///////////////////////////////////////////////////////////////////////////////
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// value_accumulator.hpp
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//
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// Copyright 2005 Eric Niebler, Daniel Egloff. Distributed under the Boost
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// Software License, Version 1.0. (See accompanying file
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// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_ACCUMULATORS_FRAMEWORK_ACCUMULATORS_VALUE_ACCUMULATOR_HPP_EAN_03_23_2006
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#define BOOST_ACCUMULATORS_FRAMEWORK_ACCUMULATORS_VALUE_ACCUMULATOR_HPP_EAN_03_23_2006
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#include <boost/mpl/always.hpp>
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#include <boost/parameter/keyword.hpp>
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#include <boost/accumulators/framework/depends_on.hpp> // for feature_tag
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#include <boost/accumulators/framework/accumulator_base.hpp>
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#include <boost/accumulators/framework/extractor.hpp>
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namespace boost { namespace accumulators
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{
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namespace impl
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{
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//////////////////////////////////////////////////////////////////////////
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// value_accumulator_impl
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template<typename ValueType, typename Tag>
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struct value_accumulator_impl
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: accumulator_base
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{
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typedef ValueType result_type;
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template<typename Args>
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value_accumulator_impl(Args const &args)
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: val(args[parameter::keyword<Tag>::instance])
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{
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}
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result_type result(dont_care) const
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{
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return this->val;
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}
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private:
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ValueType val;
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};
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} // namespace impl
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namespace tag
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{
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//////////////////////////////////////////////////////////////////////////
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// value_tag
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template<typename Tag>
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struct value_tag
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{
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};
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//////////////////////////////////////////////////////////////////////////
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// value
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template<typename ValueType, typename Tag>
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struct value
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: depends_on<>
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{
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/// INTERNAL ONLY
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///
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typedef mpl::always<accumulators::impl::value_accumulator_impl<ValueType, Tag> > impl;
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};
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}
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namespace extract
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{
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BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, value, (typename)(typename))
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BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, value_tag, (typename))
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}
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using extract::value;
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using extract::value_tag;
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// Map all value<V,T> features to value_tag<T> so
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// that values can be extracted using value_tag<T>
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// without specifying the value type.
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template<typename ValueType, typename Tag>
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struct feature_of<tag::value<ValueType, Tag> >
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: feature_of<tag::value_tag<Tag> >
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{
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};
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}} // namespace boost::accumulators
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#endif
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