ceph/src/boost/boost/units/detail/dim_impl.hpp

   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