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///////////////////////////////////////////////////////////////////////////////
// value_accumulator.hpp
//
// Copyright 2005 Eric Niebler, Daniel Egloff. 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)
#ifndef BOOST_ACCUMULATORS_FRAMEWORK_ACCUMULATORS_VALUE_ACCUMULATOR_HPP_EAN_03_23_2006
#define BOOST_ACCUMULATORS_FRAMEWORK_ACCUMULATORS_VALUE_ACCUMULATOR_HPP_EAN_03_23_2006
#include <boost/mpl/always.hpp>
#include <boost/parameter/keyword.hpp>
#include <boost/accumulators/framework/depends_on.hpp> // for feature_tag
#include <boost/accumulators/framework/accumulator_base.hpp>
#include <boost/accumulators/framework/extractor.hpp>
namespace boost { namespace accumulators
{
namespace impl
{
//////////////////////////////////////////////////////////////////////////
// value_accumulator_impl
template<typename ValueType, typename Tag>
struct value_accumulator_impl
: accumulator_base
{
typedef ValueType result_type;
template<typename Args>
value_accumulator_impl(Args const &args)
: val(args[parameter::keyword<Tag>::get()])
{
}
result_type result(dont_care) const
{
return this->val;
}
private:
ValueType val;
};
} // namespace impl
namespace tag
{
//////////////////////////////////////////////////////////////////////////
// value_tag
template<typename Tag>
struct value_tag
{
};
//////////////////////////////////////////////////////////////////////////
// value
template<typename ValueType, typename Tag>
struct value
: depends_on<>
{
/// INTERNAL ONLY
///
typedef mpl::always<accumulators::impl::value_accumulator_impl<ValueType, Tag> > impl;
};
}
namespace extract
{
BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, value, (typename)(typename))
BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, value_tag, (typename))
}
using extract::value;
using extract::value_tag;
// Map all value<V,T> features to value_tag<T> so
// that values can be extracted using value_tag<T>
// without specifying the value type.
template<typename ValueType, typename Tag>
struct feature_of<tag::value<ValueType, Tag> >
: feature_of<tag::value_tag<Tag> >
{
};
}} // namespace boost::accumulators
#endif
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