[Boost-commit] svn:boost r52902 - trunk/boost/pending

Subject: [Boost-commit] svn:boost r52902 - trunk/boost/pending
From: asutton_at_[hidden]
Date: 2009-05-11 08:58:38

Author: asutton
Date: 2009-05-11 08:58:37 EDT (Mon, 11 May 2009)
New Revision: 52902
URL: http://svn.boost.org/trac/boost/changeset/52902

Log:
Added a specialization of retag_property_list that will correctly retag
bundled properties given in "property form".

Text files modified: 
   trunk/boost/pending/property.hpp |   100 +++++++++++++++++++++++++-------------- 
   1 files changed, 64 insertions(+), 36 deletions(-)

Modified: trunk/boost/pending/property.hpp
==============================================================================
--- trunk/boost/pending/property.hpp	(original)
+++ trunk/boost/pending/property.hpp	2009-05-11 08:58:37 EDT (Mon, 11 May 2009)
@@ -1,4 +1,4 @@
-//  (C) Copyright Jeremy Siek 2004 
+//  (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)
@@ -10,7 +10,7 @@
 
 namespace boost {
 
-  struct no_property { 
+  struct no_property {
     typedef no_property tag_type;
     typedef no_property next_type;
     typedef no_property value_type;
@@ -47,14 +47,14 @@
   };
 
   template <class P>
-  struct has_property { 
+  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; 
+  struct has_property<no_property> {
+    BOOST_STATIC_CONSTANT(bool, value = false);
+    typedef false_type type;
   };
 
 } // namespace boost
@@ -72,7 +72,7 @@
     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  
+#endif
   };
 
   template <class Tag2>
@@ -82,9 +82,9 @@
   }
 
   template <class Tag1, class Tag2, class T1, class Base>
-  inline typename property_value<property<Tag1,T1,Base>, Tag2>::type& 
+  inline typename property_value<property<Tag1,T1,Base>, Tag2>::type&
   get_property_value(property<Tag1,T1,Base>& p, Tag2 tag2) {
-    BOOST_STATIC_CONSTANT(bool, 
+    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;
@@ -94,9 +94,9 @@
   }
   template <class Tag1, class Tag2, class T1, class Base>
   inline
-  const typename property_value<property<Tag1,T1,Base>, Tag2>::type& 
+  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, 
+    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;
@@ -107,32 +107,60 @@
 
  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;
-   };
+    /** @internal @name Retag Property List
+     * This metafunction is used internally to normalize a property if it is
+     * actually modeling a property. Specifically this is used in Boost.Graph
+     * to map user-provided classes into bundled properties.
+     */
+    //@{
+    // One base case of the recursive form (see below). This matches any
+    // retag request that does not include a property<...> or no_property as
+    // the FinalType. This is used for generating bundles in Boost.Graph.
+    template<typename FinalTag, typename FinalType>
+    struct retag_property_list
+    {
+        typedef property<FinalTag, FinalType> type;
+        typedef FinalType retagged;
+    };
+
+    // Recursively retag the nested property list.
+    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;
+    };
+
+    // This base case will correctly deduce the final property type if the
+    // retagged property is given in property form. This should not hide
+    // the base case below.
+    // NOTE: This addresses a problem of layering bundled properties in the BGL
+    // where multiple retaggings will fail to deduce the correct retagged
+    // type.
+    template<typename FinalTag, typename FinalType>
+    struct retag_property_list<FinalTag, property<FinalTag, FinalType> >
+    {
+    public:
+        typedef property<FinalTag, FinalType> type;
+        typedef FinalType retagged;
+    };
+
+    // A final base case of the retag_propert_list, this will terminate a
+    // properly structured list.
+    template<typename FinalTag>
+    struct retag_property_list<FinalTag, no_property>
+    {
+        typedef no_property type;
+        typedef no_property retagged;
+    };
+    //@}
 #endif
-  }
+} // namespace detail
+
 } // namesapce boost
 
 #endif /* BOOST_PROPERTY_HPP */