Chris@16: // Boost.Units - A C++ library for zero-overhead dimensional analysis and 
Chris@16: // unit/quantity manipulation and conversion
Chris@16: //
Chris@16: // Copyright (C) 2003-2008 Matthias Christian Schabel
Chris@16: // Copyright (C) 2007-2008 Steven Watanabe
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: /// \file
Chris@16: /// \brief base unit (meter, kg, sec...).
Chris@16: /// \details base unit definition registration.
Chris@16: 
Chris@16: #ifndef BOOST_UNITS_BASE_UNIT_HPP
Chris@16: #define BOOST_UNITS_BASE_UNIT_HPP
Chris@16: 
Chris@16: #include <boost/units/config.hpp>
Chris@16: #include <boost/units/heterogeneous_system.hpp>
Chris@16: #include <boost/units/static_rational.hpp>
Chris@16: #include <boost/units/units_fwd.hpp>
Chris@16: #include <boost/units/unit.hpp>
Chris@16: #include <boost/units/detail/dimension_list.hpp>
Chris@16: #include <boost/units/detail/ordinal.hpp>
Chris@16: #include <boost/units/detail/prevent_redefinition.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@16: 
Chris@16: namespace units {
Chris@16: 
Chris@16: /// This must be in namespace boost::units so that ADL
Chris@16: /// will work with friend functions defined inline.
Chris@16: /// Base dimensions and base units are independent.
Chris@16: /// INTERNAL ONLY
Chris@16: template<long N> struct base_unit_ordinal { };
Chris@16: 
Chris@16: /// INTERNAL ONLY
Chris@16: template<class T, long N> struct base_unit_pair { };
Chris@16: 
Chris@16: /// INTERNAL ONLY
Chris@16: template<class T, long N>
Chris@16: struct check_base_unit {
Chris@16:     enum {
Chris@16:         value =
Chris@16:             sizeof(boost_units_unit_is_registered(units::base_unit_ordinal<N>())) == sizeof(detail::yes) &&
Chris@16:             sizeof(boost_units_unit_is_registered(units::base_unit_pair<T, N>())) != sizeof(detail::yes)
Chris@16:     };
Chris@16: };
Chris@16: 
Chris@16: /// Defines a base unit.  To define a unit you need to provide
Chris@16: /// the derived class (CRTP), a dimension list and a unique integer.
Chris@16: /// @code
Chris@16: /// struct my_unit : boost::units::base_unit<my_unit, length_dimension, 1> {};
Chris@16: /// @endcode
Chris@16: /// It is designed so that you will get an error message if you try
Chris@16: /// to use the same value in multiple definitions.
Chris@16: template<class Derived,
Chris@16:          class Dim,
Chris@16:          long N
Chris@16: #if !defined(BOOST_UNITS_DOXYGEN) && !defined(__BORLANDC__)
Chris@16:          ,
Chris@16:          class = typename detail::ordinal_has_already_been_defined<
Chris@16:              check_base_unit<Derived, N>::value
Chris@16:          >::type
Chris@16: #endif
Chris@16: >
Chris@16: class base_unit : 
Chris@16:     public ordinal<N> 
Chris@16: {
Chris@16:     public:
Chris@16:         /// INTERNAL ONLY
Chris@16:         typedef void boost_units_is_base_unit_type;
Chris@16:         /// INTERNAL ONLY
Chris@16:         typedef base_unit           this_type;
Chris@16:         /// The dimensions of this base unit.
Chris@16:         typedef Dim                 dimension_type;
Chris@16: 
Chris@16:         /// Provided for mpl compatability.
Chris@16:         typedef Derived type;
Chris@16: 
Chris@16:         /// The unit corresponding to this base unit.
Chris@16: #ifndef BOOST_UNITS_DOXYGEN
Chris@16:         typedef unit<
Chris@16:             Dim,
Chris@16:             heterogeneous_system<
Chris@16:                 heterogeneous_system_impl<
Chris@16:                     list<
Chris@16:                         heterogeneous_system_dim<Derived,static_rational<1> >,
Chris@16:                         dimensionless_type
Chris@16:                     >,
Chris@16:                     Dim,
Chris@16:                     no_scale
Chris@16:                 >
Chris@16:             >
Chris@16:         > unit_type;
Chris@16: #else
Chris@16:         typedef detail::unspecified unit_type;
Chris@16: #endif
Chris@16: 
Chris@16:     private:
Chris@16:         /// Check for C++0x.  In C++0x, we have to have identical
Chris@16:         /// arguments but a different return type to trigger an
Chris@16:         /// error.  Note that this is only needed for clang as
Chris@16:         /// check_base_unit will trigger an error earlier
Chris@16:         /// for compilers with less strict name lookup.
Chris@16:         /// INTERNAL ONLY
Chris@16:         friend Derived* 
Chris@16:         check_double_register(const units::base_unit_ordinal<N>&) 
Chris@16:         { return(0); }
Chris@16: 
Chris@16:         /// Register this ordinal
Chris@16:         /// INTERNAL ONLY
Chris@16:         friend detail::yes 
Chris@16:         boost_units_unit_is_registered(const units::base_unit_ordinal<N>&) 
Chris@16:         { detail::yes result; return(result); }
Chris@16:         
Chris@16:         /// But make sure we can identify the current instantiation!
Chris@16:         /// INTERNAL ONLY
Chris@16:         friend detail::yes 
Chris@16:         boost_units_unit_is_registered(const units::base_unit_pair<Derived, N>&) 
Chris@16:         { detail::yes result; return(result); }
Chris@16: };
Chris@16: 
Chris@16: } // namespace units
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif // BOOST_UNITS_BASE_UNIT_HPP