-- |
-- Copyright  : (c) Ivan Perez, 2019-2022
--              (c) Ivan Perez and Manuel Baerenz, 2016-2018
-- License    : BSD3
-- Maintainer : ivan.perez@keera.co.uk
--
-- Event Signal Functions and SF combinators.
--
-- Events represent values that only exist instantaneously, at discrete points
-- in time. Examples include mouse clicks, zero-crosses of monotonic continuous
-- signals, and square waves.
--
-- For signals that carry events, there should be a limit in the number of
-- events we can observe in a time period, no matter how much we increase the
-- sampling frequency.
module FRP.BearRiver.EventS
    (
      -- * Basic event sources
      never
    , now
    , after
    , repeatedly
    , afterEach
    , afterEachCat
    , delayEvent
    , delayEventCat
    , edge
    , iEdge
    , edgeTag
    , edgeJust
    , edgeBy

      -- * Stateful event suppression
    , notYet
    , once
    , takeEvents
    , dropEvents

      -- * Hybrid SF combinators
    , snap
    , snapAfter
    , sample
    , sampleWindow

      -- * Repetition and switching
    , recur
    , andThen
    )
  where

-- External imports
import Control.Arrow (arr, (&&&), (>>>), (>>^))

-- Internal imports (dunai)
import Control.Monad.Trans.MSF                 (ask)
import Data.MonadicStreamFunction              (feedback)
import Data.MonadicStreamFunction.InternalCore (MSF (MSF))

-- Internal imports
import FRP.BearRiver.Arrow        (dup)
import FRP.BearRiver.Basic        (constant, identity, (-->), (>--))
import FRP.BearRiver.Event        (Event (..), maybeToEvent, tag)
import FRP.BearRiver.Hybrid       (accumBy)
import FRP.BearRiver.InternalCore (SF, Time)
import FRP.BearRiver.Switches     (dSwitch, switch)

-- | Event source that never occurs.
never :: Monad m => SF m a (Event b)
never :: forall (m :: * -> *) a b. Monad m => SF m a (Event b)
never = Event b -> SF m a (Event b)
forall (m :: * -> *) b a. Monad m => b -> SF m a b
constant Event b
forall a. Event a
NoEvent

-- | Event source with a single occurrence at time 0. The value of the event is
-- given by the function argument.
now :: Monad m => b -> SF m a (Event b)
now :: forall (m :: * -> *) b a. Monad m => b -> SF m a (Event b)
now b
b0 = b -> Event b
forall a. a -> Event a
Event b
b0 Event b -> SF m a (Event b) -> SF m a (Event b)
forall (m :: * -> *) b a. Monad m => b -> SF m a b -> SF m a b
--> SF m a (Event b)
forall (m :: * -> *) a b. Monad m => SF m a (Event b)
never

-- | Event source with a single occurrence at or as soon after (local) time /q/
-- as possible.
after :: Monad m
      => Time -- ^ The time /q/ after which the event should be produced
      -> b    -- ^ Value to produce at that time
      -> SF m a (Event b)
after :: forall (m :: * -> *) b a. Monad m => Time -> b -> SF m a (Event b)
after Time
q b
x = Time
-> MSF (ClockInfo m) (a, Time) (Event b, Time)
-> MSF (ClockInfo m) a (Event b)
forall (m :: * -> *) c a b.
Monad m =>
c -> MSF m (a, c) (b, c) -> MSF m a b
feedback Time
q MSF (ClockInfo m) (a, Time) (Event b, Time)
forall {a}. MSF (ClockInfo m) (a, Time) (Event b, Time)
go
  where
    go :: MSF (ClockInfo m) (a, Time) (Event b, Time)
go = ((a, Time)
 -> ReaderT
      Time
      m
      ((Event b, Time), MSF (ClockInfo m) (a, Time) (Event b, Time)))
-> MSF (ClockInfo m) (a, Time) (Event b, Time)
forall (m :: * -> *) a b. (a -> m (b, MSF m a b)) -> MSF m a b
MSF (((a, Time)
  -> ReaderT
       Time
       m
       ((Event b, Time), MSF (ClockInfo m) (a, Time) (Event b, Time)))
 -> MSF (ClockInfo m) (a, Time) (Event b, Time))
-> ((a, Time)
    -> ReaderT
         Time
         m
         ((Event b, Time), MSF (ClockInfo m) (a, Time) (Event b, Time)))
-> MSF (ClockInfo m) (a, Time) (Event b, Time)
forall a b. (a -> b) -> a -> b
$ \(a
_, Time
t) -> do
           Time
dt <- ReaderT Time m Time
forall (m :: * -> *) r. Monad m => ReaderT r m r
ask
           let t' :: Time
t' = Time
t Time -> Time -> Time
forall a. Num a => a -> a -> a
- Time
dt
               e :: Event b
e  = if Time
t Time -> Time -> Bool
forall a. Ord a => a -> a -> Bool
> Time
0 Bool -> Bool -> Bool
&& Time
t' Time -> Time -> Bool
forall a. Ord a => a -> a -> Bool
< Time
0 then b -> Event b
forall a. a -> Event a
Event b
x else Event b
forall a. Event a
NoEvent
               ct :: MSF (ClockInfo m) (a, Time) (Event b, Time)
ct = if Time
t' Time -> Time -> Bool
forall a. Ord a => a -> a -> Bool
< Time
0 then (Event b, Time) -> MSF (ClockInfo m) (a, Time) (Event b, Time)
forall (m :: * -> *) b a. Monad m => b -> SF m a b
constant (Event b
forall a. Event a
NoEvent, Time
t') else MSF (ClockInfo m) (a, Time) (Event b, Time)
go
           ((Event b, Time), MSF (ClockInfo m) (a, Time) (Event b, Time))
-> ReaderT
     Time
     m
     ((Event b, Time), MSF (ClockInfo m) (a, Time) (Event b, Time))
forall a. a -> ReaderT Time m a
forall (m :: * -> *) a. Monad m => a -> m a
return ((Event b
e, Time
t'), MSF (ClockInfo m) (a, Time) (Event b, Time)
ct)

