168 lines
5.5 KiB
C++
168 lines
5.5 KiB
C++
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// (C) Copyright Jeremy Siek 2004
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// Distributed under 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 BOOST_PROPERTY_HPP
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#define BOOST_PROPERTY_HPP
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#include <boost/mpl/bool.hpp>
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namespace boost {
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struct no_property {
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typedef no_property tag_type;
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typedef no_property next_type;
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typedef no_property value_type;
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enum { num = 0 };
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typedef void kind;
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};
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template <class Tag, class T, class Base = no_property>
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struct property : public Base {
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typedef Base next_type;
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typedef Tag tag_type;
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typedef T value_type;
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#if BOOST_WORKAROUND (__GNUC__, < 3)
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property() { }
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#else
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property() : m_value() { }
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#endif
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property(const T& v) : m_value(v) { }
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property(const T& v, const Base& b) : Base(b), m_value(v) { }
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// copy constructor and assignment operator will be generated by compiler
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T m_value;
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};
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// The BGL properties specialize property_kind and
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// property_num, and use enum's for the Property type (see
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// graph/properties.hpp), but the user may want to use a class
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// instead with a nested kind type and num. Also, we may want to
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// switch BGL back to using class types for properties at some point.
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template <class PropertyTag>
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struct property_kind {
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typedef typename PropertyTag::kind type;
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};
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template <class P>
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struct has_property : boost::mpl::true_ {};
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template <>
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struct has_property<no_property> : boost::mpl::false_ {};
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} // namespace boost
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#include <boost/pending/detail/property.hpp>
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namespace boost {
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template <class PropertyList, class Tag>
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struct property_value {
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#if !defined BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
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typedef typename detail::build_property_tag_value_alist<PropertyList>::type AList;
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typedef typename detail::extract_value<AList,Tag>::type type;
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#else
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typedef typename detail::build_property_tag_value_alist<PropertyList>::type AList;
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typedef typename detail::ev_selector<AList>::type Extractor;
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typedef typename Extractor::template bind_<AList,Tag>::type type;
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#endif
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};
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template <class Tag2>
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inline detail::error_property_not_found
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get_property_value(const no_property&, Tag2) {
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return detail::error_property_not_found();
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}
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template <class Tag1, class Tag2, class T1, class Base>
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inline typename property_value<property<Tag1,T1,Base>, Tag2>::type&
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get_property_value(property<Tag1,T1,Base>& p, Tag2 tag2) {
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BOOST_STATIC_CONSTANT(bool,
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match = (detail::same_property<Tag1,Tag2>::value));
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typedef property<Tag1,T1,Base> Prop;
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typedef typename property_value<Prop, Tag2>::type T2;
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T2* t2 = 0;
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typedef detail::property_value_dispatch<match> Dispatcher;
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return Dispatcher::get_value(p, t2, tag2);
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}
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template <class Tag1, class Tag2, class T1, class Base>
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inline
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const typename property_value<property<Tag1,T1,Base>, Tag2>::type&
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get_property_value(const property<Tag1,T1,Base>& p, Tag2 tag2) {
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BOOST_STATIC_CONSTANT(bool,
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match = (detail::same_property<Tag1,Tag2>::value));
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typedef property<Tag1,T1,Base> Prop;
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typedef typename property_value<Prop, Tag2>::type T2;
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T2* t2 = 0;
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typedef detail::property_value_dispatch<match> Dispatcher;
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return Dispatcher::const_get_value(p, t2, tag2);
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}
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namespace detail {
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/** This trait returns true if T is no_property. */
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template <typename T>
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struct is_no_property
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: mpl::bool_<is_same<T, no_property>::value>
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{ };
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#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
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/** @internal @name Retag Property List
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* This metafunction is used internally to normalize a property if it is
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* actually modeling a property. Specifically this is used in Boost.Graph
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* to map user-provided classes into bundled properties.
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*/
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//@{
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// One base case of the recursive form (see below). This matches any
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// retag request that does not include a property<...> or no_property as
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// the FinalType. This is used for generating bundles in Boost.Graph.
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template<typename FinalTag, typename FinalType>
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struct retag_property_list
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{
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typedef property<FinalTag, FinalType> type;
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typedef FinalType retagged;
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};
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// Recursively retag the nested property list.
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template<typename FinalTag, typename Tag, typename T, typename Base>
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struct retag_property_list<FinalTag, property<Tag, T, Base> >
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{
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private:
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typedef retag_property_list<FinalTag, Base> next;
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public:
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typedef property<Tag, T, typename next::type> type;
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typedef typename next::retagged retagged;
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};
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// This base case will correctly deduce the final property type if the
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// retagged property is given in property form. This should not hide
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// the base case below.
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// NOTE: This addresses a problem of layering bundled properties in the BGL
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// where multiple retaggings will fail to deduce the correct retagged
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// type.
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template<typename FinalTag, typename FinalType>
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struct retag_property_list<FinalTag, property<FinalTag, FinalType> >
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{
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public:
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typedef property<FinalTag, FinalType> type;
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typedef FinalType retagged;
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};
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// A final base case of the retag_property_list, this will terminate a
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// properly structured list.
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template<typename FinalTag>
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struct retag_property_list<FinalTag, no_property>
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{
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typedef no_property type;
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typedef no_property retagged;
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};
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//@}
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#endif
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} // namespace detail
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} // namesapce boost
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#endif /* BOOST_PROPERTY_HPP */
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