Imported existing code

libraries/include/boost/flyweight/detail/is_placeholder_expr.hpp

@@ -0,0 +1,65 @@
+/* Copyright 2006-2009 Joaquin M Lopez Munoz.
+ * 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)
+ *
+ * See http://www.boost.org/libs/flyweight for library home page.
+ */
+
+#ifndef BOOST_FLYWEIGHT_DETAIL_IS_PLACEHOLDER_EXPR_HPP
+#define BOOST_FLYWEIGHT_DETAIL_IS_PLACEHOLDER_EXPR_HPP
+
+#if defined(_MSC_VER)&&(_MSC_VER>=1200)
+#pragma once
+#endif
+
+#include <boost/type_traits/is_same.hpp>
+#include <boost/mpl/apply.hpp>
+#include <boost/mpl/aux_/lambda_support.hpp>
+#include <boost/mpl/not.hpp>
+#include <boost/preprocessor/facilities/intercept.hpp>
+#include <boost/preprocessor/repetition/enum_params.hpp>
+
+namespace boost{
+
+namespace flyweights{
+
+namespace detail{
+
+/* is_placeholder_expression<T> indicates whether T is an
+ * MPL placeholder expression.
+ */
+
+template<typename T>
+struct is_placeholder_expression_helper
+{
+  template<
+    BOOST_PP_ENUM_PARAMS(
+      BOOST_MPL_LIMIT_METAFUNCTION_ARITY,typename BOOST_PP_INTERCEPT)
+  >
+  struct apply{
+    typedef int type;
+  };
+
+  BOOST_MPL_AUX_LAMBDA_SUPPORT(1,is_placeholder_expression_helper,(T))
+};
+
+template<typename T>
+struct is_placeholder_expression:
+  mpl::not_<is_same<
+    typename mpl::apply<
+      is_placeholder_expression_helper<T>,
+      BOOST_PP_ENUM_PARAMS(
+        BOOST_MPL_LIMIT_METAFUNCTION_ARITY,int BOOST_PP_INTERCEPT)
+    >::type,
+    int
+  > >
+{};
+
+} /* namespace flyweights::detail */
+
+} /* namespace flyweights */
+
+} /* namespace boost */
+
+#endif