fn main() -> i32
{
	var x: i32 = 27;
	var y = determine_collatz_number(x);
	return: y
}

// Calculate the number of Collatz steps needed to reach 1.
// The Collatz conjecture states that this function always terminates.
fn determine_collatz_number(start: i32) -> i32
{
	var x = start;
	var steps = 0;
	{
		if x == 1
			goto return;
		do_collatz_step(&x);
		steps = steps + 1;
		loop;
	}

	return: steps
}

// If x is even, divide it by 2. Otherwise calculate 3 * x + 1.
// Do this without division or modulo operators (for demonstrative purposes).
fn do_collatz_step(x: &i32)
{
	var y = x;
	{
		if y == 0
		{
			if y + y == x
			{
				x = y;
				goto end;
			}
			y = y + 1;
			loop;
		}
		else if y == 1
		{
			x = 3 * x + 1;
			goto end;
		}
		y = y - 2;
		loop;
	}
	end:
}