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152 lines
5.2 KiB
152 lines
5.2 KiB
// Copyright Daniel Wallin, David Abrahams 2005. Use, modification and |
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// distribution is subject to the Boost Software License, Version 1.0. (See |
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// accompanying file LICENSE_1_0.txt or copy at |
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// http://www.boost.org/LICENSE_1_0.txt) |
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#ifndef KEYWORD_050328_HPP |
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#define KEYWORD_050328_HPP |
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#include <boost/parameter/aux_/unwrap_cv_reference.hpp> |
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#include <boost/parameter/aux_/tag.hpp> |
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#include <boost/parameter/aux_/default.hpp> |
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namespace boost { namespace parameter { |
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// Instances of unique specializations of keyword<...> serve to |
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// associate arguments with parameter names. For example: |
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// |
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// struct rate_; // parameter names |
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// struct skew_; |
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// namespace |
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// { |
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// keyword<rate_> rate; // keywords |
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// keyword<skew_> skew; |
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// } |
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// |
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// ... |
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// |
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// f(rate = 1, skew = 2.4); |
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// |
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template <class Tag> |
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struct keyword |
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{ |
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template <class T> |
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typename aux::tag<Tag, T>::type const |
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operator=(T& x) const |
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{ |
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typedef typename aux::tag<Tag, T>::type result; |
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return result(x); |
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} |
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template <class Default> |
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aux::default_<Tag, Default> |
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operator|(Default& default_) const |
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{ |
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return aux::default_<Tag, Default>(default_); |
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} |
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template <class Default> |
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aux::lazy_default<Tag, Default> |
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operator||(Default& default_) const |
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{ |
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return aux::lazy_default<Tag, Default>(default_); |
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} |
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#if !BOOST_WORKAROUND(BOOST_MSVC, < 1300) // avoid partial ordering bugs |
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template <class T> |
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typename aux::tag<Tag, T const>::type const |
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operator=(T const& x) const |
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{ |
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typedef typename aux::tag<Tag, T const>::type result; |
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return result(x); |
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} |
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#endif |
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#if !BOOST_WORKAROUND(BOOST_MSVC, < 1300) // avoid partial ordering bugs |
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template <class Default> |
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aux::default_<Tag, const Default> |
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operator|(const Default& default_) const |
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#if BOOST_WORKAROUND(BOOST_MSVC, == 1300) |
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volatile |
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#endif |
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{ |
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return aux::default_<Tag, const Default>(default_); |
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} |
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template <class Default> |
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aux::lazy_default<Tag, Default> |
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operator||(Default const& default_) const |
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#if BOOST_WORKAROUND(BOOST_MSVC, == 1300) |
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volatile |
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#endif |
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{ |
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return aux::lazy_default<Tag, Default>(default_); |
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} |
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#endif |
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public: // Insurance against ODR violations |
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// People will need to define these keywords in header files. To |
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// prevent ODR violations, it's important that the keyword used in |
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// every instantiation of a function template is the same object. |
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// We provide a reference to a common instance of each keyword |
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// object and prevent construction by users. |
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static keyword<Tag> const instance; |
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// This interface is deprecated |
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static keyword<Tag>& get() |
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{ |
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return const_cast<keyword<Tag>&>(instance); |
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} |
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}; |
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template <class Tag> |
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keyword<Tag> const keyword<Tag>::instance = {}; |
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// Reduces boilerplate required to declare and initialize keywords |
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// without violating ODR. Declares a keyword tag type with the given |
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// name in namespace tag_namespace, and declares and initializes a |
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// reference in an anonymous namespace to a singleton instance of that |
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// type. |
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#if BOOST_WORKAROUND(BOOST_MSVC, < 1300) |
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# define BOOST_PARAMETER_KEYWORD(tag_namespace,name) \ |
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namespace tag_namespace \ |
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{ \ |
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struct name \ |
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{ \ |
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static char const* keyword_name() \ |
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{ \ |
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return #name; \ |
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} \ |
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}; \ |
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} \ |
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static ::boost::parameter::keyword<tag_namespace::name> const& name \ |
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= ::boost::parameter::keyword<tag_namespace::name>::instance; |
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#else |
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#define BOOST_PARAMETER_KEYWORD(tag_namespace,name) \ |
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namespace tag_namespace \ |
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{ \ |
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struct name \ |
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{ \ |
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static char const* keyword_name() \ |
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{ \ |
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return #name; \ |
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} \ |
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}; \ |
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} \ |
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namespace \ |
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{ \ |
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::boost::parameter::keyword<tag_namespace::name> const& name \ |
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= ::boost::parameter::keyword<tag_namespace::name>::instance;\ |
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} |
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#endif |
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}} // namespace boost::parameter |
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#endif // KEYWORD_050328_HPP |
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