diff --git a/gtsam/discrete/DecisionTreeFactor.cpp b/gtsam/discrete/DecisionTreeFactor.cpp
index 9ec3b0ac5..a57915e45 100644
--- a/gtsam/discrete/DecisionTreeFactor.cpp
+++ b/gtsam/discrete/DecisionTreeFactor.cpp
@@ -195,7 +195,7 @@ namespace gtsam {
     // Construct unordered_map with values
     std::vector<std::pair<DiscreteValues, double>> result;
     for (const auto& assignment : assignments) {
-      result.emplace_back(assignment, operator()(assignment));
+      result.emplace_back(assignment, evaluate(assignment));
     }
     return result;
   }
diff --git a/gtsam/discrete/DecisionTreeFactor.h b/gtsam/discrete/DecisionTreeFactor.h
index 9a3cde96d..741715e43 100644
--- a/gtsam/discrete/DecisionTreeFactor.h
+++ b/gtsam/discrete/DecisionTreeFactor.h
@@ -130,16 +130,14 @@ namespace gtsam {
     /// @name Standard Interface
     /// @{
 
-    /// Calculate probability for given values `x`, 
+    /// Calculate probability for given values, 
     /// is just look up in AlgebraicDecisionTree.
-    double evaluate(const Assignment<Key>& values) const  {
+    virtual double evaluate(const Assignment<Key>& values) const override {
       return ADT::operator()(values);
     }
 
-    /// Evaluate probability distribution, sugar.
-    double operator()(const DiscreteValues& values) const override {
-      return ADT::operator()(values);
-    }
+    /// Disambiguate to use DiscreteFactor version. Mainly for wrapper
+    using DiscreteFactor::operator();
 
     /// Calculate error for DiscreteValues `x`, is -log(probability).
     double error(const DiscreteValues& values) const override;
diff --git a/gtsam/discrete/DiscreteConditional.h b/gtsam/discrete/DiscreteConditional.h
index f59e29285..858623301 100644
--- a/gtsam/discrete/DiscreteConditional.h
+++ b/gtsam/discrete/DiscreteConditional.h
@@ -169,12 +169,12 @@ class GTSAM_EXPORT DiscreteConditional
   }
 
   /// Evaluate, just look up in AlgebraicDecisionTree
-  double evaluate(const DiscreteValues& values) const {
+  virtual double evaluate(const Assignment<Key>& values) const override {
     return ADT::operator()(values);
   }
 
   using DecisionTreeFactor::error;       ///< DiscreteValues version
-  using DecisionTreeFactor::operator();  ///< DiscreteValues version
+  using DiscreteFactor::operator();      ///< DiscreteValues version
 
   /**
    * @brief restrict to given *parent* values.
diff --git a/gtsam/discrete/DiscreteFactor.h b/gtsam/discrete/DiscreteFactor.h
index 19af5bd13..2ba670004 100644
--- a/gtsam/discrete/DiscreteFactor.h
+++ b/gtsam/discrete/DiscreteFactor.h
@@ -92,8 +92,21 @@ class GTSAM_EXPORT DiscreteFactor : public Factor {
 
   size_t cardinality(Key j) const { return cardinalities_.at(j); }
 
+  /**
+   * @brief Calculate probability for given values.
+   * Calls specialized evaluation under the hood.
+   *
+   * Note: Uses Assignment<Key> as it is the base class of DiscreteValues.
+   *
+   * @param values Discrete assignment.
+   * @return double
+   */
+  virtual double evaluate(const Assignment<Key>& values) const = 0;
+
   /// Find value for given assignment of values to variables
-  virtual double operator()(const DiscreteValues&) const = 0;
+  double operator()(const DiscreteValues& values) const {
+    return evaluate(values);
+  }
 
   /// Error is just -log(value)
   virtual double error(const DiscreteValues& values) const;
diff --git a/gtsam/discrete/TableFactor.cpp b/gtsam/discrete/TableFactor.cpp
index f4e023a4d..ea51a996c 100644
--- a/gtsam/discrete/TableFactor.cpp
+++ b/gtsam/discrete/TableFactor.cpp
@@ -133,7 +133,7 @@ bool TableFactor::equals(const DiscreteFactor& other, double tol) const {
 }
 
 /* ************************************************************************ */
-double TableFactor::operator()(const DiscreteValues& values) const {
+double TableFactor::evaluate(const Assignment<Key>& values) const {
   // a b c d => D * (C * (B * (a) + b) + c) + d
   uint64_t idx = 0, card = 1;
   for (auto it = sorted_dkeys_.rbegin(); it != sorted_dkeys_.rend(); ++it) {
@@ -180,6 +180,7 @@ DecisionTreeFactor TableFactor::toDecisionTreeFactor() const {
   for (auto i = 0; i < sparse_table_.size(); i++) {
     table.push_back(sparse_table_.coeff(i));
   }
+  // NOTE(Varun): This constructor is really expensive!!
   DecisionTreeFactor f(dkeys, table);
   return f;
 }
diff --git a/gtsam/discrete/TableFactor.h b/gtsam/discrete/TableFactor.h
index 7015353e1..1aecc1669 100644
--- a/gtsam/discrete/TableFactor.h
+++ b/gtsam/discrete/TableFactor.h
@@ -155,14 +155,8 @@ class GTSAM_EXPORT TableFactor : public DiscreteFactor {
   // /// @name Standard Interface
   // /// @{
 
