RMCA/Translator/Filter.hs

   1 -- Contains function for scheduling and filtering events given the
   2 -- correct informations.
   3
   4 module RMCA.Translator.Filter where
   5
   6 import Data.Bifunctor          as BF
   7 import Data.Function           (on)
   8 import Data.List               (group, groupBy, sortBy)
   9 import Data.Ord
  10 import FRP.Yampa
  11 import RMCA.Semantics
  12 import RMCA.Translator.Message
  13 import Sound.JACK              (NFrames (NFrames))
  14
  15 -- Takes a list of time stamped "things", a sample rate and a buffer
  16 -- size. The function argument is a function that needs to tell which
  17 -- arguments are kept in the case where two would come into
  18 -- contact. On the left are the events that can be thrown into the
  19 -- buffer, on the right are the events that will need to wait. Both
  20 -- list are sorted.
  21 --
  22 -- /!\ The frame number is relative. A preprocessing operation
  23 -- removing all events too soon to be happening and shifting them is
  24 -- necessary.
  25 schedule :: Frames
  26          -> [(Frames, a)]
  27          -> ([(Frames,a)], [(Frames,a)])
  28 schedule size = BF.first scatterEvents
  29                 . break ((>= size) . fst) . sortBy (comparing fst)
  30
  31 {- Rendered useless
  32 -- The function choose between the event in case two are in conflict.
  33 --
  34 -- /!\ That functional argument is a bit unsatisfying, it would be
  35 -- probably better if we'd try to push events to the next frame if
  36 -- they conflict and only remove them if it's impossible to do
  37 -- otherwise.
  38 nubDuplicate :: (Eq a) => ([a] -> a) -> [(Frames, a)] -> [(Frames, a)]
  39 nubDuplicate f = map (BF.second f) . scatterEvents
  40                  . map (\l@((n,_):_) -> (n,map snd l)) . group
  41 -}
  42 -- When to events are at the same frame, shift them so that they are
  43 -- all separated by one frame. Then take every list and make sure that
  44 -- the first frame of the next list is at least one frame after the
  45 -- last frame of that list.
  46 scatterEvents :: [(Frames, a)] -> [(Frames, a)]
  47 scatterEvents (x@(n,a):(m,b):xs) = x:scatterEvents ((m',b):xs)
  48   where m' = m + max 0 (1 + n - m)
  49 scatterEvents [x] = [x]
  50 scatterEvents _ = []