From 8a5097d726764674f4df38ffc953aad51210c967 Mon Sep 17 00:00:00 2001
From: Jose Luis Blanco Claraco <joseluisblancoc@gmail.com>
Date: Sun, 26 Jul 2020 08:22:40 +0200
Subject: [PATCH] Add docs on serializing expressions.

---
 gtsam/nonlinear/ExpressionFactor.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/gtsam/nonlinear/ExpressionFactor.h b/gtsam/nonlinear/ExpressionFactor.h
index c42b2bdfc..e39a65a0e 100644
--- a/gtsam/nonlinear/ExpressionFactor.h
+++ b/gtsam/nonlinear/ExpressionFactor.h
@@ -27,8 +27,13 @@
 namespace gtsam {
 
 /**
-
- * Factor that supports arbitrary expressions via AD
+ * Factor that supports arbitrary expressions via AD.
+ *
+ * Arbitrary instances of this template can be directly inserted into a factor
+ * graph for optimization. However, to enable the correct (de)serialization of
+ * such instances, the user should declare derived classes from this template,
+ * implementing expresion(), serialize(), clone(), print(), and defining the
+ * corresponding `struct traits<NewFactor> : public Testable<NewFactor> {}`.
  */
 template<typename T>
 class ExpressionFactor: public NoiseModelFactor {