units/detail/dimensionless_unit.hpp

0001 // Boost.Units - A C++ library for zero-overhead dimensional analysis and
0002 // unit/quantity manipulation and conversion
0003 //
0004 // Copyright (C) 2003-2008 Matthias Christian Schabel
0005 // Copyright (C) 2007-2008 Steven Watanabe
0006 //
0007 // Distributed under the Boost Software License, Version 1.0. (See
0008 // accompanying file LICENSE_1_0.txt or copy at
0009 // http://www.boost.org/LICENSE_1_0.txt)
0010
0011 #ifndef BOOST_UNITS_DETAIL_DIMENSIONLESS_UNIT_HPP
0012 #define BOOST_UNITS_DETAIL_DIMENSIONLESS_UNIT_HPP
0013
0014 #include <boost/mpl/bool.hpp>
0015 #include <boost/units/units_fwd.hpp>
0016
0017 namespace boost {
0018 namespace units {
0019
0020 template<class T>
0021 struct heterogeneous_system;
0022
0023 template<class T>
0024 struct homogeneous_system;
0025
0026 template<class T1, class T2, class Scale>
0027 struct heterogeneous_system_impl;
0028
0029 typedef boost::units::heterogeneous_system<
0030     boost::units::heterogeneous_system_impl<
0031         boost::units::dimensionless_type,
0032         boost::units::dimensionless_type,
0033         boost::units::dimensionless_type
0034     >
0035 > heterogeneous_dimensionless_system;
0036
0037 namespace detail {
0038
0039 template<class System>
0040 struct void_if_dimensionless {
0041     typedef int type;
0042 };
0043
0044 template<class T>
0045 struct void_if_dimensionless<boost::units::homogeneous_system<T> > {
0046     typedef void type;
0047 };
0048
0049 template<>
0050 struct void_if_dimensionless<heterogeneous_dimensionless_system> {
0051     typedef void type;
0052 };
0053
0054 template<class System, class Test = void>
0055 struct void_if_heterogeneous {
0056     typedef void type;
0057 };
0058
0059 template<class System>
0060 struct void_if_heterogeneous<System, typename void_if_dimensionless<System>::type> {
0061     typedef int type;
0062 };
0063
0064 template<class System, class Enable=void>
0065 struct is_dimensionless_system : mpl::false_ {};
0066
0067 template<class System>
0068 struct is_dimensionless_system<System, typename void_if_dimensionless<System>::type> : mpl::true_ {};
0069
0070 #define BOOST_UNITS_DIMENSIONLESS_UNIT(T)\
0071     boost::units::unit<\
0072         boost::units::dimensionless_type,\
0073         T,\
0074         typename ::boost::units::detail::void_if_dimensionless<T>::type\
0075     >
0076
0077 #define BOOST_UNITS_HETEROGENEOUS_DIMENSIONLESS_UNIT(T)\
0078     boost::units::unit<\
0079         boost::units::dimensionless_type,\
0080         T,\
0081         typename ::boost::units::detail::void_if_heterogeneous<T>::type\
0082     >
0083
0084 }
0085 }
0086 }
0087
0088 #endif