function_base.hpp:

- Add trivial_manager that does nothing but copy object pointers
  - Add is_ref to determine if a type is a reference_wrapper
  - Add function_obj_ref_tag for reference_wrappers
  - Teach get_function_tag about reference_wrappers

function_template.hpp:
  - Add assign_to overload for reference_wrappers (these don't throw)


[SVN r11875]

include/boost/function/function_base.hpp

@@ -23,6 +23,7 @@
 #include <typeinfo>
 #include <boost/config.hpp>
 #include <boost/type_traits.hpp>
+#include <boost/ref.hpp>
 
 namespace boost {
   namespace detail {
@@ -70,6 +71,37 @@ namespace boost {
         typedef typename select::template Result<Then,Else>::type type;
       };
 
+      // Determine if the incoming argument is a reference_wrapper
+#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
+      template<typename T>
+      struct is_ref
+      {
+	BOOST_STATIC_CONSTANT(bool, value = false); 
+      };
+
+      template<typename T>
+      struct is_ref<reference_wrapper<T> >
+      {
+	BOOST_STATIC_CONSTANT(bool, value = true);
+      };
+#else // no partial specialization
+      typedef char yes_type;
+      typedef double no_type;
+      
+      no_type is_ref_tester(...);
+
+      template<typename T>
+      yes_type is_ref_tester(reference_wrapper<T>*);
+
+      template<typename T>
+      struct is_ref
+      {
+	static T* t;
+	BOOST_STATIC_CONSTANT(bool, 
+	  value = (sizeof(is_ref_tester(t)) == sizeof(yes_type)));
+      };
+#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
+
       /**
        * A union of a function pointer and a void pointer. This is necessary
        * because 5.2.10/6 allows reinterpret_cast<> to safely cast between 
@@ -122,6 +154,7 @@ namespace boost {
       struct function_ptr_tag {};
       struct function_obj_tag {};
       struct member_ptr_tag {};
+      struct function_obj_ref_tag {};
 
       template<typename F>
       class get_function_tag
@@ -130,12 +163,26 @@ namespace boost {
                             function_ptr_tag,
                             function_obj_tag>::type ptr_or_obj_tag;
 
-      public:
 	typedef typename IF<(is_member_pointer<F>::value),
 			    member_ptr_tag,
-			    ptr_or_obj_tag>::type type;
+			    ptr_or_obj_tag>::type ptr_or_obj_or_mem_tag;
+      public:
+	typedef typename IF<(is_ref<F>::value),
+			     function_obj_ref_tag,
+			     ptr_or_obj_or_mem_tag>::type type;
       };
 
+      // The trivial manager does nothing but return the same pointer (if we
+      // are cloning) or return the null pointer (if we are deleting).
+      any_pointer trivial_manager(any_pointer f, 
+				  functor_manager_operation_type op)
+      {
+	if (op == clone_functor_tag)
+	  return f;
+	else
+	  return any_pointer(reinterpret_cast<void*>(0));
+      }
+
       /**
        * The functor_manager class contains a static function "manage" which
        * can clone or destroy the given function/function object pointer. 

include/boost/function/function_template.hpp

@@ -391,6 +391,28 @@ namespace boost {
       }
     }
     
+    template<typename FunctionObj>
+    void assign_to(const reference_wrapper<FunctionObj>& f, 
+		   detail::function::function_obj_ref_tag)
+    {
+      if (!detail::function::has_empty_target(&f.get())) {
+        typedef 
+          typename detail::function::BOOST_FUNCTION_GET_FUNCTION_OBJ_INVOKER<
+                                       FunctionObj,
+                                       R BOOST_FUNCTION_COMMA
+                                       BOOST_FUNCTION_TEMPLATE_ARGS
+                                     >::type
+          invoker_type;
+    
+        invoker = &invoker_type::invoke;
+        manager = &detail::function::trivial_manager;
+        functor = 
+          manager(detail::function::any_pointer(
+		    const_cast<FunctionObj*>(&f.get())),
+                  detail::function::clone_functor_tag);
+      }
+    }
+    
     typedef result_type (*invoker_type)(detail::function::any_pointer
                                         BOOST_FUNCTION_COMMA
                                         BOOST_FUNCTION_TEMPLATE_ARGS);