src/RMCA/Global/Clock.hs

   1 {-# LANGUAGE MultiParamTypeClasses #-}
   2
   3 module RMCA.Global.Clock ( AbsBeat
   4                          , maxAbsBeat
   5                          , metronome
   6                          , tempoToQNoteIvl
   7                          ) where
   8
   9 import FRP.Yampa
  10 import RMCA.Auxiliary
  11 import RMCA.Semantics
  12
  13 -- The absolute beat is the beat number of the global clock, there are
  14 -- 16 starting from 1.
  15 type AbsBeat = BeatNo
  16
  17 maxAbsBeat :: AbsBeat
  18 maxAbsBeat = 16
  19
  20 -- The global system tempo beats every 16th note, each beat is tagged
  21 -- with a beat number modulo sixteen. Each layer is then beating at
  22 -- its own fraction, discarding the unecessary beats.
  23 metronome :: SF Tempo (Event AbsBeat)
  24 metronome = accumBy (\pb _ -> nextBeatNo maxAbsBeat pb) 1 <<<
  25             repeatedlyS () <<^ (15*) <<^ (1/) <<^ fromIntegral
  26
  27 -- Tempo is the number of quarter notes per minute.
  28 tempoToQNoteIvl :: Tempo -> DTime
  29 tempoToQNoteIvl = (15/) . fromIntegral