Full merge from trunk at revision 41356 of entire boost-root tree.

[SVN r41370]

example/detail/param_type.hpp

@@ -0,0 +1,71 @@
+
+// (C) Copyright Tobias Schwinger
+//
+// Use modification and distribution are subject to the boost Software License,
+// Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt).
+
+//------------------------------------------------------------------------------
+
+// Metafunction to compute optimal parameter type for argument forwarding. 
+
+// This header is not an FT example in itself -- it's used by some of them to 
+// optimize argument forwarding. 
+//
+// For more details see 'fast_mem_fn.hpp' in this directory or the documentation
+// of the CallTraits utility [1].
+//
+//
+// References
+// ==========
+//
+// [1] http://www.boost.org/libs/utility/call_traits.htm
+
+#ifndef BOOST_UTILITY_PARAM_TYPE_HPP_INCLUDED
+#define BOOST_UTILITY_PARAM_TYPE_HPP_INCLUDED
+
+#include <boost/config.hpp>
+
+#include <boost/type_traits/add_const.hpp>
+#include <boost/type_traits/add_reference.hpp>
+
+#include <boost/mpl/eval_if.hpp>
+#include <boost/mpl/identity.hpp>
+
+#include <boost/mpl/aux_/lambda_support.hpp>
+// #include <boost/type_traits/detail/template_arity_spec.hpp>
+
+// namespace boost
+namespace example
+{
+  namespace mpl = boost::mpl;
+
+  // namespace utility
+  // {
+    namespace param_type_detail
+    {
+      template<typename T>
+      struct by_ref_cond
+      {
+        typedef by_ref_cond type;
+        BOOST_STATIC_CONSTANT(bool,value = sizeof(void*) < sizeof(T));
+      };
+
+      template<typename T>
+      struct add_ref_to_const
+        : boost::add_reference< typename boost::add_const<T>::type >
+      { };
+    }
+
+    template<typename T>
+    struct param_type
+      : mpl::eval_if< param_type_detail::by_ref_cond<T> 
+                    , param_type_detail::add_ref_to_const<T>, mpl::identity<T> >
+    { 
+      BOOST_MPL_AUX_LAMBDA_SUPPORT(1,param_type,(T))
+    };
+  // }
+  // BOOST_TT_AUX_TEMPLATE_ARITY_SPEC(1,utility::param_type)
+}
+
+#endif
+