diff --git a/gtsam/discrete/DecisionTreeFactor.cpp b/gtsam/discrete/DecisionTreeFactor.cpp
index 7f566a115..bb83cec16 100644
--- a/gtsam/discrete/DecisionTreeFactor.cpp
+++ b/gtsam/discrete/DecisionTreeFactor.cpp
@@ -49,10 +49,11 @@ namespace gtsam {
 	}
 
 	/* ************************************************************************* */
-	void DecisionTreeFactor::print(const string& s) const {
+	void DecisionTreeFactor::print(const string& s,
+			const IndexFormatter& formatter) const {
 		cout << s;
-		IndexFactor::print("IndexFactor:");
-		Potentials::print("Potentials:");
+		IndexFactor::print("IndexFactor:",formatter);
+		Potentials::print("Potentials:",formatter);
 	}
 
 	/* ************************************************************************* */
diff --git a/gtsam/discrete/DecisionTreeFactor.h b/gtsam/discrete/DecisionTreeFactor.h
index 89bc090dc..64f37c174 100644
--- a/gtsam/discrete/DecisionTreeFactor.h
+++ b/gtsam/discrete/DecisionTreeFactor.h
@@ -72,7 +72,8 @@ namespace gtsam {
 		bool equals(const DecisionTreeFactor& other, double tol = 1e-9) const;
 
 		// print
-		void print(const std::string& s = "DecisionTreeFactor:\n") const;
+		virtual void print(const std::string& s = "DecisionTreeFactor:\n",
+				const IndexFormatter& formatter = DefaultIndexFormatter) const;
 
 		/// @}
 		/// @name Standard Interface
diff --git a/gtsam/discrete/Potentials.cpp b/gtsam/discrete/Potentials.cpp
index b9a87dea9..2a2260d97 100644
--- a/gtsam/discrete/Potentials.cpp
+++ b/gtsam/discrete/Potentials.cpp
@@ -51,10 +51,11 @@ namespace gtsam {
 	}
 
 	/* ************************************************************************* */
-	void Potentials::print(const string&s) const {
+	void Potentials::print(const string& s,
+			const IndexFormatter& formatter) const {
 		cout << s << "\n  Cardinalities: ";
 		BOOST_FOREACH(const DiscreteKey& key, cardinalities_)
-			cout << key.first << "=" << key.second << " ";
+			cout << formatter(key.first) << "=" << formatter(key.second) << " ";
 		cout << endl;
 		ADT::print(" ");
 	}
diff --git a/gtsam/discrete/Potentials.h b/gtsam/discrete/Potentials.h
index 367a323c2..3ca222b5f 100644
--- a/gtsam/discrete/Potentials.h
+++ b/gtsam/discrete/Potentials.h
@@ -65,7 +65,8 @@ namespace gtsam {
 
 		// Testable
 		bool equals(const Potentials& other, double tol = 1e-9) const;
-		void print(const std::string& s = "Potentials: ") const;
+		void print(const std::string& s = "Potentials: ",
+				const IndexFormatter& formatter = DefaultIndexFormatter) const;
 
 		size_t cardinality(Index j) const { return cardinalities_.at(j);}
 
diff --git a/gtsam_unstable/discrete/AllDiff.cpp b/gtsam_unstable/discrete/AllDiff.cpp
index 41905f874..ac412fa7f 100644
--- a/gtsam_unstable/discrete/AllDiff.cpp
+++ b/gtsam_unstable/discrete/AllDiff.cpp
@@ -20,10 +20,11 @@ namespace gtsam {
 	}
 
 	/* ************************************************************************* */
-	void AllDiff::print(const std::string& s) const {
+	void AllDiff::print(const std::string& s,
+			const IndexFormatter& formatter) const {
 		std::cout << s << "AllDiff on ";
 		BOOST_FOREACH (Index dkey, keys_)
-			std::cout << dkey << " ";
+			std::cout << formatter(dkey) << " ";
 		std::cout << std::endl;
 	}
 
diff --git a/gtsam_unstable/discrete/AllDiff.h b/gtsam_unstable/discrete/AllDiff.h
index fb5a47a59..1a560ace2 100644
--- a/gtsam_unstable/discrete/AllDiff.h
+++ b/gtsam_unstable/discrete/AllDiff.h
@@ -34,7 +34,8 @@ namespace gtsam {
 		AllDiff(const DiscreteKeys& dkeys);
 
