boost/units/detail/prevent_redefinition.hpp
// 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) #ifndef BOOST_UNITS_DETAIL_PREVENT_REDEFINITION_HPP #define BOOST_UNITS_DETAIL_PREVENT_REDEFINITION_HPP #include <boost/mpl/long.hpp> namespace boost { namespace units { namespace detail { struct no { no() {} char dummy; }; struct yes { no dummy[2]; }; template<bool> struct ordinal_has_already_been_defined; template<> struct ordinal_has_already_been_defined<true> { }; template<> struct ordinal_has_already_been_defined<false> { typedef void type; }; } /// This must be in namespace boost::units so that ADL /// will work. we need a mangled name because it must /// be found by ADL /// INTERNAL ONLY template<class T> detail::no boost_units_is_registered(const T&) { detail::no result; return(result); } /// INTERNAL ONLY template<class T> detail::no boost_units_unit_is_registered(const T&) { detail::no result; return(result); } } // namespace units } // namespace boost #endif // BOOST_UNITS_PREVENT_ORDINAL_REDEFINITION_IMPL_HPP