cancellation happens for instance here: 1 + 1e-50 - 1 == 0
the function again (in the wasteful original form, for clarity). where do you think cancellation may take place? isn't what you call canellation a generic rounding error? ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ normInterval :: [Double] -> Double -> Double -> [Double] normInterval ps lower upper = repair (map (\ x -> (x - oldLower) * stretch + lower) ps) where oldLower = head ps oldUpper = last ps stretch = (upper - lower) / (oldUpper - oldLower) -- fix rounding error: repair [i] = [upper] repair (h:t) = h : repair t ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
(x-oldLower)*a + (oldUpper-x)*b
i got this into my head though. neat. thanks! i will rewrite the function right now. cheers, matthias