// Copyright Daniel Wallin, David Abrahams 2005. Use, modification and // distribution is subject to 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 KEYWORD_050328_HPP #define KEYWORD_050328_HPP #include <boost/parameter/aux_/unwrap_cv_reference.hpp> #include <boost/parameter/aux_/tag.hpp> #include <boost/parameter/aux_/default.hpp> namespace boost { namespace parameter { // Instances of unique specializations of keyword<...> serve to // associate arguments with parameter names. For example: // // struct rate_; // parameter names // struct skew_; // namespace // { // keyword<rate_> rate; // keywords // keyword<skew_> skew; // } // // ... // // f(rate = 1, skew = 2.4); // template <class Tag> struct keyword { template <class T> typename aux::tag<Tag, T>::type const operator=(T& x) const { typedef typename aux::tag<Tag, T>::type result; return result(x); } template <class Default> aux::default_<Tag, Default> operator|(Default& default_) const { return aux::default_<Tag, Default>(default_); } template <class Default> aux::lazy_default<Tag, Default> operator||(Default& default_) const { return aux::lazy_default<Tag, Default>(default_); } #if !BOOST_WORKAROUND(BOOST_MSVC, < 1300) // avoid partial ordering bugs template <class T> typename aux::tag<Tag, T const>::type const operator=(T const& x) const { typedef typename aux::tag<Tag, T const>::type result; return result(x); } #endif #if !BOOST_WORKAROUND(BOOST_MSVC, < 1300) // avoid partial ordering bugs template <class Default> aux::default_<Tag, const Default> operator|(const Default& default_) const #if BOOST_WORKAROUND(BOOST_MSVC, == 1300) volatile #endif { return aux::default_<Tag, const Default>(default_); } template <class Default> aux::lazy_default<Tag, Default> operator||(Default const& default_) const #if BOOST_WORKAROUND(BOOST_MSVC, == 1300) volatile #endif { return aux::lazy_default<Tag, Default>(default_); } #endif public: // Insurance against ODR violations // People will need to define these keywords in header files. To // prevent ODR violations, it's important that the keyword used in // every instantiation of a function template is the same object. // We provide a reference to a common instance of each keyword // object and prevent construction by users. static keyword<Tag> const instance; // This interface is deprecated static keyword<Tag>& get() { return const_cast<keyword<Tag>&>(instance); } }; template <class Tag> keyword<Tag> const keyword<Tag>::instance = {}; // Reduces boilerplate required to declare and initialize keywords // without violating ODR. Declares a keyword tag type with the given // name in namespace tag_namespace, and declares and initializes a // reference in an anonymous namespace to a singleton instance of that // type. #if BOOST_WORKAROUND(BOOST_MSVC, < 1300) # define BOOST_PARAMETER_KEYWORD(tag_namespace,name) \ namespace tag_namespace \ { \ struct name \ { \ static char const* keyword_name() \ { \ return #name; \ } \ }; \ } \ static ::boost::parameter::keyword<tag_namespace::name> const& name \ = ::boost::parameter::keyword<tag_namespace::name>::instance; #else #define BOOST_PARAMETER_KEYWORD(tag_namespace,name) \ namespace tag_namespace \ { \ struct name \ { \ static char const* keyword_name() \ { \ return #name; \ } \ }; \ } \ namespace \ { \ ::boost::parameter::keyword<tag_namespace::name> const& name \ = ::boost::parameter::keyword<tag_namespace::name>::instance;\ } #endif }} // namespace boost::parameter #endif // KEYWORD_050328_HPP