data Region = UnitCircle | Scale Float Region | Union Region Region

example = Union (Scale 2.0 UnitCircle) UnitCircle

interp :: Region -> ((Float,Float) -> Bool)
interp UnitCircle (x,y) = x*x+y*y <= 1
interp (Scale s r) (x,y) = interp r (x*s,y*s)
interp (Union r1 r2) p = interp r1 p || interp r2 p