reduce number of template instantiations

[SVN r53566]

include/boost/fusion/support/detail/access.hpp

@@ -7,12 +7,8 @@
 #if !defined(FUSION_ACCESS_04182005_0737)
 #define FUSION_ACCESS_04182005_0737
 
-#include <boost/mpl/eval_if.hpp>
-#include <boost/mpl/identity.hpp>
 #include <boost/type_traits/add_const.hpp>
 #include <boost/type_traits/add_reference.hpp>
-#include <boost/type_traits/is_reference.hpp>
-#include <boost/type_traits/remove_cv.hpp>
 
 namespace boost { namespace fusion { namespace detail
 {
@@ -33,22 +29,35 @@ namespace boost { namespace fusion { namespace detail
     };
 
     template <typename T>
-    struct non_ref_parameter
+    struct call_param
     {
-        typedef typename boost::remove_cv<T>::type const& type;
+        typedef T const& type;
     };
 
     template <typename T>
-    struct call_param
+    struct call_param<T &>
     {
-        typedef typename 
-            mpl::eval_if<
-                is_reference<T>
-              , mpl::identity<T>
-              , non_ref_parameter<T>
-            >::type
-        type;
+        typedef T& type;
     };
+
+    template <typename T>
+    struct call_param<T const>
+    {
+        typedef T const& type;
+    };
+
+    template <typename T>
+    struct call_param<T volatile>
+    {
+        typedef T const& type;
+    };
+
+    template <typename T>
+    struct call_param<T const volatile>
+    {
+        typedef T const& type;
+    };
+
 }}}
 
 #endif