// Boost.Units - A C++ library for zero-overhead dimensional analysis and // unit/quantity manipulation and conversion // // Copyright (C) 2003-2008 Matthias Christian Schabel // Copyright (C) 2007-2008 Steven Watanabe // // 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) /// \file /// \brief base dimensions (mass, length, time...). /// \details base dimension definition registration. #ifndef BOOST_UNITS_BASE_DIMENSION_HPP #define BOOST_UNITS_BASE_DIMENSION_HPP #include <boost/units/config.hpp> #include <boost/units/dim.hpp> #include <boost/units/static_rational.hpp> #include <boost/units/units_fwd.hpp> #include <boost/units/detail/dimension_list.hpp> #include <boost/units/detail/ordinal.hpp> #include <boost/units/detail/prevent_redefinition.hpp> namespace boost { namespace units { /// This must be in namespace boost::units so that ADL /// will work with friend functions defined inline. /// INTERNAL ONLY template<long N> struct base_dimension_ordinal { }; /// INTERNAL ONLY template<class T, long N> struct base_dimension_pair { }; /// INTERNAL ONLY template<class T, long N> struct check_base_dimension { enum { value = sizeof(boost_units_is_registered(units::base_dimension_ordinal<N>())) == sizeof(detail::yes) && sizeof(boost_units_is_registered(units::base_dimension_pair<T, N>())) != sizeof(detail::yes) }; }; /// Defines a base dimension. To define a dimension you need to provide /// the derived class (CRTP) and a unique integer. /// @code /// struct my_dimension : boost::units::base_dimension<my_dimension, 1> {}; /// @endcode /// It is designed so that you will get an error message if you try /// to use the same value in multiple definitions. template<class Derived, long N #if !defined(BOOST_UNITS_DOXYGEN) && !defined(__BORLANDC__) , class = typename detail::ordinal_has_already_been_defined< check_base_dimension<Derived, N>::value >::type #endif > class base_dimension : public ordinal<N> { public: /// INTERNAL ONLY typedef base_dimension this_type; /// A convenience typedef. Equivalent to boost::units::derived_dimension<Derived,1>::type. #ifndef BOOST_UNITS_DOXYGEN typedef list<dim<Derived,static_rational<1> >, dimensionless_type> dimension_type; #else typedef detail::unspecified dimension_type; #endif /// Provided for mpl compatability. typedef Derived type; private: /// Check for C++0x. In C++0x, we have to have identical /// arguments but a different return type to trigger an /// error. Note that this is only needed for clang as /// check_base_dimension will trigger an error earlier /// for compilers with less strict name lookup. /// INTERNAL ONLY friend Derived* check_double_register(const units::base_dimension_ordinal<N>&) { return(0); } /// Register this ordinal /// INTERNAL ONLY friend detail::yes boost_units_is_registered(const units::base_dimension_ordinal<N>&) { detail::yes result; return(result); } /// But make sure we can identify the current instantiation! /// INTERNAL ONLY friend detail::yes boost_units_is_registered(const units::base_dimension_pair<Derived, N>&) { detail::yes result; return(result); } }; } // namespace units } // namespace boost #endif // BOOST_UNITS_BASE_DIMENSION_HPP