getCorePoints   :: ([Double] -> [Double] -> Double) -> [[Double]] -> Double -> Int -> [Int]
getCorePoints dist dataset eps minPts = [ head k | k <- [ (toInteger . head) x | x <- dataset, y <- dataset, dist (tail x) (tai    l y) <= eps], length k >= minPts]

   Couldn't match expected type ‘t0 a0’ with actual type ‘Integer’
    In the first argument of ‘length’, namely ‘k’
    In the first argument of ‘(>=)’, namely ‘length k’