RCMA/Unknown/AvgInt.hs

   1 {-# LANGUAGE Arrows #-}
   2
   3 module AvgInt ( avgInt
   4               ) where
   5
   6 import FRP.Yampa
   7
   8 intNum :: Int
   9 intNum = 3
  10
  11 maxTime :: DTime
  12 maxTime = 10
  13
  14 infinity :: (Fractional a) => a
  15 infinity = 1/0
  16
  17 -- Outputs the average time between intNum of the last events. Goes to
  18 -- infinity if less than intNum events have occured or if no event has
  19 -- occured in maxTime.
  20 avgInt :: SF (Event a) DTime
  21 avgInt = avgInt' [] `switch` ((>>^ fst) . avgInt')
  22   where avgInt' :: [DTime] -> SF (Event a) (DTime, Event [DTime])
  23         avgInt' l = proc e -> do
  24           t <- localTime -< ()
  25           tooLate <- after maxTime [] -< ()
  26           let timeList = (e `tag` (appDTime intNum t l)) `lMerge` tooLate
  27           returnA -< (avgS intNum l, timeList)
  28
  29 appDTime :: Int -> Time -> [DTime] -> [DTime]
  30 appDTime _ _ [] = [0]
  31 appDTime n t l = (t - head l):(take (n-1) l)
  32
  33 avgS :: (Fractional a) => Int -> [a] -> a
  34 avgS n l
  35   | length l /= n = infinity
  36   | otherwise = foldl (+) 0 l / fromIntegral n