-  /// Calculate probability for given values `x`,
-  /// is just look up in TableFactor.
-  double evaluate(const DiscreteValues& values) const {
-    return operator()(values);
-  }
-
-  /// Evaluate probability distribution, sugar.
-  double operator()(const DiscreteValues& values) const override;
+  /// Evaluate probability distribution, is just look up in TableFactor.
+  double evaluate(const Assignment<Key>& values) const override;
 
   /// Calculate error for DiscreteValues `x`, is -log(probability).
   double error(const DiscreteValues& values) const override;
diff --git a/gtsam/discrete/discrete.i b/gtsam/discrete/discrete.i
index 55c8f9e22..b2e2524f8 100644
--- a/gtsam/discrete/discrete.i
+++ b/gtsam/discrete/discrete.i
@@ -61,14 +61,14 @@ virtual class DecisionTreeFactor : gtsam::DiscreteFactor {
   DecisionTreeFactor(const std::vector<gtsam::DiscreteKey>& keys, string table);
 
   DecisionTreeFactor(const gtsam::DiscreteConditional& c);
-  
+
   void print(string s = "DecisionTreeFactor\n",
              const gtsam::KeyFormatter& keyFormatter =
                  gtsam::DefaultKeyFormatter) const;
   bool equals(const gtsam::DecisionTreeFactor& other, double tol = 1e-9) const;
 
   size_t cardinality(gtsam::Key j) const;
-  
+
   double operator()(const gtsam::DiscreteValues& values) const;
   gtsam::DecisionTreeFactor operator*(const gtsam::DecisionTreeFactor& f) const;
   size_t cardinality(gtsam::Key j) const;
diff --git a/gtsam_unstable/discrete/AllDiff.cpp b/gtsam_unstable/discrete/AllDiff.cpp
index 2bd9e6dfd..585ca8103 100644
--- a/gtsam_unstable/discrete/AllDiff.cpp
+++ b/gtsam_unstable/discrete/AllDiff.cpp
@@ -26,7 +26,7 @@ void AllDiff::print(const std::string& s, const KeyFormatter& formatter) const {
 }
 
 /* ************************************************************************* */
-double AllDiff::operator()(const DiscreteValues& values) const {
+double AllDiff::evaluate(const Assignment<Key>& values) const {
   std::set<size_t> taken;  // record values taken by keys
   for (Key dkey : keys_) {
     size_t value = values.at(dkey);      // get the value for that key
diff --git a/gtsam_unstable/discrete/AllDiff.h b/gtsam_unstable/discrete/AllDiff.h
index d7a63eae0..1180abad4 100644
--- a/gtsam_unstable/discrete/AllDiff.h
+++ b/gtsam_unstable/discrete/AllDiff.h
@@ -45,7 +45,7 @@ class GTSAM_UNSTABLE_EXPORT AllDiff : public Constraint {
   }
 
   /// Calculate value = expensive !
-  double operator()(const DiscreteValues& values) const override;
+  double evaluate(const Assignment<Key>& values) const override;
 
   /// Convert into a decisiontree, can be *very* expensive !
   DecisionTreeFactor toDecisionTreeFactor() const override;
diff --git a/gtsam_unstable/discrete/BinaryAllDiff.h b/gtsam_unstable/discrete/BinaryAllDiff.h
index 18b335092..e96bfdfde 100644
--- a/gtsam_unstable/discrete/BinaryAllDiff.h
+++ b/gtsam_unstable/discrete/BinaryAllDiff.h
@@ -47,7 +47,7 @@ class BinaryAllDiff : public Constraint {
   }
 
   /// Calculate value
-  double operator()(const DiscreteValues& values) const override {
+  double evaluate(const Assignment<Key>& values) const override {
     return (double)(values.at(keys_[0]) != values.at(keys_[1]));
   }
 
diff --git a/gtsam_unstable/discrete/Domain.cpp b/gtsam_unstable/discrete/Domain.cpp
index bbbc87667..74f621dc7 100644
--- a/gtsam_unstable/discrete/Domain.cpp
+++ b/gtsam_unstable/discrete/Domain.cpp
@@ -30,7 +30,7 @@ string Domain::base1Str() const {
 }
 
 /* ************************************************************************* */
-double Domain::operator()(const DiscreteValues& values) const {
+double Domain::evaluate(const Assignment<Key>& values) const {
   return contains(values.at(key()));
 }
 
diff --git a/gtsam_unstable/discrete/Domain.h b/gtsam_unstable/discrete/Domain.h
index 7f7b717c2..23a566d24 100644
--- a/gtsam_unstable/discrete/Domain.h
+++ b/gtsam_unstable/discrete/Domain.h
@@ -82,7 +82,7 @@ class GTSAM_UNSTABLE_EXPORT Domain : public Constraint {
   bool contains(size_t value) const { return values_.count(value) > 0; }
 