-- | Event source with repeated occurrences with interval q.
--
-- Note: If the interval is too short w.r.t. the sampling intervals, the result
-- will be that events occur at every sample. However, no more than one event
-- results from any sampling interval, thus avoiding an "event backlog" should
-- sampling become more frequent at some later point in time.
repeatedly :: Monad m => Time -> b -> SF m a (Event b)
repeatedly :: forall (m :: * -> *) b a. Monad m => Time -> b -> SF m a (Event b)
repeatedly Time
q b
x
    | Time
q Time -> Time -> Bool
forall a. Ord a => a -> a -> Bool
> Time
0     = [(Time, b)] -> SF m a (Event b)
forall (m :: * -> *) b a.
Monad m =>
[(Time, b)] -> SF m a (Event b)
afterEach [(Time, b)]
qxs
    | Bool
otherwise = [Char] -> SF m a (Event b)
forall a. HasCallStack => [Char] -> a
error [Char]
"bearriver: repeatedly: Non-positive period."
  where
    qxs :: [(Time, b)]
qxs = (Time
q, b
x)(Time, b) -> [(Time, b)] -> [(Time, b)]
forall a. a -> [a] -> [a]
:[(Time, b)]
qxs

-- | Event source with consecutive occurrences at the given intervals. Should
-- more than one event be scheduled to occur in any sampling interval, only the
-- first will in fact occur to avoid an event backlog.
afterEach :: Monad m => [(Time, b)] -> SF m a (Event b)
afterEach :: forall (m :: * -> *) b a.
Monad m =>
[(Time, b)] -> SF m a (Event b)
afterEach [(Time, b)]
qxs = [(Time, b)] -> SF m a (Event [b])
forall (m :: * -> *) b a.
Monad m =>
[(Time, b)] -> SF m a (Event [b])
afterEachCat [(Time, b)]
qxs SF m a (Event [b])
-> MSF (ClockInfo m) (Event [b]) (Event b)
-> MSF (ClockInfo m) a (Event b)
forall {k} (cat :: k -> k -> *) (a :: k) (b :: k) (c :: k).
Category cat =>
cat a b -> cat b c -> cat a c
>>> (Event [b] -> Event b) -> MSF (ClockInfo m) (Event [b]) (Event b)
forall b c. (b -> c) -> MSF (ClockInfo m) b c
forall (a :: * -> * -> *) b c. Arrow a => (b -> c) -> a b c
arr (([b] -> b) -> Event [b] -> Event b
forall a b. (a -> b) -> Event a -> Event b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap [b] -> b
forall a. HasCallStack => [a] -> a
head)

-- | Event source with consecutive occurrences at the given intervals. Should
-- more than one event be scheduled to occur in any sampling interval, the
-- output list will contain all events produced during that interval.
afterEachCat :: Monad m => [(Time, b)] -> SF m a (Event [b])
afterEachCat :: forall (m :: * -> *) b a.
Monad m =>
[(Time, b)] -> SF m a (Event [b])
afterEachCat = Time -> [(Time, b)] -> SF m a (Event [b])
forall (m :: * -> *) b a.
Monad m =>
Time -> [(Time, b)] -> SF m a (Event [b])
afterEachCat' Time
0
  where
    afterEachCat' :: Monad m => Time -> [(Time, b)] -> SF m a (Event [b])
    afterEachCat' :: forall (m :: * -> *) b a.
Monad m =>
Time -> [(Time, b)] -> SF m a (Event [b])
afterEachCat' Time
_ []  = SF m a (Event [b])
forall (m :: * -> *) a b. Monad m => SF m a (Event b)
never
    afterEachCat' Time
t [(Time, b)]
qxs = (a -> ClockInfo m (Event [b], SF m a (Event [b])))
-> SF m a (Event [b])
forall (m :: * -> *) a b. (a -> m (b, MSF m a b)) -> MSF m a b
MSF ((a -> ClockInfo m (Event [b], SF m a (Event [b])))
 -> SF m a (Event [b]))
-> (a -> ClockInfo m (Event [b], SF m a (Event [b])))
-> SF m a (Event [b])
forall a b. (a -> b) -> a -> b
$ \a
_ -> do
      Time
dt <- ReaderT Time m Time
forall (m :: * -> *) r. Monad m => ReaderT r m r
ask
      let ([b]
ev, Time
t', [(Time, b)]
qxs') = [b] -> Time -> [(Time, b)] -> ([b], Time, [(Time, b)])
forall b. [b] -> Time -> [(Time, b)] -> ([b], Time, [(Time, b)])
fireEvents [] (Time
t Time -> Time -> Time
forall a. Num a => a -> a -> a
+ Time
dt) [(Time, b)]
qxs
          ev' :: Event [b]
ev' = if [b] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [b]
ev
                  then Event [b]
forall a. Event a
NoEvent
                  else [b] -> Event [b]
forall a. a -> Event a
Event ([b] -> [b]
forall a. [a] -> [a]
reverse [b]
ev)

      (Event [b], SF m a (Event [b]))
-> ClockInfo m (Event [b], SF m a (Event [b]))
forall a. a -> ReaderT Time m a
forall (m :: * -> *) a. Monad m => a -> m a
return (Event [b]
ev', Time -> [(Time, b)] -> SF m a (Event [b])
forall (m :: * -> *) b a.
Monad m =>
Time -> [(Time, b)] -> SF m a (Event [b])
afterEachCat' Time
t' [(Time, b)]
qxs')

    fireEvents :: [b] -> Time -> [(Time, b)] -> ([b], Time, [(Time, b)])
    fireEvents :: forall b. [b] -> Time -> [(Time, b)] -> ([b], Time, [(Time, b)])
fireEvents [b]
ev Time
t []       = ([b]
ev, Time
t, [])
    fireEvents [b]
ev Time
t ((Time, b)
qx:[(Time, b)]
qxs)
        | (Time, b) -> Time
forall a b. (a, b) -> a
fst (Time, b)
qx Time -> Time -> Bool
forall a. Ord a => a -> a -> Bool
< Time
0   = [Char] -> ([b], Time, [(Time, b)])
forall a. HasCallStack => [Char] -> a
error [Char]
"bearriver: afterEachCat: Non-positive period."
        | Time
overdue Time -> Time -> Bool
forall a. Ord a => a -> a -> Bool
>= Time
0 = [b] -> Time -> [(Time, b)] -> ([b], Time, [(Time, b)])
forall b. [b] -> Time -> [(Time, b)] -> ([b], Time, [(Time, b)])
fireEvents ((Time, b) -> b
forall a b. (a, b) -> b
snd (Time, b)
qxb -> [b] -> [b]
forall a. a -> [a] -> [a]
:[b]
ev) Time
overdue [(Time, b)]
qxs
        | Bool
otherwise    = ([b]
ev, Time
t, (Time, b)
qx(Time, b) -> [(Time, b)] -> [(Time, b)]
forall a. a -> [a] -> [a]
:[(Time, b)]
qxs)
      where
        overdue :: Time
overdue = Time
t Time -> Time -> Time
forall a. Num a => a -> a -> a
- (Time, b) -> Time
forall a b. (a, b) -> a
fst (Time, b)
qx


