Add SCons configure checks

[senf.git] / boost_ext / boost / parameter / aux_ / unwrap_cv_reference.hpp

diff --git a/boost_ext/boost/parameter/aux_/unwrap_cv_reference.hpp b/boost_ext/boost/parameter/aux_/unwrap_cv_reference.hpp
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+++ b/boost_ext/boost/parameter/aux_/unwrap_cv_reference.hpp
@@ -0,0 +1,97 @@
+// Copyright Daniel Wallin, David Abrahams 2005. Use, modification and
+// distribution is subject to 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 UNWRAP_CV_REFERENCE_050328_HPP
+#define UNWRAP_CV_REFERENCE_050328_HPP
+
+#include <boost/parameter/aux_/yesno.hpp>
+#include <boost/mpl/bool.hpp>
+#include <boost/mpl/identity.hpp>
+#include <boost/mpl/eval_if.hpp>
+
+namespace boost { template<class T> class reference_wrapper; }
+
+namespace boost { namespace parameter { namespace aux {
+
+//
+// reference_wrapper support -- because of the forwarding problem,
+// when passing arguments positionally by non-const reference, we
+// ask users of named parameter interfaces to use ref(x) to wrap
+// them.
+//
+
+// is_cv_reference_wrapper returns mpl::true_ if T is of type
+// reference_wrapper<U> cv
+template <class U>
+yes_tag is_cv_reference_wrapper_check(reference_wrapper<U> const volatile*);
+no_tag is_cv_reference_wrapper_check(...);
+
+template <class T>
+struct is_cv_reference_wrapper
+{
+    BOOST_STATIC_CONSTANT(
+        bool, value = (
+            sizeof(is_cv_reference_wrapper_check((T*)0)) == sizeof(yes_tag)
+        )
+    );
+
+    typedef mpl::bool_<
+#if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564))
+        is_cv_reference_wrapper::
+#endif 
+    value> type;
+};
+
+#if BOOST_WORKAROUND(MSVC, == 1200)
+template <>
+struct is_cv_reference_wrapper<int>
+  : mpl::false_ {};
+#endif
+
+// Needed for unwrap_cv_reference below. T might be const, so
+// eval_if might fail because of deriving from T const on EDG.
+template <class T>
+struct get_type
+{
+    typedef typename T::type type;
+};
+
+#if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564))
+template <class T, class is_reference_wrapper = typename is_cv_reference_wrapper<T>::type>
+struct unwrap_cv_reference
+{
+    typedef T type;
+};
+
+template <class T>
+struct unwrap_cv_reference<T const, mpl::false_>
+{
+    typedef T const type;
+};
+
+template <class T>
+struct unwrap_cv_reference<T, mpl::true_>
+  : T
+{};
+
+#else 
+// Produces the unwrapped type to hold a reference to in named<>
+// Can't use boost::unwrap_reference<> here because it
+// doesn't handle the case where T = reference_wrapper<U> cv
+template <class T>
+struct unwrap_cv_reference
+{
+    typedef typename mpl::eval_if<
+        is_cv_reference_wrapper<T>
+      , get_type<T>
+      , mpl::identity<T>
+    >::type type;
+};
+#endif
+
+}}} // namespace boost::parameter::aux
+
+#endif // UNWRAP_CV_REFERENCE_050328_HPP
+