[Haskell-cafe] performance issue and HGL

Hello, I've created a simple Mandelbrot set generator, using HGL, the source is viewable at: http://pastebin.dqd.cz/cUmg/ 1. The problem is, that it is very slow. It is obvious that what takes the most time is the "mandel" function computation. I have no idea, how it can be improved. 2. What is the easiest way of changing a color and plotting a pixel with it? Do I always have to "create a pen" for it? Isn't there a simple way? Already – using a line to plot a pixel is probably not the best way… Thanks