-- | Delay for events. (Consider it a triggered after, hence /basic/.)
delayEvent :: Monad m => Time -> SF m (Event a) (Event a)
delayEvent :: forall (m :: * -> *) a. Monad m => Time -> SF m (Event a) (Event a)
delayEvent Time
q | Time
q Time -> Time -> Bool
forall a. Ord a => a -> a -> Bool
< Time
0     = [Char] -> SF m (Event a) (Event a)
forall a. HasCallStack => [Char] -> a
error [Char]
"bearriver: delayEvent: Negative delay."
             | Time
q Time -> Time -> Bool
forall a. Eq a => a -> a -> Bool
== Time
0    = SF m (Event a) (Event a)
forall (m :: * -> *) a. Monad m => SF m a a
identity
             | Bool
otherwise = Time -> SF m (Event a) (Event [a])
forall (m :: * -> *) a.
Monad m =>
Time -> SF m (Event a) (Event [a])
delayEventCat Time
q SF m (Event a) (Event [a])
-> MSF (ClockInfo m) (Event [a]) (Event a)
-> SF m (Event a) (Event a)
forall {k} (cat :: k -> k -> *) (a :: k) (b :: k) (c :: k).
Category cat =>
cat a b -> cat b c -> cat a c
>>> (Event [a] -> Event a) -> MSF (ClockInfo m) (Event [a]) (Event a)
forall b c. (b -> c) -> MSF (ClockInfo m) b c
forall (a :: * -> * -> *) b c. Arrow a => (b -> c) -> a b c
arr (([a] -> a) -> Event [a] -> Event a
forall a b. (a -> b) -> Event a -> Event b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap [a] -> a
forall a. HasCallStack => [a] -> a
head)

-- | Delay an event by a given delta and catenate events that occur so closely
-- so as to be /inseparable/.
delayEventCat :: Monad m => Time -> SF m (Event a) (Event [a])
delayEventCat :: forall (m :: * -> *) a.
Monad m =>
Time -> SF m (Event a) (Event [a])
delayEventCat Time
q | Time
q Time -> Time -> Bool
forall a. Ord a => a -> a -> Bool
< Time
0     = [Char] -> SF m (Event a) (Event [a])
forall a. HasCallStack => [Char] -> a
error [Char]
"bearriver: delayEventCat: Negative delay."
                | Time
q Time -> Time -> Bool
forall a. Eq a => a -> a -> Bool
== Time
0    = (Event a -> Event [a]) -> SF m (Event a) (Event [a])
forall b c. (b -> c) -> MSF (ClockInfo m) b c
forall (a :: * -> * -> *) b c. Arrow a => (b -> c) -> a b c
arr ((a -> [a]) -> Event a -> Event [a]
forall a b. (a -> b) -> Event a -> Event b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap (a -> [a] -> [a]
forall a. a -> [a] -> [a]
:[]))
                | Bool
otherwise = (Event a -> ClockInfo m (Event [a], SF m (Event a) (Event [a])))
-> SF m (Event a) (Event [a])
forall (m :: * -> *) a b. (a -> m (b, MSF m a b)) -> MSF m a b
MSF Event a -> ClockInfo m (Event [a], SF m (Event a) (Event [a]))
forall {m :: * -> *} {a}.
Monad m =>
Event a
-> ReaderT
     Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
noPendingEvent
  where
    noPendingEvent :: Event a
-> ReaderT
     Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
noPendingEvent Event a
e
          = (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
-> ReaderT
     Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
forall a. a -> ReaderT Time m a
forall (m :: * -> *) a. Monad m => a -> m a
return
               ( Event [a]
forall a. Event a
NoEvent
               , case Event a
e of
                   Event a
NoEvent -> (Event a
 -> ReaderT
      Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
-> MSF (ReaderT Time m) (Event a) (Event [a])
forall (m :: * -> *) a b. (a -> m (b, MSF m a b)) -> MSF m a b
MSF ((Event a
  -> ReaderT
       Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
 -> MSF (ReaderT Time m) (Event a) (Event [a]))
-> (Event a
    -> ReaderT
         Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
-> MSF (ReaderT Time m) (Event a) (Event [a])
forall a b. (a -> b) -> a -> b
$ Event a
-> ReaderT
     Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
noPendingEvent
                   Event a
x -> (Event a
 -> ReaderT
      Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
-> MSF (ReaderT Time m) (Event a) (Event [a])
forall (m :: * -> *) a b. (a -> m (b, MSF m a b)) -> MSF m a b
MSF (Time
-> [(Time, a)]
-> [(Time, a)]
-> Time
-> a
-> Event a
-> ReaderT
     Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
pendingEvents (-Time
q) [] [] (-Time
q) a
x)
               )

    -- tNext is the present time w.r.t. the next scheduled event.
    -- tLast is the present time w.r.t. the last scheduled event.
    -- In the event queues, events are associated with their time
    -- w.r.t. to preceding event (positive).
    pendingEvents :: Time
-> [(Time, a)]
-> [(Time, a)]
-> Time
-> a
-> Event a
-> ReaderT
     Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
pendingEvents Time
tLast [(Time, a)]
rqxs [(Time, a)]
qxs Time
tNext a
x = Event a
-> ReaderT
     Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
forall {m :: * -> *}.
Monad m =>
Event a
-> ReaderT
     Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
tf -- True
      where
        tf :: Event a
-> ReaderT
     Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
tf Event a
e = do Time
dt <- ReaderT Time m Time
forall (m :: * -> *) r. Monad m => ReaderT r m r
ask
                  (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
-> ReaderT
     Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
forall a. a -> ReaderT Time m a
forall (m :: * -> *) a. Monad m => a -> m a
return (Time
-> Event a
-> (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
tf' Time
dt Event a
e)

