//  (C) Copyright Jeremy Siek 2004 

 //  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_PROPERTY_HPP

 #define BOOST_PROPERTY_HPP

 #include <boost/pending/ct_if.hpp>

 namespace boost {

   struct no_property { 

     typedef no_property tag_type;

     typedef no_property next_type;

     typedef no_property value_type;

     enum { num = 0 };

     typedef void kind;

   };

   template <class Tag, class T, class Base = no_property>

   struct property : public Base {

     typedef Base next_type;

     typedef Tag tag_type;

     typedef T value_type;

 #if BOOST_WORKAROUND (__GNUC__, < 3)

     property() { }

 #else

     property() : m_value() { }

 #endif

     property(const T& v) : m_value(v) { }

     property(const T& v, const Base& b) : Base(b), m_value(v) { }

     // copy constructor and assignment operator will be generated by compiler

     T m_value;

   };

   // The BGL properties specialize property_kind and

   // property_num, and use enum's for the Property type (see

   // graph/properties.hpp), but the user may want to use a class

   // instead with a nested kind type and num.  Also, we may want to

   // switch BGL back to using class types for properties at some point.

   template <class PropertyTag>

   struct property_kind {

     typedef typename PropertyTag::kind type;

   };

   template <class P>

   struct has_property { 

     BOOST_STATIC_CONSTANT(bool, value = true);

     typedef true_type type;

   };

   template <>

   struct has_property<no_property> { 

     BOOST_STATIC_CONSTANT(bool, value = false); 

     typedef false_type type; 

   };

 } // namespace boost

 #include <boost/pending/detail/property.hpp>

 namespace boost {

   template <class PropertyList, class Tag>

   struct property_value {

 #if !defined BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION

     typedef typename detail::build_property_tag_value_alist<PropertyList>::type AList;

     typedef typename detail::extract_value<AList,Tag>::type type;

 #else

     typedef typename detail::build_property_tag_value_alist<PropertyList>::type AList;

     typedef typename detail::ev_selector<AList>::type Extractor;

     typedef typename Extractor::template bind_<AList,Tag>::type type;

 #endif  

   };

   template <class Tag1, class Tag2, class T1, class Base>

   inline typename property_value<property<Tag1,T1,Base>, Tag2>::type& 

   get_property_value(property<Tag1,T1,Base>& p, Tag2 tag2) {

     BOOST_STATIC_CONSTANT(bool, 

                           match = (detail::same_property<Tag1,Tag2>::value));

     typedef property<Tag1,T1,Base> Prop;

     typedef typename property_value<Prop, Tag2>::type T2;

     T2* t2 = 0;

     typedef detail::property_value_dispatch<match> Dispatcher;

     return Dispatcher::get_value(p, t2, tag2);

   }

   template <class Tag1, class Tag2, class T1, class Base>

   inline

   const typename property_value<property<Tag1,T1,Base>, Tag2>::type& 

   get_property_value(const property<Tag1,T1,Base>& p, Tag2 tag2) {

     BOOST_STATIC_CONSTANT(bool, 

                           match = (detail::same_property<Tag1,Tag2>::value));

     typedef property<Tag1,T1,Base> Prop;

     typedef typename property_value<Prop, Tag2>::type T2;

     T2* t2 = 0;

     typedef detail::property_value_dispatch<match> Dispatcher;

     return Dispatcher::const_get_value(p, t2, tag2);

   }

  namespace detail {

 #if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)

    template<typename FinalTag, typename FinalType>

    struct retag_property_list

    {

      typedef property<FinalTag, FinalType> type;

      typedef FinalType retagged;

    };

    template<typename FinalTag, typename Tag, typename T, typename Base>

    struct retag_property_list<FinalTag, property<Tag, T, Base> >

    {

    private:

      typedef retag_property_list<FinalTag, Base> next;

    public:

      typedef property<Tag, T, typename next::type> type;

      typedef typename next::retagged retagged;

    };

    template<typename FinalTag>

    struct retag_property_list<FinalTag, no_property>

    {

      typedef no_property type;

      typedef no_property retagged;

    };

 #endif

   }

 } // namesapce boost

 #endif /* BOOST_PROPERTY_HPP */