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Langton's Ant simulation


Christopher Langton is a co-founder of the research area "artificial live", which deals with the simulation of living creatures. His ant simulation is a perfect example to show that a chaotic system can lead to a well-structured one.

The system follows this algorithm:
An ant is on a white grid and moves upward. As soon as it hits a new cell the following rules apply:

  • if the cell is white, the ant colors it black and rotates 90 degrees to the right
  • if the cell is black, the ant colors it white and rotates 90 degrees to the left

After that, the ant moves to the next cell according to its new direction.

 

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Program code

// Langton.java

import ch.aplu.jgamegrid.*;
import java.awt.Color;

public class Langton extends GameGrid
{
  private final Actor ant = new Actor(true, "sprites/ant.gif");
  private final String title = "JGameGrid - Langton's Ant. # Steps: ";

  public Langton()
  {
    super(100, 100, 6, new Color(240, 240, 240), true);
    setSimulationPeriod(10);
    setBgColor(Color.white);
    addActor(ant, new Location(50, 50), -90);
    reset();
    show();
  }
  
  public void reset()
  {
    getBg().clear();
    setTitle(title + getNbCycles());
  }

  public void act()
  {
    setTitle(title + (getNbCycles() + 1));
    Location loc = ant.getLocation();
    GGBackground bg = getBg();
    Color c = bg.getColor(loc);
    if (c.equals(Color.white))
    {
      bg.fillCell(loc, Color.black, false);
      ant.setDirection(ant.getDirection() + 90);
    }
    else
    {
      bg.fillCell(loc, Color.white, false);
      ant.setDirection(ant.getDirection() - 90);
    }
    ant.move(1);
    if (ant.isNearBorder())
      doPause();
  }

  public static void main(String[] args)
  {
    new Langton();
  }
}