        tf' :: Time
-> Event a
-> (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
tf' Time
dt Event a
e
            | Time
tNext' Time -> Time -> Bool
forall a. Ord a => a -> a -> Bool
>= Time
0
            = Event a
-> Time
-> [(Time, a)]
-> [(Time, a)]
-> Time
-> [a]
-> (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
emitEventsScheduleNext Event a
e Time
tLast' [(Time, a)]
rqxs [(Time, a)]
qxs Time
tNext' [a
x]
            | Bool
otherwise
            = (Event [a]
forall a. Event a
NoEvent, (Event a
 -> ReaderT
      Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
-> MSF (ReaderT Time m) (Event a) (Event [a])
forall (m :: * -> *) a b. (a -> m (b, MSF m a b)) -> MSF m a b
MSF (Time
-> [(Time, a)]
-> [(Time, a)]
-> Time
-> a
-> Event a
-> ReaderT
     Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
pendingEvents Time
tLast'' [(Time, a)]
rqxs' [(Time, a)]
qxs Time
tNext' a
x))
          where
            tNext' :: Time
tNext' = Time
tNext Time -> Time -> Time
forall a. Num a => a -> a -> a
+ Time
dt
            tLast' :: Time
tLast' = Time
tLast Time -> Time -> Time
forall a. Num a => a -> a -> a
+ Time
dt
            (Time
tLast'', [(Time, a)]
rqxs') =
              case Event a
e of
                Event a
NoEvent  -> (Time
tLast', [(Time, a)]
rqxs)
                Event a
x' -> (-Time
q,     (Time
tLast' Time -> Time -> Time
forall a. Num a => a -> a -> a
+ Time
q, a
x') (Time, a) -> [(Time, a)] -> [(Time, a)]
forall a. a -> [a] -> [a]
: [(Time, a)]
rqxs)

    -- tNext is the present time w.r.t. the *scheduled* time of the event that
    -- is about to be emitted (i.e. >= 0).
    -- The time associated with any event at the head of the event queue is also
    -- given w.r.t. the event that is about to be emitted.  Thus, tNext - q' is
    -- the present time w.r.t. the event at the head of the event queue.
    emitEventsScheduleNext :: Event a
-> Time
-> [(Time, a)]
-> [(Time, a)]
-> Time
-> [a]
-> (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
emitEventsScheduleNext Event a
e Time
_ [] [] Time
_ [a]
rxs =
      ( [a] -> Event [a]
forall a. a -> Event a
Event ([a] -> [a]
forall a. [a] -> [a]
reverse [a]
rxs)
      , case Event a
e of
          Event a
NoEvent -> (Event a
 -> ReaderT
      Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
-> MSF (ReaderT Time m) (Event a) (Event [a])
forall (m :: * -> *) a b. (a -> m (b, MSF m a b)) -> MSF m a b
MSF ((Event a
  -> ReaderT
       Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
 -> MSF (ReaderT Time m) (Event a) (Event [a]))
-> (Event a
    -> ReaderT
         Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
-> MSF (ReaderT Time m) (Event a) (Event [a])
forall a b. (a -> b) -> a -> b
$ Event a
-> ReaderT
     Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
noPendingEvent
          Event a
x -> (Event a
 -> ReaderT
      Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
-> MSF (ReaderT Time m) (Event a) (Event [a])
forall (m :: * -> *) a b. (a -> m (b, MSF m a b)) -> MSF m a b
MSF ((Event a
  -> ReaderT
       Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
 -> MSF (ReaderT Time m) (Event a) (Event [a]))
-> (Event a
    -> ReaderT
         Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
-> MSF (ReaderT Time m) (Event a) (Event [a])
forall a b. (a -> b) -> a -> b
$ Time
-> [(Time, a)]
-> [(Time, a)]
-> Time
-> a
-> Event a
-> ReaderT
     Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
pendingEvents (-Time
q) [] [] (-Time
q) a
x
      )
    emitEventsScheduleNext Event a
e Time
tLast [(Time, a)]
rqxs [] Time
tNext [a]
rxs =
      Event a
-> Time
-> [(Time, a)]
-> [(Time, a)]
-> Time
-> [a]
-> (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
emitEventsScheduleNext Event a
e Time
tLast [] ([(Time, a)] -> [(Time, a)]
forall a. [a] -> [a]
reverse [(Time, a)]
rqxs) Time
tNext [a]
rxs
    emitEventsScheduleNext Event a
e Time
tLast [(Time, a)]
rqxs ((Time
q', a
x') : [(Time, a)]
qxs') Time
tNext [a]
rxs
      | Time
q' Time -> Time -> Bool
forall a. Ord a => a -> a -> Bool
> Time
tNext = ( [a] -> Event [a]
forall a. a -> Event a
Event ([a] -> [a]
forall a. [a] -> [a]
reverse [a]
rxs)
                     , case Event a
e of
                         Event a
NoEvent -> (Event a
 -> ReaderT
      Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
-> MSF (ReaderT Time m) (Event a) (Event [a])
forall (m :: * -> *) a b. (a -> m (b, MSF m a b)) -> MSF m a b
MSF ((Event a
  -> ReaderT
       Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
 -> MSF (ReaderT Time m) (Event a) (Event [a]))
-> (Event a
    -> ReaderT
         Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
-> MSF (ReaderT Time m) (Event a) (Event [a])
forall a b. (a -> b) -> a -> b
$
                           Time
-> [(Time, a)]
-> [(Time, a)]
-> Time
-> a
-> Event a
-> ReaderT
     Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
pendingEvents Time
tLast
                                         [(Time, a)]
rqxs
                                         [(Time, a)]
qxs'
                                         (Time
tNext Time -> Time -> Time
forall a. Num a => a -> a -> a
- Time
q')
                                         a
x'
                         Event a
x'' -> (Event a
 -> ReaderT
      Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
-> MSF (ReaderT Time m) (Event a) (Event [a])
forall (m :: * -> *) a b. (a -> m (b, MSF m a b)) -> MSF m a b
MSF ((Event a
  -> ReaderT
       Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
 -> MSF (ReaderT Time m) (Event a) (Event [a]))
-> (Event a
    -> ReaderT
         Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a])))
-> MSF (ReaderT Time m) (Event a) (Event [a])
forall a b. (a -> b) -> a -> b
$
                           Time
-> [(Time, a)]
-> [(Time, a)]
-> Time
-> a
-> Event a
-> ReaderT
     Time m (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
pendingEvents (-Time
q)
                                         ((Time
tLast Time -> Time -> Time
forall a. Num a => a -> a -> a
+ Time
q, a
x'') (Time, a) -> [(Time, a)] -> [(Time, a)]
forall a. a -> [a] -> [a]
: [(Time, a)]
rqxs)
                                         [(Time, a)]
qxs'
                                         (Time
tNext Time -> Time -> Time
forall a. Num a => a -> a -> a
- Time
q')
                                         a
x'
                      )
      | Bool
otherwise  = Event a
-> Time
-> [(Time, a)]
-> [(Time, a)]
-> Time
-> [a]
-> (Event [a], MSF (ReaderT Time m) (Event a) (Event [a]))
emitEventsScheduleNext Event a
e
                                            Time
tLast
                                            [(Time, a)]
rqxs
                                            [(Time, a)]
qxs'
                                            (Time
tNext Time -> Time -> Time
forall a. Num a => a -> a -> a
- Time
q')
                                            (a
x' a -> [a] -> [a]
forall a. a -> [a] -> [a]
: [a]
rxs)
-- | A rising edge detector. Useful for things like detecting key presses. It is
-- initialised as /up/, meaning that events occurring at time 0 will not be
-- detected.
edge :: Monad m => SF m Bool (Event ())
edge :: forall (m :: * -> *). Monad m => SF m Bool (Event ())
edge = Bool -> SF m Bool (Event ())
forall (m :: * -> *). Monad m => Bool -> SF m Bool (Event ())
edgeFrom Bool
True

