findRoot.hs

findRoot :: Float -> Float -> Float
findRoot digit n = find n candidate
    where scale = 10 ** digit
          candidate = map (/ scale) [1..(n * scale)]

find :: Float -> [Float] -> Float
find _ [x] = x
find n xs | (target ** 2) >= n = find n smaller
          | otherwise          = find n bigger
          where mid              = (length xs) `div` 2
                (smaller,bigger) = splitAt mid xs
                target           = last smaller