anchor.diff:    
     public void accelerate();
   }
  ----
  +----
   
   Here is an example of a class implementing this interface.
   
  ----
  +----
   public class FastRobot {
     private int currentSpeed;
     
  
positive.code:     currentSpeed *= 2;
    }
  }
  
  
negative.code: 
  The following example indicates that anything that satisfies the `Robot` interface can be moved, can give its current position (as an integer), and can accelerate. But it does not say how any of this is done, internally.
  
  ----
  public interface Robot {
    public void move(int steps);
    
  