-- | A rising edge detector that can be initialized as up ('True', meaning that
-- events occurring at time 0 will not be detected) or down ('False', meaning
-- that events occurring at time 0 will be detected).
iEdge :: Monad m => Bool -> SF m Bool (Event ())
iEdge :: forall (m :: * -> *). Monad m => Bool -> SF m Bool (Event ())
iEdge = Bool -> SF m Bool (Event ())
forall (m :: * -> *). Monad m => Bool -> SF m Bool (Event ())
edgeFrom

-- | A rising edge detector that can be initialized as up ('True', meaning that
-- events occurring at time 0 will not be detected) or down ('False', meaning
-- that events occurring at time 0 will be detected).
edgeFrom :: Monad m => Bool -> SF m Bool (Event())
edgeFrom :: forall (m :: * -> *). Monad m => Bool -> SF m Bool (Event ())
edgeFrom Bool
prev = (Bool
 -> ClockInfo m (Event (), MSF (ReaderT Time m) Bool (Event ())))
-> MSF (ReaderT Time m) Bool (Event ())
forall (m :: * -> *) a b. (a -> m (b, MSF m a b)) -> MSF m a b
MSF ((Bool
  -> ClockInfo m (Event (), MSF (ReaderT Time m) Bool (Event ())))
 -> MSF (ReaderT Time m) Bool (Event ()))
-> (Bool
    -> ClockInfo m (Event (), MSF (ReaderT Time m) Bool (Event ())))
-> MSF (ReaderT Time m) Bool (Event ())
forall a b. (a -> b) -> a -> b
$ \Bool
a -> do
  let res :: Event ()
res | Bool
prev      = Event ()
forall a. Event a
NoEvent
          | Bool
a         = () -> Event ()
forall a. a -> Event a
Event ()
          | Bool
otherwise = Event ()
forall a. Event a
NoEvent
      ct :: MSF (ReaderT Time m) Bool (Event ())
ct  = Bool -> MSF (ReaderT Time m) Bool (Event ())
forall (m :: * -> *). Monad m => Bool -> SF m Bool (Event ())
edgeFrom Bool
a
  (Event (), MSF (ReaderT Time m) Bool (Event ()))
-> ClockInfo m (Event (), MSF (ReaderT Time m) Bool (Event ()))
forall a. a -> ReaderT Time m a
forall (m :: * -> *) a. Monad m => a -> m a
return (Event ()
res, MSF (ReaderT Time m) Bool (Event ())
ct)

-- | Like 'edge', but parameterized on the tag value.
edgeTag :: Monad m => a -> SF m Bool (Event a)
edgeTag :: forall (m :: * -> *) a. Monad m => a -> SF m Bool (Event a)
edgeTag a
a = SF m Bool (Event ())
forall (m :: * -> *). Monad m => SF m Bool (Event ())
edge SF m Bool (Event ())
-> MSF (ClockInfo m) (Event ()) (Event a)
-> MSF (ClockInfo m) Bool (Event a)
forall {k} (cat :: k -> k -> *) (a :: k) (b :: k) (c :: k).
Category cat =>
cat a b -> cat b c -> cat a c
>>> (Event () -> Event a) -> MSF (ClockInfo m) (Event ()) (Event a)
forall b c. (b -> c) -> MSF (ClockInfo m) b c
forall (a :: * -> * -> *) b c. Arrow a => (b -> c) -> a b c
arr (Event () -> a -> Event a
forall a b. Event a -> b -> Event b
`tag` a
a)

-- | Edge detector particularized for detecting transitions on a 'Maybe' signal
-- from 'Nothing' to 'Just'.
edgeJust :: Monad m => SF m (Maybe a) (Event a)
edgeJust :: forall (m :: * -> *) a. Monad m => SF m (Maybe a) (Event a)
edgeJust = (Maybe a -> Maybe a -> Maybe a)
-> Maybe a -> SF m (Maybe a) (Event a)
forall (m :: * -> *) a b.
Monad m =>
(a -> a -> Maybe b) -> a -> SF m a (Event b)
edgeBy Maybe a -> Maybe a -> Maybe a
forall {a} {a}. Maybe a -> Maybe a -> Maybe a
isJustEdge (a -> Maybe a
forall a. a -> Maybe a
Just a
forall a. HasCallStack => a
undefined)
  where
    isJustEdge :: Maybe a -> Maybe a -> Maybe a
isJustEdge Maybe a
Nothing  Maybe a
Nothing     = Maybe a
forall a. Maybe a
Nothing
    isJustEdge Maybe a
Nothing  ma :: Maybe a
ma@(Just a
_) = Maybe a
ma
    isJustEdge (Just a
_) (Just a
_)    = Maybe a
forall a. Maybe a
Nothing
    isJustEdge (Just a
_) Maybe a
Nothing     = Maybe a
forall a. Maybe a
Nothing

