infinite for loop problem

[bluemagica]

package
{
	import flash.geom.*;
	import flash.display.*;
	import flash.events.*;
	
	public class Main extends MovieClip
	{
		var sp:Sprite = new Sprite();
		
		public function Main()
		{	addChild(sp);		
			drawPoints(20,20);
		}
		
		public function drawPoints(sx=0,sy=0)
		{
			var ptArr = [0,0,10,0,10,10,10,20,60,20,60,10,60,0,70,0];
			sp.graphics.lineStyle(1,0x00ff00);
			sp.graphics.moveTo(sx,sy);
			for(var i=2;i<ptArr.length;i+2)  <--PROBLEM PORTION
			{
				sp.graphics.lineTo(ptArr[i]+sx,ptArr[i+1]+sy);
				trace(i);
			}
		}
	}
}

When I run the code, it seems to run eternally and freeze, however in the for loop, if I replace i+2 with i++ and put in another i++ inside, the problem doesn't occur.....any idea what's going on?

[UnknownGuy]

When using i+2, you aren't actually assigning the value (while i++ translates to i = i + 1).

So try instead i += 2 or i = i + 2.

[bluemagica]

oh....thanks....