/Src/Dependencies/Boost/boost/accumulators/framework/accumulators/external_accumulator.hpp
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- ///////////////////////////////////////////////////////////////////////////////
- // external_accumulator.hpp
- //
- // Copyright 2005 Eric Niebler. 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_EXTERNAL_ACCUMULATOR_HPP_EAN_01_12_2005
- #define BOOST_ACCUMULATORS_FRAMEWORK_ACCUMULATORS_EXTERNAL_ACCUMULATOR_HPP_EAN_01_12_2005
- #include <boost/mpl/placeholders.hpp>
- #include <boost/parameter/keyword.hpp>
- #include <boost/accumulators/framework/extractor.hpp>
- #include <boost/accumulators/framework/depends_on.hpp> // for feature_tag
- #include <boost/accumulators/framework/accumulator_base.hpp>
- #include <boost/accumulators/framework/accumulators/reference_accumulator.hpp>
- namespace boost { namespace accumulators { namespace impl
- {
- //////////////////////////////////////////////////////////////////////////
- // external_impl
- /// INTERNAL ONLY
- ///
- template<typename Accumulator, typename Tag>
- struct external_impl
- : accumulator_base
- {
- typedef typename Accumulator::result_type result_type;
- typedef typename detail::feature_tag<Accumulator>::type feature_tag;
- external_impl(dont_care) {}
- template<typename Args>
- result_type result(Args const &args) const
- {
- return this->extract_(args, args[parameter::keyword<Tag>::get() | 0]);
- }
- private:
- template<typename Args>
- static result_type extract_(Args const &args, int)
- {
- // No named parameter passed to the extractor. Maybe the external
- // feature is held by reference<>.
- extractor<feature_tag> extract;
- return extract(accumulators::reference_tag<Tag>(args));
- }
- template<typename Args, typename AccumulatorSet>
- static result_type extract_(Args const &, AccumulatorSet const &acc)
- {
- // OK, a named parameter for this external feature was passed to the
- // extractor, so use that.
- extractor<feature_tag> extract;
- return extract(acc);
- }
- };
- } // namespace impl
- namespace tag
- {
- //////////////////////////////////////////////////////////////////////////
- // external
- template<typename Feature, typename Tag, typename AccumulatorSet>
- struct external
- : depends_on<reference<AccumulatorSet, Tag> >
- {
- typedef
- accumulators::impl::external_impl<
- detail::to_accumulator<Feature, mpl::_1, mpl::_2>
- , Tag
- >
- impl;
- };
- template<typename Feature, typename Tag>
- struct external<Feature, Tag, void>
- : depends_on<>
- {
- typedef
- accumulators::impl::external_impl<
- detail::to_accumulator<Feature, mpl::_1, mpl::_2>
- , Tag
- >
- impl;
- };
- }
- // for the purposes of feature-based dependency resolution,
- // external_accumulator<Feature, Tag> provides the same feature as Feature
- template<typename Feature, typename Tag, typename AccumulatorSet>
- struct feature_of<tag::external<Feature, Tag, AccumulatorSet> >
- : feature_of<Feature>
- {
- };
- // Note: Usually, the extractor is pulled into the accumulators namespace with
- // a using directive, not the tag. But the external<> feature doesn't have an
- // extractor, so we can put the external tag in the accumulators namespace
- // without fear of a name conflict.
- using tag::external;
- }} // namespace boost::accumulators
- #endif