-- | Edge detector parameterized on the edge detection function and initial
-- state, i.e., the previous input sample. The first argument to the edge
-- detection function is the previous sample, the second the current one.
edgeBy :: Monad m => (a -> a -> Maybe b) -> a -> SF m a (Event b)
edgeBy :: forall (m :: * -> *) a b.
Monad m =>
(a -> a -> Maybe b) -> a -> SF m a (Event b)
edgeBy a -> a -> Maybe b
isEdge a
aPrev = (a -> ClockInfo m (Event b, MSF (ReaderT Time m) a (Event b)))
-> MSF (ReaderT Time m) a (Event b)
forall (m :: * -> *) a b. (a -> m (b, MSF m a b)) -> MSF m a b
MSF ((a -> ClockInfo m (Event b, MSF (ReaderT Time m) a (Event b)))
 -> MSF (ReaderT Time m) a (Event b))
-> (a -> ClockInfo m (Event b, MSF (ReaderT Time m) a (Event b)))
-> MSF (ReaderT Time m) a (Event b)
forall a b. (a -> b) -> a -> b
$ \a
a ->
  (Event b, MSF (ReaderT Time m) a (Event b))
-> ClockInfo m (Event b, MSF (ReaderT Time m) a (Event b))
forall a. a -> ReaderT Time m a
forall (m :: * -> *) a. Monad m => a -> m a
return (Maybe b -> Event b
forall a. Maybe a -> Event a
maybeToEvent (a -> a -> Maybe b
isEdge a
aPrev a
a), (a -> a -> Maybe b) -> a -> MSF (ReaderT Time m) a (Event b)
forall (m :: * -> *) a b.
Monad m =>
(a -> a -> Maybe b) -> a -> SF m a (Event b)
edgeBy a -> a -> Maybe b
isEdge a
a)

-- * Stateful event suppression

-- | Suppression of initial (at local time 0) event.
notYet :: Monad m => SF m (Event a) (Event a)
notYet :: forall (m :: * -> *) a. Monad m => SF m (Event a) (Event a)
notYet = Bool
-> MSF (ClockInfo m) (Event a, Bool) (Event a, Bool)
-> MSF (ClockInfo m) (Event a) (Event a)
forall (m :: * -> *) c a b.
Monad m =>
c -> MSF m (a, c) (b, c) -> MSF m a b
feedback Bool
False (MSF (ClockInfo m) (Event a, Bool) (Event a, Bool)
 -> MSF (ClockInfo m) (Event a) (Event a))
-> MSF (ClockInfo m) (Event a, Bool) (Event a, Bool)
-> MSF (ClockInfo m) (Event a) (Event a)
forall a b. (a -> b) -> a -> b
$ ((Event a, Bool) -> (Event a, Bool))
-> MSF (ClockInfo m) (Event a, Bool) (Event a, Bool)
forall b c. (b -> c) -> MSF (ClockInfo m) b c
forall (a :: * -> * -> *) b c. Arrow a => (b -> c) -> a b c
arr (\(Event a
e, Bool
c) ->
  if Bool
c then (Event a
e, Bool
True) else (Event a
forall a. Event a
NoEvent, Bool
True))

-- | Suppress all but the first event.
once :: Monad m => SF m (Event a) (Event a)
once :: forall (m :: * -> *) a. Monad m => SF m (Event a) (Event a)
once = Int -> SF m (Event a) (Event a)
forall (m :: * -> *) a. Monad m => Int -> SF m (Event a) (Event a)
takeEvents Int
1

-- | Suppress all but the first n events.
takeEvents :: Monad m => Int -> SF m (Event a) (Event a)
takeEvents :: forall (m :: * -> *) a. Monad m => Int -> SF m (Event a) (Event a)
takeEvents Int
n | Int
n Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
<= Int
0 = SF m (Event a) (Event a)
forall (m :: * -> *) a b. Monad m => SF m a (Event b)
never
takeEvents Int
n = SF m (Event a) (Event a, Event a)
-> (a -> SF m (Event a) (Event a)) -> SF m (Event a) (Event a)
forall (m :: * -> *) a b c.
Monad m =>
SF m a (b, Event c) -> (c -> SF m a b) -> SF m a b
dSwitch ((Event a -> (Event a, Event a))
-> SF m (Event a) (Event a, Event a)
forall b c. (b -> c) -> MSF (ClockInfo m) b c
forall (a :: * -> * -> *) b c. Arrow a => (b -> c) -> a b c
arr Event a -> (Event a, Event a)
forall a. a -> (a, a)
dup) (SF m (Event a) (Event a) -> a -> SF m (Event a) (Event a)
forall a b. a -> b -> a
const (Event a
forall a. Event a
NoEvent Event a -> SF m (Event a) (Event a) -> SF m (Event a) (Event a)
forall (m :: * -> *) a b. Monad m => a -> SF m a b -> SF m a b
>-- Int -> SF m (Event a) (Event a)
forall (m :: * -> *) a. Monad m => Int -> SF m (Event a) (Event a)
takeEvents (Int
n Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
1)))

-- | Suppress first n events.
dropEvents :: Monad m => Int -> SF m (Event a) (Event a)
dropEvents :: forall (m :: * -> *) a. Monad m => Int -> SF m (Event a) (Event a)
dropEvents Int
n | Int
n Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
<= Int
0 = SF m (Event a) (Event a)
forall (m :: * -> *) a. Monad m => SF m a a
identity
dropEvents Int
n =
  -- Here dSwitch or switch does not really matter.
  SF m (Event a) (Event a, Event a)
-> (a -> SF m (Event a) (Event a)) -> SF m (Event a) (Event a)
forall (m :: * -> *) a b c.
Monad m =>
SF m a (b, Event c) -> (c -> SF m a b) -> SF m a b
dSwitch (SF m (Event a) (Event a)
forall (m :: * -> *) a b. Monad m => SF m a (Event b)
never SF m (Event a) (Event a)
-> SF m (Event a) (Event a) -> SF m (Event a) (Event a, Event a)
forall b c c'.
MSF (ClockInfo m) b c
-> MSF (ClockInfo m) b c' -> MSF (ClockInfo m) b (c, c')
forall (a :: * -> * -> *) b c c'.
Arrow a =>
a b c -> a b c' -> a b (c, c')
&&& SF m (Event a) (Event a)
forall (m :: * -> *) a. Monad m => SF m a a
identity)
          (SF m (Event a) (Event a) -> a -> SF m (Event a) (Event a)
forall a b. a -> b -> a
const (Event a
forall a. Event a
NoEvent Event a -> SF m (Event a) (Event a) -> SF m (Event a) (Event a)
forall (m :: * -> *) a b. Monad m => a -> SF m a b -> SF m a b
>-- Int -> SF m (Event a) (Event a)
forall (m :: * -> *) a. Monad m => Int -> SF m (Event a) (Event a)
dropEvents (Int
n Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
1)))

-- ** Hybrid continuous-to-discrete SF combinators.

