Wall avoidance

Fragment of a discussion from Talk:Talon/source
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package cs;

import java.awt.geom.Point2D;
import robocode.AdvancedRobot;
import robocode.ScannedRobotEvent;
import robocode.util.Utils;
 
/**
 * Talon - a Nano Melee robot by Chase
 * 
 * The idea is to avoid driving toward enemy robots, nearer ones are more
 * dangerous to drive towards.
 * 
 * Codesize: 248
 */
public class Talon extends AdvancedRobot {
	private static Point2D.Double[] map = new Point2D.Double[10];
	private static int n;
 
	public void run() {
		//setAdjustGunForRobotTurn(true); //Sheldor: In melee this doesn't really matter.
		//setAllColors(Color.RED); //Sheldor: I'm very sorry. :(
		double angle, bestDanger, danger;
		while(true) {
		
			setAhead((bestDanger = angle = 360) - (5 * getTurnRemaining())); //Sheldor: Slowing down before making big turns makes the wall avoidance much better.
			
			while(angle-- > 0) {
				int t;
				setFire(t = getOthers()); //Sheldor: From Graviton.
				
				//Sheldor: Drive toward the center of the field when the bot gets near a wall.
				//This will only work properly on a 1000/1000 pixel field.
				danger = -Math.abs(Utils.normalRelativeAngleDegrees(angle - Math.toDegrees(Math.atan2(getX() - 500, getY() - 500)))) *
					(table.charAt((int)getX()) + table.charAt((int)getY()));
					
				try {
					while(true) {
						// our most recent scans, unfortunately not enough room
						// to project them
						Point2D.Double v;
						// set our gun to face this nearest enemy
						setTurnGunRight(Utils.normalRelativeAngleDegrees((v = map[--t]).y - getGunHeading()));
						// the difference between current angle we are
						// considering and the enemy
						// multiply it by how close they are, closer is more
						// dangerous to move towards
						danger += 1 / (Math.abs(Utils.normalRelativeAngleDegrees(angle - v.y))) / v.x; //Sheldor: "X / Y" has exactly the same effect as "X * (1 / Y)" but is ~3 bytes smaller.  
					}
				} catch(Exception e) {
					// We don't have room for any kind of sanity checks, also
					// the only way to get out of the loop without
					// having to have a comparison, saves us some code size
				}
				if(danger < bestDanger) {
					bestDanger = danger;
					setTurnRight(Utils.normalRelativeAngleDegrees(angle - getHeading()));
				}
			}
			// Turning it by only 1 saves us some code size but in radians this
			// value > PI/4 the maximum
			// turn the radar can turn, meaning it will cover the full arc as
			// long as we call it every turn.
			turnRadarRightRadians(1);
		}
	}
 
	public void onScannedRobot(ScannedRobotEvent e) {
		try {
			// Set the most recent scan into our map of enemies
			map[--n] = new Point2D.Double(e.getDistance(), getHeading() + e.getBearing());
		}
		catch(Exception ex) {
			// attempted to scan but it failed, set the number of enemies again
			// we miss an enemy scan but we gain some code size here
			n = getOthers();
		}
	}
	
	static final String table = "\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064" +
			"\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0001" +
			"\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001" +
			"\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0" +
			"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0" +
			"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0" +
			"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0" +
			"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0" +
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			"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0" +
			"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0" +
			"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0" +
			"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0" +
			"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\u0001\u0001\u0001\u0001\u0001" +
			"\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001" +
			"\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0001\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064" +
			"\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064" +
			"\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064\u0064";
}
Sheldor18:10, 22 February 2013