-- Assume (x,y) \in [0,1)^2.
circles (x,y) = takeWhile (<= 81 % 1) $ sort [distance (x, y) (a, b) | a <- [-10..10], b <- [-10..10]]
circles (x,y) = takeWhile (<= 81 % 1) $ sort [distance (x, y) (a, b) | a <- [-10..10], b <- [-10..10]]
circles (x,y) = takeWhile (<= 81 % 1) $ sort [distance (x, y) (a, b) | a <- [-10..10], b <- [-10..10]]