-- | Event source with a single occurrence at time 0. The value of the event is
-- obtained by sampling the input at that time.
snap :: Monad m => SF m a (Event a)
snap :: forall (m :: * -> *) a. Monad m => SF m a (Event a)
snap =
  -- switch ensures that the entire signal function will become just
  -- "constant" once the sample has been taken.
  SF m a (Event a, Event a)
-> (a -> SF m a (Event a)) -> SF m a (Event a)
forall (m :: * -> *) a b c.
Monad m =>
SF m a (b, Event c) -> (c -> SF m a b) -> SF m a b
switch (SF m a (Event a)
forall (m :: * -> *) a b. Monad m => SF m a (Event b)
never SF m a (Event a) -> SF m a (Event a) -> SF m a (Event a, Event a)
forall b c c'.
MSF (ClockInfo m) b c
-> MSF (ClockInfo m) b c' -> MSF (ClockInfo m) b (c, c')
forall (a :: * -> * -> *) b c c'.
Arrow a =>
a b c -> a b c' -> a b (c, c')
&&& (SF m a a
forall (m :: * -> *) a. Monad m => SF m a a
identity SF m a a
-> MSF (ClockInfo m) a (Event ())
-> MSF (ClockInfo m) a (a, Event ())
forall b c c'.
MSF (ClockInfo m) b c
-> MSF (ClockInfo m) b c' -> MSF (ClockInfo m) b (c, c')
forall (a :: * -> * -> *) b c c'.
Arrow a =>
a b c -> a b c' -> a b (c, c')
&&& () -> MSF (ClockInfo m) a (Event ())
forall (m :: * -> *) b a. Monad m => b -> SF m a (Event b)
now () MSF (ClockInfo m) a (a, Event ())
-> ((a, Event ()) -> Event a) -> SF m a (Event a)
forall (a :: * -> * -> *) b c d.
Arrow a =>
a b c -> (c -> d) -> a b d
>>^ \(a
a, Event ()
e) -> Event ()
e Event () -> a -> Event a
forall a b. Event a -> b -> Event b
`tag` a
a)) a -> SF m a (Event a)
forall (m :: * -> *) b a. Monad m => b -> SF m a (Event b)
now

-- | Event source with a single occurrence at or as soon after (local) time
-- @tEv@ as possible. The value of the event is obtained by sampling the input a
-- that time.
snapAfter :: Monad m => Time -> SF m a (Event a)
snapAfter :: forall (m :: * -> *) a. Monad m => Time -> SF m a (Event a)
snapAfter Time
tEv =
  SF m a (Event a, Event a)
-> (a -> SF m a (Event a)) -> SF m a (Event a)
forall (m :: * -> *) a b c.
Monad m =>
SF m a (b, Event c) -> (c -> SF m a b) -> SF m a b
switch (SF m a (Event a)
forall (m :: * -> *) a b. Monad m => SF m a (Event b)
never SF m a (Event a) -> SF m a (Event a) -> SF m a (Event a, Event a)
forall b c c'.
MSF (ClockInfo m) b c
-> MSF (ClockInfo m) b c' -> MSF (ClockInfo m) b (c, c')
forall (a :: * -> * -> *) b c c'.
Arrow a =>
a b c -> a b c' -> a b (c, c')
&&& (SF m a a
forall (m :: * -> *) a. Monad m => SF m a a
identity SF m a a
-> MSF (ClockInfo m) a (Event ())
-> MSF (ClockInfo m) a (a, Event ())
forall b c c'.
MSF (ClockInfo m) b c
-> MSF (ClockInfo m) b c' -> MSF (ClockInfo m) b (c, c')
forall (a :: * -> * -> *) b c c'.
Arrow a =>
a b c -> a b c' -> a b (c, c')
&&& Time -> () -> MSF (ClockInfo m) a (Event ())
forall (m :: * -> *) b a. Monad m => Time -> b -> SF m a (Event b)
after Time
tEv () MSF (ClockInfo m) a (a, Event ())
-> ((a, Event ()) -> Event a) -> SF m a (Event a)
forall (a :: * -> * -> *) b c d.
Arrow a =>
a b c -> (c -> d) -> a b d
>>^ \(a
a, Event ()
e) -> Event ()
e Event () -> a -> Event a
forall a b. Event a -> b -> Event b
`tag` a
a)) a -> SF m a (Event a)
forall (m :: * -> *) b a. Monad m => b -> SF m a (Event b)
now

-- | Sample a signal at regular intervals.
sample :: Monad m => Time -> SF m a (Event a)
sample :: forall (m :: * -> *) a. Monad m => Time -> SF m a (Event a)
sample Time
pEv = SF m a a
forall (m :: * -> *) a. Monad m => SF m a a
identity SF m a a
-> MSF (ClockInfo m) a (Event ())
-> MSF (ClockInfo m) a (a, Event ())
forall b c c'.
MSF (ClockInfo m) b c
-> MSF (ClockInfo m) b c' -> MSF (ClockInfo m) b (c, c')
forall (a :: * -> * -> *) b c c'.
Arrow a =>
a b c -> a b c' -> a b (c, c')
&&& Time -> () -> MSF (ClockInfo m) a (Event ())
forall (m :: * -> *) b a. Monad m => Time -> b -> SF m a (Event b)
repeatedly Time
pEv () MSF (ClockInfo m) a (a, Event ())
-> ((a, Event ()) -> Event a) -> MSF (ClockInfo m) a (Event a)
forall (a :: * -> * -> *) b c d.
Arrow a =>
a b c -> (c -> d) -> a b d
>>^ \(a
a, Event ()
e) -> Event ()
e Event () -> a -> Event a
forall a b. Event a -> b -> Event b
`tag` a
a