 		// print
-		virtual void print(const std::string& s = "") const;
+		virtual void print(const std::string& s = "",
+				const IndexFormatter& formatter = DefaultIndexFormatter) const;
 
 		/// Calculate value = expensive !
 		virtual double operator()(const Values& values) const;
diff --git a/gtsam_unstable/discrete/BinaryAllDiff.h b/gtsam_unstable/discrete/BinaryAllDiff.h
index a2e260bcd..9ed2f79f1 100644
--- a/gtsam_unstable/discrete/BinaryAllDiff.h
+++ b/gtsam_unstable/discrete/BinaryAllDiff.h
@@ -33,9 +33,10 @@ namespace gtsam {
 		}
 
 		// print
-		virtual void print(const std::string& s = "") const {
-			std::cout << s << "BinaryAllDiff on " << keys_[0] << " and " << keys_[1]
-					<< std::endl;
+		virtual void print(const std::string& s = "",
+				const IndexFormatter& formatter = DefaultIndexFormatter) const {
+			std::cout << s << "BinaryAllDiff on " << formatter(keys_[0]) << " and "
+					<< formatter(keys_[1]) << std::endl;
 		}
 
 		/// Calculate value
diff --git a/gtsam_unstable/discrete/Domain.cpp b/gtsam_unstable/discrete/Domain.cpp
index e43065f3b..dbc05e3f6 100644
--- a/gtsam_unstable/discrete/Domain.cpp
+++ b/gtsam_unstable/discrete/Domain.cpp
@@ -15,9 +15,10 @@ namespace gtsam {
 	using namespace std;
 
 	/* ************************************************************************* */
-	void Domain::print(const string& s) const {
-//		cout << s << ": Domain on " << keys_[0] << " (j=" << keys_[0]
-//				<< ") with values";
+	void Domain::print(const string& s,
+			const IndexFormatter& formatter) const {
+//		cout << s << ": Domain on " << formatter(keys_[0]) << " (j=" <<
+//		formatter(keys_[0]) << ") with values";
 //		BOOST_FOREACH (size_t v,values_) cout << " " << v;
 //		cout << endl;
 		BOOST_FOREACH (size_t v,values_) cout << v;
diff --git a/gtsam_unstable/discrete/Domain.h b/gtsam_unstable/discrete/Domain.h
index a4f0c8054..85b35fe8c 100644
--- a/gtsam_unstable/discrete/Domain.h
+++ b/gtsam_unstable/discrete/Domain.h
@@ -66,7 +66,8 @@ namespace gtsam {
 		}
 
 		// print
-		virtual void print(const std::string& s = "") const;
+		virtual void print(const std::string& s = "",
+				const IndexFormatter& formatter = DefaultIndexFormatter) const;
 
 		bool contains(size_t value) const {
 			return values_.count(value)>0;
diff --git a/gtsam_unstable/discrete/SingleValue.cpp b/gtsam_unstable/discrete/SingleValue.cpp
index 6f6d5a3ff..81133e7f7 100644
--- a/gtsam_unstable/discrete/SingleValue.cpp
+++ b/gtsam_unstable/discrete/SingleValue.cpp
@@ -16,8 +16,9 @@ namespace gtsam {
 	using namespace std;
 
 	/* ************************************************************************* */
-	void SingleValue::print(const string& s) const {
-		cout << s << "SingleValue on " << "j=" << keys_[0]
+	void SingleValue::print(const string& s,
+			const IndexFormatter& formatter) const {
+		cout << s << "SingleValue on " << "j=" << formatter(keys_[0])
 				<< " with value " << value_ << endl;
 	}
 
diff --git a/gtsam_unstable/discrete/SingleValue.h b/gtsam_unstable/discrete/SingleValue.h
index b229d8b79..1f6e362aa 100644
--- a/gtsam_unstable/discrete/SingleValue.h
+++ b/gtsam_unstable/discrete/SingleValue.h
@@ -42,7 +42,8 @@ namespace gtsam {
 		}
 
 		// print
-		virtual void print(const std::string& s = "") const;
+		virtual void print(const std::string& s = "",
+				const IndexFormatter& formatter = DefaultIndexFormatter) const;
 
 		/// Calculate value
 		virtual double operator()(const Values& values) const;