Reactogon/Translator/Filter.hs

   1 -- Contains function for scheduling and filtering events given the
   2 -- correct informations.
   3
   4 module Reactogon.Translator.Filter where
   5
   6 import Data.Bifunctor               as BF
   7 import Data.List                    (group, sortBy)
   8 import Data.Ord
   9 import FRP.Yampa
  10 import Reactogon.Semantics
  11 import Reactogon.Translator.Message
  12 import Sound.JACK                   (NFrames (NFrames))
  13
  14 -- Takes a list of time stamped "things", a sample rate and a buffer
  15 -- size. The function argument is a function that needs to tell which
  16 -- arguments are kept in the case where two would come into
  17 -- contact. On the left are the events that can be thrown into the
  18 -- buffer, on the right are the events that will need to wait. Both
  19 -- list are sorted.
  20 --
  21 -- /!\ The time is relative. A preprocessing operation removing all
  22 -- events too soon to be happening and shifting them is necessary.
  23 schedule :: (Eq a) =>
  24             SampleRate
  25          -> NFrames
  26          -> [(Time, a)]
  27          -> ([(NFrames,a)], [(Time,a)])
  28 schedule sr (NFrames size) = BF.first convertTime . break ((>= maxTime) . fst)
  29                              . sortBy (comparing fst)
  30   where srd = fromIntegral sr
  31         maxTime = fromIntegral size / srd
  32         convertTime :: (Eq a) => [(Time, a)] -> [(NFrames, a)]
  33         convertTime = map (BF.first (NFrames . floor . (srd *)))
  34
  35 -- The function choose between the event in case two are in conflict.
  36 --
  37 -- /!\ That functional argument is a bit unsatisfying, it would be
  38 -- probably better if we'd try to push events to the next frame if
  39 -- they conflict and only remove them if it's impossible to do
  40 -- otherwise.
  41 nubDuplicate :: (Eq a) => ([a] -> a) -> [(NFrames, a)] -> [(NFrames, a)]
  42 nubDuplicate f = map (BF.second f)
  43                  . map (\l@((n,_):_) -> (n,map snd l)) . group
  44
  45 chooseDuplicate :: [a] -> a
  46 chooseDuplicate = undefined