-- | Window sampling.
--
-- First argument is the window length wl, second is the sampling interval t.
-- The output list should contain (min (truncate (T/t) wl)) samples, where T is
-- the time the signal function has been running. This requires some care in
-- case of sparse sampling. In case of sparse sampling, the current input value
-- is assumed to have been present at all points where sampling was missed.
sampleWindow :: Monad m => Int -> Time -> SF m a (Event [a])
sampleWindow :: forall (m :: * -> *) a.
Monad m =>
Int -> Time -> SF m a (Event [a])
sampleWindow Int
wl Time
q =
    SF m a a
forall (m :: * -> *) a. Monad m => SF m a a
identity SF m a a
-> MSF (ClockInfo m) a (Event [()])
-> MSF (ClockInfo m) a (a, Event [()])
forall b c c'.
MSF (ClockInfo m) b c
-> MSF (ClockInfo m) b c' -> MSF (ClockInfo m) b (c, c')
forall (a :: * -> * -> *) b c c'.
Arrow a =>
a b c -> a b c' -> a b (c, c')
&&& [(Time, ())] -> MSF (ClockInfo m) a (Event [()])
forall (m :: * -> *) b a.
Monad m =>
[(Time, b)] -> SF m a (Event [b])
afterEachCat ((Time, ()) -> [(Time, ())]
forall a. a -> [a]
repeat (Time
q, ()))
    MSF (ClockInfo m) a (a, Event [()])
-> MSF (ClockInfo m) (a, Event [()]) (Event [a])
-> MSF (ClockInfo m) a (Event [a])
forall {k} (cat :: k -> k -> *) (a :: k) (b :: k) (c :: k).
Category cat =>
cat a b -> cat b c -> cat a c
>>> ((a, Event [()]) -> Event [a])
-> MSF (ClockInfo m) (a, Event [()]) (Event [a])
forall b c. (b -> c) -> MSF (ClockInfo m) b c
forall (a :: * -> * -> *) b c. Arrow a => (b -> c) -> a b c
arr (\(a
a, Event [()]
e) -> ([()] -> [a]) -> Event [()] -> Event [a]
forall a b. (a -> b) -> Event a -> Event b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap ((() -> a) -> [()] -> [a]
forall a b. (a -> b) -> [a] -> [b]
map (a -> () -> a
forall a b. a -> b -> a
const a
a)) Event [()]
e)
    MSF (ClockInfo m) (a, Event [()]) (Event [a])
-> MSF (ClockInfo m) (Event [a]) (Event [a])
-> MSF (ClockInfo m) (a, Event [()]) (Event [a])
forall {k} (cat :: k -> k -> *) (a :: k) (b :: k) (c :: k).
Category cat =>
cat a b -> cat b c -> cat a c
>>> ([a] -> [a] -> [a])
-> [a] -> MSF (ClockInfo m) (Event [a]) (Event [a])
forall (m :: * -> *) b a.
Monad m =>
(b -> a -> b) -> b -> SF m (Event a) (Event b)
accumBy [a] -> [a] -> [a]
forall {a}. [a] -> [a] -> [a]
updateWindow []
  where
    updateWindow :: [a] -> [a] -> [a]
updateWindow [a]
w [a]
as = Int -> [a] -> [a]
forall a. Int -> [a] -> [a]
drop (Int -> Int -> Int
forall a. Ord a => a -> a -> a
max ([a] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [a]
w' Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
wl) Int
0) [a]
w'
      where
        w' :: [a]
w' = [a]
w [a] -> [a] -> [a]
forall {a}. [a] -> [a] -> [a]
++ [a]
as

-- * Repetition and switching

-- | Makes an event source recurring by restarting it as soon as it has an
-- occurrence.
recur :: Monad m => SF m a (Event b) -> SF m a (Event b)
recur :: forall (m :: * -> *) a b.
Monad m =>
SF m a (Event b) -> SF m a (Event b)
recur SF m a (Event b)
sfe = SF m a (Event b, Event b)
-> (b -> SF m a (Event b)) -> SF m a (Event b)
forall (m :: * -> *) a b c.
Monad m =>
SF m a (b, Event c) -> (c -> SF m a b) -> SF m a b
switch (SF m a (Event b)
forall (m :: * -> *) a b. Monad m => SF m a (Event b)
never SF m a (Event b) -> SF m a (Event b) -> SF m a (Event b, Event b)
forall b c c'.
MSF (ClockInfo m) b c
-> MSF (ClockInfo m) b c' -> MSF (ClockInfo m) b (c, c')
forall (a :: * -> * -> *) b c c'.
Arrow a =>
a b c -> a b c' -> a b (c, c')
&&& SF m a (Event b)
sfe) ((b -> SF m a (Event b)) -> SF m a (Event b))
-> (b -> SF m a (Event b)) -> SF m a (Event b)
forall a b. (a -> b) -> a -> b
$ \b
b -> b -> Event b
forall a. a -> Event a
Event b
b Event b -> SF m a (Event b) -> SF m a (Event b)
forall (m :: * -> *) b a. Monad m => b -> SF m a b -> SF m a b
--> SF m a (Event b) -> SF m a (Event b)
forall (m :: * -> *) a b.
Monad m =>
SF m a (Event b) -> SF m a (Event b)
recur (Event b
forall a. Event a
NoEvent Event b -> SF m a (Event b) -> SF m a (Event b)
forall (m :: * -> *) b a. Monad m => b -> SF m a b -> SF m a b
--> SF m a (Event b)
sfe)

-- | Apply the first SF until it produces an event, and, afterwards, switch to
-- the second SF. This is just a convenience function, used to write what
-- sometimes is more understandable switch-based code.
andThen :: Monad m => SF m a (Event b) -> SF m a (Event b) -> SF m a (Event b)
SF m a (Event b)
sfe1 andThen :: forall (m :: * -> *) a b.
Monad m =>
SF m a (Event b) -> SF m a (Event b) -> SF m a (Event b)
`andThen` SF m a (Event b)
sfe2 = SF m a (Event b, Event b)
-> (b -> SF m a (Event b)) -> SF m a (Event b)
forall (m :: * -> *) a b c.
Monad m =>
SF m a (b, Event c) -> (c -> SF m a b) -> SF m a b
dSwitch (SF m a (Event b)
sfe1 SF m a (Event b)
-> (Event b -> (Event b, Event b)) -> SF m a (Event b, Event b)
forall (a :: * -> * -> *) b c d.
Arrow a =>
a b c -> (c -> d) -> a b d
>>^ Event b -> (Event b, Event b)
forall a. a -> (a, a)
dup) (SF m a (Event b) -> b -> SF m a (Event b)
forall a b. a -> b -> a
const SF m a (Event b)
sfe2)