import tester.*;

interface IAnimal {
	IAnimal feed(double n);
}

class Snake implements IAnimal {
	String name;
	double weight;
	String food;
	Snake(String name, double weight, String food) {
		this.name = name;
		this.weight = weight;
		this.food = food;
	}
	
	// To check whether this snake is lighter than
	// n pounds
	boolean isLighter(double n) {
		return this.weight < n;
	}
	
	// To feed the snake amt pounds of food
	public IAnimal feed(double amt) {
		return new Snake(this.name,
				         this.weight + amt,
				         this.food);
	}
}

class Dillo implements IAnimal {
	double weight;
	boolean isAlive;
	Dillo(double weight, boolean isAlive) {
		this.weight = weight;
		this.isAlive = isAlive;
	}
	
	public IAnimal feed(double n) {
		if (this.weight >= 10)
			return this;
		else if (this.isAlive)
			return new Dillo(this.weight + n, true);
		else
		    return this;
	}
}

class Posn {
	int x;
	int y;
	Posn(int x, int y) {
		this.x = x;
		this.y = y;
	}
}

class Ant implements IAnimal {
	double weight;
	Posn location;
	Ant(double weight, Posn location) {
		this.weight = weight;
		this.location = location;
	}
	
	public IAnimal feed(double n) {
		return new Ant(this.weight + n,
		        this.location);
	}
}

interface IGrade {
}

class NoGrade implements IGrade {
	NoGrade() { }
}

class NumberGrade implements IGrade {
	int grade;
	NumberGrade(int grade) {
		this.grade = grade;
	}
}

class Examples{
  	Dillo rolly = new Dillo(2, true);
  	Ant suzy = new Ant(0.0001, new Posn(3, 4));
  	Snake fred = new Snake("Fred", 10, "cereal");
  	IAnimal friend = suzy;
  	// Ant yourFriend = friend;  //-- not ok
  	IGrade g1 = new NoGrade();
  	IGrade g2 = new NumberGrade(100);
  	
  	void tests(Tester t) {
  		t.checkExpect(new Snake("Slinky", 12, "grass").isLighter(10), false);
  		t.checkExpect(fred.isLighter(13), true);
  		
  		t.checkExpect(new Snake("Slinky", 12, "grass").feed(2),
  				      new Snake("Slinky", 14, "grass"));
  		t.checkExpect(fred.feed(3), new Snake("Fred", 13, "cereal"));
  		t.checkExpect(rolly.feed(1), new Dillo(3, true));
  		t.checkExpect(new Dillo(3, false).feed(1), new Dillo(3, false));
  		t.checkExpect(new Dillo(13, true).feed(1), new Dillo(13, true));
  		t.checkExpect(friend.feed(0.002), new Ant(0.0021, new Posn(3, 4)));
  	}
}