diff --git a/libs/functional/overloaded_function/test/identity.hpp b/libs/functional/overloaded_function/test/identity.hpp
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+
+// Copyright (C) 2009-2012 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0
+// (see accompanying file LICENSE_1_0.txt or a copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+// Home at http://www.boost.org/libs/functional/overloaded_function
+
+#ifndef IDENTITY_HPP_
+#define IDENTITY_HPP_
+
+//[identity_typeof
+#include <boost/typeof/std/string.hpp> // No need to register `ndnboost::function`.
+//]
+#include <boost/function.hpp>
+#include <string>
+
+//[identity_decls
+const std::string& identity_s(const std::string& x) // Function (as pointer).
+    { return x; }
+
+int identity_i_impl(int x) { return x; }
+int (&identity_i)(int) = identity_i_impl; // Function reference.
+
+double identity_d_impl(double x) { return x; }
+ndnboost::function<double (double)> identity_d = identity_d_impl; // Functor.
+//]
+
+#endif // #include guard
+