1 /////////////////////////////////////////////////////////////////////////////// 2 // value_accumulator.hpp 3 // 4 // Copyright 2005 Eric Niebler, Daniel Egloff. Distributed under the Boost 5 // Software License, Version 1.0. (See accompanying file 6 // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 7 8 #ifndef BOOST_ACCUMULATORS_FRAMEWORK_ACCUMULATORS_VALUE_ACCUMULATOR_HPP_EAN_03_23_2006 9 #define BOOST_ACCUMULATORS_FRAMEWORK_ACCUMULATORS_VALUE_ACCUMULATOR_HPP_EAN_03_23_2006 10 11 #include <boost/mpl/always.hpp> 12 #include <boost/parameter/keyword.hpp> 13 #include <boost/accumulators/framework/depends_on.hpp> // for feature_tag 14 #include <boost/accumulators/framework/accumulator_base.hpp> 15 #include <boost/accumulators/framework/extractor.hpp> 16 17 namespace boost { namespace accumulators 18 { 19 20 namespace impl 21 { 22 23 ////////////////////////////////////////////////////////////////////////// 24 // value_accumulator_impl 25 template<typename ValueType, typename Tag> 26 struct value_accumulator_impl 27 : accumulator_base 28 { 29 typedef ValueType result_type; 30 31 template<typename Args> value_accumulator_implboost::accumulators::impl::value_accumulator_impl32 value_accumulator_impl(Args const &args) 33 : val(args[parameter::keyword<Tag>::get()]) 34 { 35 } 36 resultboost::accumulators::impl::value_accumulator_impl37 result_type result(dont_care) const 38 { 39 return this->val; 40 } 41 42 private: 43 ValueType val; 44 }; 45 46 } // namespace impl 47 48 namespace tag 49 { 50 ////////////////////////////////////////////////////////////////////////// 51 // value_tag 52 template<typename Tag> 53 struct value_tag 54 { 55 }; 56 57 ////////////////////////////////////////////////////////////////////////// 58 // value 59 template<typename ValueType, typename Tag> 60 struct value 61 : depends_on<> 62 { 63 /// INTERNAL ONLY 64 /// 65 typedef mpl::always<accumulators::impl::value_accumulator_impl<ValueType, Tag> > impl; 66 }; 67 } 68 69 namespace extract 70 { 71 BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, value, (typename)(typename)) 72 BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, value_tag, (typename)) 73 } 74 75 using extract::value; 76 using extract::value_tag; 77 78 // Map all value<V,T> features to value_tag<T> so 79 // that values can be extracted using value_tag<T> 80 // without specifying the value type. 81 template<typename ValueType, typename Tag> 82 struct feature_of<tag::value<ValueType, Tag> > 83 : feature_of<tag::value_tag<Tag> > 84 { 85 }; 86 87 }} // namespace boost::accumulators 88 89 #endif 90