From 3f107ae90b229e3f382989996d77f54faed4d8f0 Mon Sep 17 00:00:00 2001
From: Peter Wu <lekensteyn@gmail.com>
Date: Thu, 9 Jan 2014 18:05:08 +0100
Subject: Fix confusion of meters, time pos and GST

Robots get a speed of 19 km/s (average human speed).
---
 src/Robot.java     | 40 +++++++++++++++++++++++++++++++++-------
 src/RobotRace.java |  4 ++--
 2 files changed, 35 insertions(+), 9 deletions(-)

diff --git a/src/Robot.java b/src/Robot.java
index 0e496e1..3b9c0cb 100644
--- a/src/Robot.java
+++ b/src/Robot.java
@@ -48,15 +48,20 @@ class Robot extends BetterBase {
     private double speed;
 
     /**
-     * Location of the robot on the track (in terms of GlobalState time).
+     * Location of the robot on the track (in meters).
      */
-    private double robot_time_pos;
+    private double robot_pos_meters;
 
     /**
      * The lane number on which this robot is positioned. Must be a positive
      * number greater or equal to zero.
      */
     private final int laneNo;
+    /**
+     * Length of the race track in meters. (76 is the approximate perimeter of
+     * an ellipse with half-widths 10 and 14.)
+     */
+    private final static double TRACK_LENGTH = 76.0;
 
     /**
      * Constructs the robot with initial parameters.
@@ -479,10 +484,31 @@ class Robot extends BetterBase {
 
     /**
      * Determine the location of the robot on the track.
-     * @return A positive number (time).
+     * @return A positive number between 0 (begin) and 1 (end). Higher values
+     * can also be returned which means that at least one full round has been
+     * made.
      */
     public double getTimePos() {
-        return robot_time_pos;
+        double pos = meter2racepos(robot_pos_meters);
+        return pos;
+    }
+
+    /**
+     * Map meters to the position on the race track.
+     * @param meter Distance in meters.
+     * @return Position on the race track.
+     */
+    public static double meter2racepos(double meter) {
+        return meter / TRACK_LENGTH;
+    }
+
+    /**
+     * Map the position on the race track to meters.
+     * @param gst Elapsed global state time.
+     * @return Distance in meters.
+     */
+    public static double racepost2meter(double gst) {
+        return gst * TRACK_LENGTH;
     }
 
     /**
@@ -494,7 +520,7 @@ class Robot extends BetterBase {
     }
 
     /**
-     * Gets the speed of this robot.
+     * Gets the speed of this robot (in meters per second).
      */
     public double getSpeed() {
         return speed;
@@ -505,14 +531,14 @@ class Robot extends BetterBase {
      */
     public void walkSome(double seconds) {
         assert seconds >= 0 : "Robot cannot walk backwards!";
-        robot_time_pos += speed * seconds;
+        robot_pos_meters += speed * seconds;
     }
 
     /**
      * Resets the position on the track to the begin.
      */
     public void resetPosition() {
-        robot_time_pos = 0;
+        robot_pos_meters = 0;
     }
 
     /**
diff --git a/src/RobotRace.java b/src/RobotRace.java
index ee1fc86..3c2f9cd 100644
--- a/src/RobotRace.java
+++ b/src/RobotRace.java
@@ -132,9 +132,9 @@ public class RobotRace extends Base {
     private final static double SPEED_RECALC_INTERVAL = .500;
 
     /**
-     * Desired average robot speed in meter per second.
+     * Desired average robot speed in meter per second. (Ne3 / 3600 is N km/h)
      */
-    private final static double TARGET_ROBOT_SPEED = .03;
+    private final static double TARGET_ROBOT_SPEED = 19e3 / 3600;
 
     /**
      * Used for randomizing robot speed.
-- 
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