   /// Calculate value
-  double operator()(const DiscreteValues& values) const override;
+  double evaluate(const Assignment<Key>& values) const override;
 
   /// Convert into a decisiontree
   DecisionTreeFactor toDecisionTreeFactor() const override;
diff --git a/gtsam_unstable/discrete/SingleValue.cpp b/gtsam_unstable/discrete/SingleValue.cpp
index 6b78f38f5..220bc9c06 100644
--- a/gtsam_unstable/discrete/SingleValue.cpp
+++ b/gtsam_unstable/discrete/SingleValue.cpp
@@ -22,7 +22,7 @@ void SingleValue::print(const string& s, const KeyFormatter& formatter) const {
 }
 
 /* ************************************************************************* */
-double SingleValue::operator()(const DiscreteValues& values) const {
+double SingleValue::evaluate(const Assignment<Key>& values) const {
   return (double)(values.at(keys_[0]) == value_);
 }
 
diff --git a/gtsam_unstable/discrete/SingleValue.h b/gtsam_unstable/discrete/SingleValue.h
index 3f7f22d6a..3df1209b8 100644
--- a/gtsam_unstable/discrete/SingleValue.h
+++ b/gtsam_unstable/discrete/SingleValue.h
@@ -55,7 +55,7 @@ class GTSAM_UNSTABLE_EXPORT SingleValue : public Constraint {
   }
 
   /// Calculate value
-  double operator()(const DiscreteValues& values) const override;
+  double evaluate(const Assignment<Key>& values) const override;
 
   /// Convert into a decisiontree
   DecisionTreeFactor toDecisionTreeFactor() const override;
diff --git a/python/gtsam/tests/test_DecisionTreeFactor.py b/python/gtsam/tests/test_DecisionTreeFactor.py
index 12308bb3c..a78d9c94a 100644
--- a/python/gtsam/tests/test_DecisionTreeFactor.py
+++ b/python/gtsam/tests/test_DecisionTreeFactor.py
@@ -13,9 +13,10 @@ Author: Frank Dellaert
 
 import unittest
 
+from gtsam.utils.test_case import GtsamTestCase
+
 from gtsam import (DecisionTreeFactor, DiscreteDistribution, DiscreteValues,
                    Ordering)
-from gtsam.utils.test_case import GtsamTestCase
 
 
 class TestDecisionTreeFactor(GtsamTestCase):
diff --git a/python/gtsam/tests/test_DiscreteBayesTree.py b/python/gtsam/tests/test_DiscreteBayesTree.py
index 2a9b6ea09..e08491fab 100644
--- a/python/gtsam/tests/test_DiscreteBayesTree.py
+++ b/python/gtsam/tests/test_DiscreteBayesTree.py
@@ -19,8 +19,8 @@ from gtsam.utils.test_case import GtsamTestCase
 
 import gtsam
 from gtsam import (DiscreteBayesNet, DiscreteBayesTreeClique,
-                   DiscreteConditional, DiscreteFactorGraph,
-                   DiscreteValues, Ordering)
+                   DiscreteConditional, DiscreteFactorGraph, DiscreteValues,
+                   Ordering)
 
 
 class TestDiscreteBayesNet(GtsamTestCase):
diff --git a/python/gtsam/tests/test_DiscreteConditional.py b/python/gtsam/tests/test_DiscreteConditional.py
index 241a5f0be..6c9eb9aec 100644
--- a/python/gtsam/tests/test_DiscreteConditional.py
+++ b/python/gtsam/tests/test_DiscreteConditional.py
@@ -13,9 +13,10 @@ Author: Varun Agrawal
 
 import unittest
 
-from gtsam import DecisionTreeFactor, DiscreteConditional, DiscreteKeys
 from gtsam.utils.test_case import GtsamTestCase
 
+from gtsam import DecisionTreeFactor, DiscreteConditional, DiscreteKeys
+
 # Some DiscreteKeys for binary variables:
 A = 0, 2
 B = 1, 2
diff --git a/python/gtsam/tests/test_DiscreteFactorGraph.py b/python/gtsam/tests/test_DiscreteFactorGraph.py
index d725ceac8..3053087b4 100644
--- a/python/gtsam/tests/test_DiscreteFactorGraph.py
+++ b/python/gtsam/tests/test_DiscreteFactorGraph.py
@@ -14,9 +14,12 @@ Author: Frank Dellaert
 import unittest
 
 import numpy as np
-from gtsam import DecisionTreeFactor, DiscreteConditional, DiscreteFactorGraph, DiscreteKeys, DiscreteValues, Ordering, Symbol
 from gtsam.utils.test_case import GtsamTestCase
 
+from gtsam import (DecisionTreeFactor, DiscreteConditional,
+                   DiscreteFactorGraph, DiscreteKeys, DiscreteValues, Ordering,
+                   Symbol)
+
 OrderingType = Ordering.OrderingType