data Interval = Interval Double Double

type Step = Double

input :: ( [ (Double -> Double) ], [Double], Interval, Step)
input = ( [f1, f2], [f1_, f2_], interval, step)
        where
            f1 x = (30 + 5 * x**2) / (24 - 2*x)
            f2 = (40 -) . (7 *) 
            interval = Interval 1 6
            f1_ = 2.5
            f2_ = 22
            step = 0.001

argsteps :: Interval -> Step -> [Double]
argsteps (Interval left right) step 
    | abs left > right = []
    | otherwise = left : argsteps (Interval (left + step) right) step
 
maxmin = mm maximum minimum
minmax = mm minimum maximum

mm :: ([(Double, Double)] -> (Double, Double)) -> ([Double] -> Double) -> [(Double->Double)] -> [Double] -> Interval -> Step -> (Double, Double)
mm f1 f2 funcs fs_ interval step = f1 [ (f x, x)  | x <- args ]
    where args = argsteps interval step
          f x  = f2 [func x / func_ | (func, func_) <- zip funcs fs_]

do_stuff = [f funcs fs_ interval step | f <- [maxmin, minmax]]
    where (funcs, fs_, interval, step) = input