lessThanTenBuiltin :: [Double] -> [Double]
lessThanTenBuiltin = filter (< 10)

lessThanTenRecursive :: [Double] -> [Double]
lessThanTenRecursive [] = []
lessThanTenRecursive (x:xs)
    | x < 10    = x : lessThanTenRecursive xs
    | otherwise = lessThanTenRecursive xs