> Nearly anything works without thinking too much about the types, but I
> don't like the use of fromInteger in the average and main functions. Is it
> possible that the integers are automaticly converted to floats?

I recommend using Float or Double instead of Int for your point coordinates. You'll eliminate the need to convert to Float/Double. More importantly, your whole model will then be resolution independent, supporting continuous scaling, sub-pixel translation, rotation, etc. See http://conal.net/Pan for examples & papers.

Cheers, - Conal