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