Recursion

So first, here's the program whose stack runneth over:

	public class Overflow {
	public static void main(String[] args) {
	foo();
	}
	static void foo() {
	foo();
	}
	}

view raw Overflow.java hosted with ❤ by GitHub

Then we added a counter so we could see how far down the rabbit hole goes:

	public class Counter {
	public static void main(String[] args) {
	foo(0);
	}
	static int foo(int count) {
	count = count + 1;
	System.out.println(count);
	foo(count);
	return count;
	}
	}

view raw Counter.java hosted with ❤ by GitHub

And then limited it so that it wouldn't overflow anymore:

	public class Limited {
	public static void main(String[] args) {
	foo(0);
	}
	static int foo(int count) {
	count = count + 1;
	System.out.println(count);
	if (count == 11000) {
	return count;
	}
	else {
	foo(count);
	}
	return count;
	}
	}

view raw Limited.java hosted with ❤ by GitHub

(Of course in recitation these were all named Foo.java)

And then here's a drawing thingy:

	public class Drawing1 {
	public static void main(String[] args) {
	Turtle.setSpeed(1000);
	y(10);
	}
	static void x(int n) {
	if (n == 0) {
	return;
	}
	else {
	x(n-1);
	Turtle.turn(90);
	y(n-1);
	Turtle.draw(10);
	}
	}
	static void y(int n) {
	if (n == 0) {
	return;
	}
	else {
	Turtle.draw(10);
	x(n-1);
	Turtle.turn(-90);
	y(n-1);
	}
	}
	}

view raw Drawing1.java hosted with ❤ by GitHub

Which uses Turtle.java

And then here's the one that draws the Sierpinski triangle:

	public class Triangle {
	public static void main(String[] args) {
	Turtle.setSpeed(1000);
	x(6);
	}
	static void x(int n) {
	if (n == 0) {
	Turtle.draw(3);
	return;
	}
	else {
	y(n-1);
	Turtle.turn(60);
	x(n-1);
	Turtle.turn(60);
	y(n-1);
	}
	}
	static void y(int n) {
	if (n == 0) {
	Turtle.draw(3);
	return;
	}
	else {
	x(n-1);
	Turtle.turn(-60);
	y(n-1);
	Turtle.turn(-60);
	x(n-1);
	}
	}
	}

view raw Triangle.java hosted with ❤ by GitHub

(Oh yeah and check out this comic. The author says he thought of it while trying to write a program to draw a Sierpinski triangle and he kept getting a StackOverflowError. WHAT WAS HE DOING WRONG?)

There will be no recitation Thanskgiving week. I hope everyone has a wonderful Thanksgiving and I will see you in two weeks.