src/RMCA/Auxiliary/Yampa.hs

   1 {-# LANGUAGE Arrows #-}
   2
   3 module RMCA.Auxiliary.Yampa where
   4
   5 import FRP.Yampa
   6 import Data.Maybe
   7 import RMCA.Auxiliary.Misc
   8
   9 import Debug.Trace
  10
  11 -- | = Yampa
  12
  13 countTo :: (Integral b) => b -> SF (Event a) (Event b)
  14 countTo n = count >>^ filterE (== n)
  15
  16 -- | Synchonizes two event sources. An event on the first source will be delayed until an event occurs on the second.
  17 --
  18 -- Ex:
  19 -- Event a => . . 1 . . . . 2 . . . 3 . . 4 . . . . . 5 . . 6 . . . . .
  20 -- Event b => . a . . . b . . . c . . . . . . d . e . f . . . . . g . .
  21 -- wairFor => . . . . . 1 . . . 2 . . . . . . 4 . . . 5 . . . . . 6 . .
  22
  23 waitForEvent :: (Show a, Show b) => SF (Event a, Event b) (Event a)
  24 waitForEvent = proc (ea,eb) -> do
  25   em <- arr $ uncurry $ mapMerge Left Right (\_ b -> Right b) -< let a = (ea,eb) in traceShow a a
  26   hob <- dAccumHoldBy accumulator NoEvent -< em
  27   returnA -< let a = eb *> (ea `lMerge` hob) in traceShow (a,eb) a
  28   where accumulator :: Event a -> Either a b -> Event a
  29         accumulator _ (Left a) = Event a
  30         accumulator _ (Right _) = NoEvent
  31         --accumulator _ (Right b) =
  32
  33 {-
  34 waitForEvent :: SF (Event b, Event a) (Event b)
  35 waitForEvent = proc (eb,ea) -> do
  36   rec
  37     es' <- iPre NoEvent -< es
  38     es <- rSwitch waitAux -< ((eb,ea),es' `tag` waitAux)
  39   returnA -< es
  40   where waitAux = proc (eb,ea) -> do
  41           --ea' <- (if b then notYet else identity) -< ea
  42           eb' <- accumHoldBy (\_ b -> Event b) NoEvent -< eb
  43           returnA -< ea *> eb'
  44 -}
  45 -- | 'stepBack' contains its previous argument as its output. Because it's hard to define it at time 0, it's wrapped up in a 'Maybe'.
  46 stepBack :: SF a (Maybe a)
  47 stepBack = sscan f (Nothing, Nothing) >>^ snd
  48   where f :: (Maybe a, Maybe a) -> a -> (Maybe a, Maybe a)
  49         f (Nothing,_) x' = (Just x', Nothing)
  50         f (Just x, _) x' = (Just x', Just x)
  51
  52 -- | Like 'stepBack' but the output value is always defined and is equal to the input at time 0.
  53 stepBack' :: SF a a
  54 stepBack' = proc x -> do
  55   x' <- stepBack -< x
  56   returnA -< fromMaybe x x'
  57
  58 -- | Throws an 'Event' when the incoming signal change. The 'Event' is tagged with the new value.
  59 onChange :: (Eq a) => SF a (Event a)
  60 onChange = proc x -> do
  61   x' <- stepBack -< x
  62   let makeEvent x x'
  63         | isNothing x' = NoEvent
  64         | otherwise = let x'' = fromJust x' in
  65             if x'' == x then NoEvent else Event x
  66   returnA -< makeEvent x x'
  67
  68 -- | Similar to 'onChange' but contains its initial value in the first
  69 -- event.
  70 onChange' :: (Eq a) => SF a (Event a)
  71 onChange' = proc x -> do
  72   x' <- stepBack -< x
  73   -- If it's the first value, throw an Event, else behave like onChange.
  74   let makeEvent x x'
  75         | isNothing x' = Event x
  76         | otherwise = let x'' = fromJust x' in
  77             if x'' == x then NoEvent else Event x
  78   returnA -< makeEvent x x'
  79
  80 -- | Integrates some variable modulo something.
  81 integralMod :: (Real a, VectorSpace a s) => a -> SF a a
  82 integralMod x = intMod' 0
  83   where intMod' x0 = switch (intMod'' x0) (\y -> intMod' (y - x))
  84         intMod'' x0 =  proc t -> do
  85           it <- (+ x0) ^<< integral -< t
  86           es <- edgeBy (\_ y -> maybeIf (y > x) $> y) 0 -< it
  87           returnA -< (it,es)
  88
  89
  90
  91 -- | Generates a sine function whose period is given as a varying input.
  92 varFreqSine :: SF DTime Double
  93 varFreqSine = sin ^<< (2*pi*) ^<< integralMod 1 <<^ (1/)
  94
  95 -- | Generates an 'Event' with a regular period, which is given as an input to the signal function.
  96 repeatedlyS :: a -> SF DTime (Event a)
  97 repeatedlyS x = edgeBy (\a b -> maybeIf (a * b < 0) $> x) 0
  98                 <<< varFreqSine <<^ (2*)
  99
 100 repeatedlyS' :: a -> SF DTime (Event a)
 101 repeatedlyS' x = (repeatedlyS x &&& now x) >>> arr (uncurry lMerge)
 102
 103 -- |
 104 -- = Curry and uncurry functions