DER encoding: implement VoidVisitor and NoArgumentsVisitor
diff --git a/ndn-cpp/encoding/der/visitor/no-arguments-visitor.cpp b/ndn-cpp/encoding/der/visitor/no-arguments-visitor.cpp
new file mode 100644
index 0000000..3ea819d
--- /dev/null
+++ b/ndn-cpp/encoding/der/visitor/no-arguments-visitor.cpp
@@ -0,0 +1,53 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
+/**
+ * Copyright (C) 2013 Regents of the University of California.
+ * @author: Yingdi Yu <yingdi@cs.ucla.edu>
+ * @author: Jeff Thompson <jefft0@remap.ucla.edu>
+ * See COPYING for copyright and distribution information.
+ */
+
+#include "no-arguments-visitor.hpp"
+
+namespace ndn {
+
+namespace der
+{
+Any
+NoArgumentsVisitor::visit(DerBool& derBool)
+{ return Any(0); }
+
+Any
+NoArgumentsVisitor::visit(DerInteger& derInteger)
+{ return Any(0); }
+
+Any
+NoArgumentsVisitor::visit(DerPrintableString& derPStr)
+{ return Any(0); }
+
+Any
+NoArgumentsVisitor::visit(DerBitString& derBStr)
+{ return Any(0); }
+
+Any
+NoArgumentsVisitor::visit(DerNull& derNull)
+{ return Any(0); }
+
+Any
+NoArgumentsVisitor::visit(DerOctetString& derOStr)
+{ return Any(0); }
+
+Any
+NoArgumentsVisitor::visit(DerOid& derOid)
+{ return Any(0); }
+
+Any
+NoArgumentsVisitor::visit(DerSequence& derSeq)
+{ return Any(0); }
+
+Any
+NoArgumentsVisitor::visit(DerGtime& derGtime)
+{ return Any(0); }
+
+} // der
+
+}