp
 3//
 4//  Copyright 2005 Eric Niebler. 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_REFERENCE_ACCUMULATOR_HPP_EAN_03_23_2006
 9#define BOOST_ACCUMULATORS_FRAMEWORK_ACCUMULATORS_REFERENCE_ACCUMULATOR_HPP_EAN_03_23_2006
10
11#include <boost/ref.hpp>
12#include <boost/mpl/always.hpp>
13#include <boost/parameter/keyword.hpp>
14#include <boost/accumulators/framework/depends_on.hpp> // for feature_tag
15#include <boost/accumulators/framework/accumulator_base.hpp>
16#include <boost/accumulators/framework/extractor.hpp>
17
18namespace boost { namespace accumulators
19{
20
21namespace impl
22{
23    //////////////////////////////////////////////////////////////////////////
24    // reference_accumulator_impl
25    //
26    template<typename Referent, typename Tag>
27    struct reference_accumulator_impl
28      : accumulator_base
29    {
30        typedef Referent &result_type;
31
32        template<typename Args>
33        reference_accumulator_impl(Args const &args)
34          : ref(args[parameter::keyword<Tag>::get()])
35        {
36        }
37
38        result_type result(dont_care) const
39        {
40            return this->ref;
41        }
42
43    private:
44        reference_wrapper<Referent> ref;
45    };
46} // namespace impl
47
48namespace tag
49{
50    //////////////////////////////////////////////////////////////////////////
51    // reference_tag
52    template<typename Tag>
53    struct reference_tag
54    {
55    };
56
57    //////////////////////////////////////////////////////////////////////////
58    // reference
59    template<typename Referent, typename Tag>
60    struct reference
61      : depends_on<>
62    {
63        /// INTERNAL ONLY
64        ///
65        typedef mpl::always<accumulators::impl::reference_accumulator_impl<Referent, Tag> > impl;
66    };
67}
68
69namespace extract
70{
71    BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, reference, (typename)(typename))
72    BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, reference_tag, (typename))
73}
74
75using extract::reference;
76using extract::reference_tag;
77
78// Map all reference<V,T> features to reference_tag<T> so
79// that references can be extracted using reference_tag<T>
80// without specifying the referent type.
81template<typename ValueType, typename Tag>
82struct feature_of<tag::reference<ValueType, Tag> >
83  : feature_of<tag::reference_tag<Tag> >
84{
85};
86
87}} // namespace boost::accumulators
88
89#endif