From b52f488d7572fe0f1982ddf7991902e2ec660bab Mon Sep 17 00:00:00 2001
From: Frank Dellaert <frank@skyd.io>
Date: Sat, 11 Jul 2015 13:51:39 -0700
Subject: [PATCH] default constructor

---
 gtsam/nonlinear/Expression.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/gtsam/nonlinear/Expression.h b/gtsam/nonlinear/Expression.h
index 4fdbe8610..0b348ece9 100644
--- a/gtsam/nonlinear/Expression.h
+++ b/gtsam/nonlinear/Expression.h
@@ -172,6 +172,9 @@ public:
 
 private:
 
+  /// Default constructor, for serialization
+  Expression() {}
+
   /// Keys and dimensions in same order
   typedef std::pair<KeyVector, FastVector<int> > KeysAndDims;
   KeysAndDims keysAndDims() const;