Used Boost.MPL to make the char value from a TypedSymbol available as a type to templated functions/classes

gtsam/nonlinear/Key.h

@@ -22,6 +22,7 @@
 #include <vector>
 #include <list>
 #include <iostream>
+#include <boost/mpl/char.hpp>
 #include <boost/format.hpp>
 #include <boost/serialization/nvp.hpp>
 #ifdef GTSAM_MAGIC_KEY
@@ -49,6 +50,7 @@ public:
 
   // typedefs
   typedef T Value;
+  typedef boost::mpl::char_<C> Chr;  // to reconstruct the type: use Chr::value
 
   // Constructors:
 

gtsam/nonlinear/tests/testKey.cpp

@@ -99,6 +99,13 @@ TEST ( TypedLabledSymbol, encoding ) {
 	CHECK(assert_equal(key1, RobotKey(act1)));
 }
 
+/* ************************************************************************* */
+TEST ( TypedLabledSymbol, template_reconstruction ) {
+	typedef TypedSymbol<Pose3, 'x'> Key;
+	typedef TypedLabeledSymbol<Key::Value, Key::Chr::value, char> NewKey;
+	NewKey k(1, 'A');
+}
+
 /* ************************************************************************* */
 TEST ( Key, keys2symbols )
 {