From d9c8ce2721c076805b541746d268e69a99e71bd9 Mon Sep 17 00:00:00 2001
From: Gerry Chen <gerry.chen2015@gmail.com>
Date: Thu, 2 Dec 2021 23:26:34 -0500
Subject: [PATCH] alternate make_index_sequence impl if no boost::mp11

---
 gtsam/nonlinear/NonlinearFactor.h | 34 +++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/gtsam/nonlinear/NonlinearFactor.h b/gtsam/nonlinear/NonlinearFactor.h
index b87d1bfaa..249891397 100644
--- a/gtsam/nonlinear/NonlinearFactor.h
+++ b/gtsam/nonlinear/NonlinearFactor.h
@@ -28,7 +28,41 @@
 
 #include <boost/serialization/base_object.hpp>
 #include <boost/assign/list_of.hpp>
+
+#if BOOST_VERSION >= 106600
 #include <boost/mp11/integer_sequence.hpp>
+#else
+namespace boost {
+namespace mp11 {
+// Adapted from https://stackoverflow.com/a/32223343/9151520
+template <size_t... Ints>
+struct index_sequence {
+  using type = index_sequence;
+  using value_type = size_t;
+  static constexpr std::size_t size() noexcept { return sizeof...(Ints); }
+};
+namespace detail {
+template <class Sequence1, class Sequence2>
+struct _merge_and_renumber;
+
+template <size_t... I1, size_t... I2>
+struct _merge_and_renumber<index_sequence<I1...>, index_sequence<I2...> >
+    : index_sequence<I1..., (sizeof...(I1) + I2)...> {};
+}  // namespace detail
+template <size_t N>
+struct make_index_sequence
+    : detail::_merge_and_renumber<
+          typename make_index_sequence<N / 2>::type,
+          typename make_index_sequence<N - N / 2>::type> {};
+template <>
+struct make_index_sequence<0> : index_sequence<> {};
+template <>
+struct make_index_sequence<1> : index_sequence<0> {};
+template <class... T>
+using index_sequence_for = make_index_sequence<sizeof...(T)>;
+}  // namespace mp11
+}  // namespace boost
+#endif
 
 namespace gtsam {