fromInteger n = (fromInteger n, fromInteger n, fromInteger n)
+-- | Scale a point by a constant.
scale :: Point -> Double -> Point
scale (x, y, z) d = (x*d, y*d, z*d)
+-- | Returns the distance between p1 and p2.
distance :: Point -> Point -> Double
distance p1 p2 =
sqrt $ (x2 - x1)^(2::Int) + (y2 - y1)^(2::Int) + (z2 - z1)^(2::Int)
z2 = z_coord p2
+-- | Returns 'True' if p1 is close to (within 'epsilon' of) p2,
+-- 'False' otherwise.
is_close :: Point -> Point -> Bool
is_close p1 p2 = (distance p1 p2) ~= 0