From 93ec276ef3090c46a13307c6c777b51f84f308aa Mon Sep 17 00:00:00 2001
From: Varun Agrawal <varagrawal@gmail.com>
Date: Wed, 9 Oct 2024 13:47:59 -0400
Subject: [PATCH] implement dummy >> operator

---
 gtsam/hybrid/HybridGaussianProductFactor.cpp |  6 ++++++
 gtsam/hybrid/HybridGaussianProductFactor.h   | 20 ++++++++++++--------
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/gtsam/hybrid/HybridGaussianProductFactor.cpp b/gtsam/hybrid/HybridGaussianProductFactor.cpp
index f7b5994f0f..280059f542 100644
--- a/gtsam/hybrid/HybridGaussianProductFactor.cpp
+++ b/gtsam/hybrid/HybridGaussianProductFactor.cpp
@@ -103,4 +103,10 @@ HybridGaussianProductFactor HybridGaussianProductFactor::removeEmpty() const {
   return {Base(*this, emptyGaussian)};
 }
 
+/* *******************************************************************************/
+std::istream& operator>>(std::istream& is, GaussianFactorGraphValuePair& pair) {
+  // Dummy, don't do anything
+  return is;
+}
+
 }  // namespace gtsam
diff --git a/gtsam/hybrid/HybridGaussianProductFactor.h b/gtsam/hybrid/HybridGaussianProductFactor.h
index ab15fee303..60a58a3a51 100644
--- a/gtsam/hybrid/HybridGaussianProductFactor.h
+++ b/gtsam/hybrid/HybridGaussianProductFactor.h
@@ -22,6 +22,8 @@
 #include <gtsam/inference/Key.h>
 #include <gtsam/linear/GaussianFactorGraph.h>
 
+#include <iostream>
+
 namespace gtsam {
 
 class HybridGaussianFactor;
@@ -55,14 +57,6 @@ class GTSAM_EXPORT HybridGaussianProductFactor
    */
   HybridGaussianProductFactor(Base&& tree) : Base(std::move(tree)) {}
 
-  /// Deleted constructor since we don't have istream operator for
-  /// GaussianFactorGraphValuePair
-  HybridGaussianProductFactor(const std::vector<DiscreteKey>& labelCs,
-                              const std::string& table) {
-    throw std::runtime_error(
-        "HybridGaussianProductFactor: No way to construct.");
-  }
-
   ///@}
 
   /// @name Operators
@@ -140,4 +134,14 @@ template <>
 struct traits<HybridGaussianProductFactor>
     : public Testable<HybridGaussianProductFactor> {};
 
+/**
+ * Create a dummy overload of >> for GaussianFactorGraphValuePair
+ * so that HybridGaussianProductFactor compiles
+ * with the constructor
+ * `DecisionTree(const std::vector<LabelC>& labelCs, const std::string& table)`.
+ *
+ * Needed to compile on Windows.
+ */
+std::istream& operator>>(std::istream& is, GaussianFactorGraphValuePair& pair);
+
 }  // namespace gtsam