From c430b993b77089f584c39b2a6f62b961f5b01189 Mon Sep 17 00:00:00 2001
From: Helge Eichhorn <git@helgeeichhorn.de>
Date: Mon, 22 Jan 2024 15:08:55 +0100
Subject: [PATCH] Re-add TwoBody trait

---
 crates/lox_core/src/coords.rs | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/crates/lox_core/src/coords.rs b/crates/lox_core/src/coords.rs
index 6014e8e4..d0a1f59f 100644
--- a/crates/lox_core/src/coords.rs
+++ b/crates/lox_core/src/coords.rs
@@ -26,6 +26,16 @@ pub trait CoordinateSystem {
     fn reference_frame(&self) -> Self::Frame;
 }
 
+pub trait TwoBody<T, S>
+where
+    T: PointMass + Copy,
+    S: InertialFrame + Copy,
+{
+    fn to_cartesian(&self) -> Cartesian<T, S>;
+
+    fn to_keplerian(&self) -> Keplerian<T, S>;
+}
+
 #[derive(Debug, Copy, Clone, PartialEq)]
 pub struct Cartesian<T, S>
 where
@@ -64,12 +74,16 @@ where
     }
 }
 
-impl<T, S> Cartesian<T, S>
+impl<T, S> TwoBody<T, S> for Cartesian<T, S>
 where
     T: PointMass + Copy,
     S: InertialFrame + Copy,
 {
-    pub fn to_keplerian(&self) -> Keplerian<T, S> {
+    fn to_cartesian(&self) -> Cartesian<T, S> {
+        *self
+    }
+
+    fn to_keplerian(&self) -> Keplerian<T, S> {
         Keplerian::from(*self)
     }
 }
@@ -178,10 +192,20 @@ where
     pub fn true_anomaly(&self) -> f64 {
         self.state.true_anomaly()
     }
+}
 
-    pub fn to_cartesian(&self) -> Cartesian<T, S> {
+impl<T, S> TwoBody<T, S> for Keplerian<T, S>
+where
+    T: PointMass + Copy,
+    S: InertialFrame + Copy,
+{
+    fn to_cartesian(&self) -> Cartesian<T, S> {
         Cartesian::from(*self)
     }
+
+    fn to_keplerian(&self) -> Keplerian<T, S> {
+        *self
+    }
 }
 
 impl<T, S> CoordinateSystem for Keplerian<T, S>