From 46afb6bf501f4001c4bdb7bd2f2db7c466f95554 Mon Sep 17 00:00:00 2001
From: Juan Marin Noguera <juan@mnpi.eu>
Date: Tue, 25 Jul 2023 18:22:04 +0200
Subject: Solvned project from 2020

Note that Go didn't have generics back then.
---
 examples/arenstorf.go | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)
 create mode 100644 examples/arenstorf.go

(limited to 'examples/arenstorf.go')

diff --git a/examples/arenstorf.go b/examples/arenstorf.go
new file mode 100644
index 0000000..6506a6a
--- /dev/null
+++ b/examples/arenstorf.go
@@ -0,0 +1,74 @@
+// Example visualization of the Arenstorf orbit.
+//
+// Copyright (C) 2020 Juan Marín Noguera
+//
+// This file is part of Solvned.
+//
+// Solvned is free software: you can redistribute it and/or modify it under the
+// terms of the GNU Lesser General Public License as published by the Free
+// Software Foundation, either version 3 of the License, or (at your option) any 
+// later version.
+//
+// Solvned is distributed in the hope that it will be useful, but WITHOUT ANY 
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+// A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
+// details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with Solvned. If not, see <https://www.gnu.org/licenses/>.
+
+package main
+
+import (
+	"fmt"
+	"github.com/Arafatk/glot"
+	"github.com/JwanMan/mned"
+	"github.com/JwanMan/mned/ivp"
+	"github.com/JwanMan/mned/method"
+	"os"
+)
+
+func main() {
+	var backed bool = false
+	problem := ivp.ArenstorfOrbit()
+	solution := mned.CacheSolve(
+		method.RKFehlberg(0.01, 0.01, 1e-7, 0.1),
+		&problem,
+		mned.HermiteForIVP(&problem),
+		mned.Event{
+			Cross: func(p *mned.Point) float64 {
+				return p.Value[1]
+			},
+			Tolerance: 0.01,
+			Action: func(p *mned.Point) bool {
+				if p.Value[0] < 0 {
+					backed = true
+				}
+				return true
+			},
+		},
+		mned.Event{
+			Cross: func(p *mned.Point) float64 {
+				return p.Value[1]
+			},
+			Tolerance: 0.01,
+			Action: func(p *mned.Point) bool {
+				return p.Value[0] <= 0.9 || !backed
+			},
+		},
+	)
+	solution.StepToEnd()
+	coords := solution.PointCoords()
+	fmt.Printf("Took %v steps.\n", len(coords[0]))
+	plot, err := glot.NewPlot(2, true, false)
+	if err != nil {
+		fmt.Printf("Couldn't create plot: %v\n", err)
+		os.Exit(1)
+	}
+	if err := plot.AddPointGroup("Orbit", "lines", [][]float64{
+		coords[1], coords[2],
+	}); err != nil {
+		fmt.Printf("Couldn't draw the points: %v\n", err)
+		os.Exit(1)
+	}
+}
-- 
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