| /////////////////////////////////////////////////////////////////////////////// |
| // 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 |