1 // Boost.Units - A C++ library for zero-overhead dimensional analysis and 2 // unit/quantity manipulation and conversion 3 // 4 // Copyright (C) 2003-2008 Matthias Christian Schabel 5 // Copyright (C) 2008 Steven Watanabe 6 // 7 // Distributed under the Boost Software License, Version 1.0. (See 8 // accompanying file LICENSE_1_0.txt or copy at 9 // http://www.boost.org/LICENSE_1_0.txt) 10 11 #ifndef BOOST_UNITS_DIM_IMPL_HPP 12 #define BOOST_UNITS_DIM_IMPL_HPP 13 14 #include <boost/mpl/bool.hpp> 15 #include <boost/mpl/less.hpp> 16 17 #include <boost/units/units_fwd.hpp> 18 19 /// \file 20 /// \brief Class encapsulating a dimension tag/value pair 21 22 namespace boost { 23 24 namespace units { 25 26 namespace detail { 27 28 struct dim_tag; 29 30 } 31 32 } 33 34 namespace mpl { 35 36 /// Less than comparison for sorting @c dim. 37 template<> 38 struct less_impl<boost::units::detail::dim_tag, boost::units::detail::dim_tag> 39 { 40 template<class T0, class T1> 41 struct apply : mpl::less<typename T0::tag_type, typename T1::tag_type> {}; 42 }; 43 44 } 45 46 namespace units { 47 48 template<class Tag, class Exponent> 49 struct dim; 50 51 template<long N, long D> 52 class static_rational; 53 54 namespace detail { 55 56 /// Extract @c tag_type from a @c dim. 57 template<typename T> 58 struct get_tag 59 { 60 typedef typename T::tag_type type; 61 }; 62 63 /// Extract @c value_type from a @c dim. 64 template<typename T> 65 struct get_value 66 { 67 typedef typename T::value_type type; 68 }; 69 70 /// Determine if a @c dim is empty (has a zero exponent). 71 template<class T> 72 struct is_empty_dim; 73 74 template<typename T> 75 struct is_empty_dim< dim<T, static_rational<0, 1> > > : 76 mpl::true_ 77 { }; 78 79 template<typename T, typename V> 80 struct is_empty_dim< dim<T, V> > : 81 mpl::false_ 82 { }; 83 84 } // namespace detail 85 86 } // namespace units 87 88 } // namespace boost 89 90 #endif // BOOST_UNITS_DIM_IMPL_HPP 91