From 39371eb343f57aeef00f8769fc3434ce76471dae Mon Sep 17 00:00:00 2001
From: Francesco Biscani <Francesco.Biscani@ext.esa.int>
Date: Sun, 10 Sep 2023 20:16:43 +0000
Subject: [PATCH] Initial files for cr3bp.

---
 include/heyoka/kw.hpp          |  1 +
 include/heyoka/model/cr3bp.hpp | 67 ++++++++++++++++++++++++++++++++++
 include/heyoka/models.hpp      |  1 +
 3 files changed, 69 insertions(+)
 create mode 100644 include/heyoka/model/cr3bp.hpp

diff --git a/include/heyoka/kw.hpp b/include/heyoka/kw.hpp
index 0a2c00eea..c28481287 100644
--- a/include/heyoka/kw.hpp
+++ b/include/heyoka/kw.hpp
@@ -28,6 +28,7 @@ IGOR_MAKE_NAMED_ARGUMENT(compact_mode);
 IGOR_MAKE_NAMED_ARGUMENT(high_accuracy);
 IGOR_MAKE_NAMED_ARGUMENT(parallel_mode);
 IGOR_MAKE_NAMED_ARGUMENT(prec);
+IGOR_MAKE_NAMED_ARGUMENT(mu);
 
 } // namespace kw
 
diff --git a/include/heyoka/model/cr3bp.hpp b/include/heyoka/model/cr3bp.hpp
new file mode 100644
index 000000000..037c9738d
--- /dev/null
+++ b/include/heyoka/model/cr3bp.hpp
@@ -0,0 +1,67 @@
+// Copyright 2020, 2021, 2022, 2023 Francesco Biscani (bluescarni@gmail.com), Dario Izzo (dario.izzo@gmail.com)
+//
+// This file is part of the heyoka library.
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef HEYOKA_MODEL_CR3BP_HPP
+#define HEYOKA_MODEL_CR3BP_HPP
+
+#include <tuple>
+#include <utility>
+#include <vector>
+
+#include <heyoka/config.hpp>
+#include <heyoka/detail/igor.hpp>
+#include <heyoka/detail/visibility.hpp>
+#include <heyoka/expression.hpp>
+#include <heyoka/kw.hpp>
+
+HEYOKA_BEGIN_NAMESPACE
+
+namespace model
+{
+
+namespace detail
+{
+
+template <typename... KwArgs>
+auto cr3bp_common_opts(KwArgs &&...kw_args)
+{
+    igor::parser p{kw_args...};
+
+    static_assert(!p.has_unnamed_arguments(), "This function accepts only named arguments");
+
+    expression mu{1e-3};
+    if constexpr (p.has(kw::mu)) {
+        mu = expression{std::forward<decltype(p(kw::mu))>(p(kw::mu))};
+    }
+
+    return std::tuple{std::move(mu)};
+}
+
+HEYOKA_DLL_PUBLIC std::vector<std::pair<expression, expression>> cr3bp_impl(const expression &);
+
+HEYOKA_DLL_PUBLIC expression cr3bp_jacobi_impl(const expression &);
+
+} // namespace detail
+
+// NOTE: non-dimensional c3bp dynamics in the usual rotating (synodic) reference frame.
+// Expressed in terms of canonical state variables.
+inline constexpr auto cr3bp = [](auto &&...kw_args) -> std::vector<std::pair<expression, expression>> {
+    return std::apply(detail::cr3bp_impl, detail::cr3bp_common_opts(std::forward<decltype(kw_args)>(kw_args)...));
+};
+
+// NOTE: this returns a specific energy.
+inline constexpr auto cr3bp_jacobi = [](auto &&...kw_args) -> expression {
+    return std::apply(detail::cr3bp_jacobi_impl,
+                      detail::cr3bp_common_opts(std::forward<decltype(kw_args)>(kw_args)...));
+};
+
+} // namespace model
+
+HEYOKA_END_NAMESPACE
+
+#endif
diff --git a/include/heyoka/models.hpp b/include/heyoka/models.hpp
index 37ff4032f..12b11a67f 100644
--- a/include/heyoka/models.hpp
+++ b/include/heyoka/models.hpp
@@ -9,6 +9,7 @@
 #ifndef HEYOKA_MODELS_HPP
 #define HEYOKA_MODELS_HPP
 
+#include <heyoka/model/cr3bp.hpp>
 #include <heyoka/model/fixed_centres.hpp>
 #include <heyoka/model/mascon.hpp>
 #include <heyoka/model/nbody.hpp>