{-# LANGUAGE GADTs, Rank2Types, CPP #-} ----------------------------------------------------------------------------------------- -- | -- Module : FRP.Yampa.Switches -- Copyright : (c) Antony Courtney and Henrik Nilsson, Yale University, 2003 -- License : BSD-style (see the LICENSE file in the distribution) -- -- Maintainer : ivan.perez@keera.co.uk -- Stability : provisional -- Portability : non-portable (GHC extensions) -- -- Switches allow you to change the signal function being applied. -- -- The basic idea of switching is fromed by combining a subordinate signal function -- and a signal function continuation parameterised over some initial data. -- -- For example, the most basic switch has the following signature: -- -- @switch :: SF a (b, Event c) -> (c -> SF a b) -> SF a b@ -- -- which indicates that it has two parameters: a signal function -- that produces an output and indicates, with an event, when it is time to -- switch, and a signal function that starts with the residual data left by the -- first SF in the event and continues onwards. -- -- Note that switching occurs, at most, once. If you want something to switch -- repeatedly, you need to loop. However, some switches are immediate (meaning -- that the second SF is started at the time of switching). If you use the same -- SF that originally provoked the switch, you are very likely to fall into an -- infinite loop. module FRP.Yampa.Switches ( -- Re-exported module, classes, and types -- * Switching -- ** Basic switchers switch, dSwitch, -- :: SF a (b, Event c) -> (c -> SF a b) -> SF a b rSwitch, drSwitch, -- :: SF a b -> SF (a,Event (SF a b)) b kSwitch, dkSwitch, -- :: SF a b -- -> SF (a,b) (Event c) -- -> (SF a b -> c -> SF a b) -- -> SF a b -- ** Parallel composition and switching -- *** Parallel composition and switching over collections with broadcasting parB, -- :: Functor col => col (SF a b) -> SF a (col b) pSwitchB,dpSwitchB, -- :: Functor col => -- col (SF a b) -- -> SF (a, col b) (Event c) -- -> (col (SF a b) -> c -> SF a (col b)) -- -> SF a (col b) rpSwitchB,drpSwitchB,-- :: Functor col => -- col (SF a b) -- -> SF (a, Event (col (SF a b)->col (SF a b))) -- (col b) -- *** Parallel composition and switching over collections with general routing par, -- Functor col => -- (forall sf . (a -> col sf -> col (b, sf))) -- -> col (SF b c) -- -> SF a (col c) pSwitch, dpSwitch, -- pSwitch :: Functor col => -- (forall sf . (a -> col sf -> col (b, sf))) -- -> col (SF b c) -- -> SF (a, col c) (Event d) -- -> (col (SF b c) -> d -> SF a (col c)) -- -> SF a (col c) rpSwitch,drpSwitch, -- Functor col => -- (forall sf . (a -> col sf -> col (b, sf))) -- -> col (SF b c) -- -> SF (a, Event (col (SF b c) -> col (SF b c))) -- (col c) -- -- Parallel composition/switchers with "zip" routing parZ, -- [SF a b] -> SF [a] [b] pSwitchZ, -- [SF a b] -> SF ([a],[b]) (Event c) -- -> ([SF a b] -> c -> SF [a] [b]) -> SF [a] [b] dpSwitchZ, -- [SF a b] -> SF ([a],[b]) (Event c) -- -> ([SF a b] -> c ->SF [a] [b]) -> SF [a] [b] rpSwitchZ, -- [SF a b] -> SF ([a], Event ([SF a b]->[SF a b])) [b] drpSwitchZ, -- [SF a b] -> SF ([a], Event ([SF a b]->[SF a b])) [b] -- Application of an SF to a collections parC, -- SF a b -> SF [a] [b] ) where import Control.Arrow import FRP.Yampa.Diagnostics import FRP.Yampa.InternalCore (SF(..), SF'(..), sfTF', sfConst, fdFun, FunDesc(..), sfArrG, DTime) import FRP.Yampa.Basic import FRP.Yampa.Event ------------------------------------------------------------------------------ -- Basic switchers ------------------------------------------------------------------------------ -- !!! Interesting case. It seems we need scoped type variables -- !!! to be able to write down the local type signatures. -- !!! On the other hand, the scoped type variables seem to -- !!! prohibit the kind of unification that is needed for GADTs??? -- !!! Maybe this could be made to wok if it actually WAS known -- !!! that scoped type variables indeed corresponds to universally -- !!! quantified variables? Or if one were to keep track of those -- !!! scoped type variables that actually do? -- !!! -- !!! Find a simpler case to experiment further. For now, elim. -- !!! the free variable. {- -- Basic switch. switch :: SF a (b, Event c) -> (c -> SF a b) -> SF a b switch (SF {sfTF = tf10} :: SF a (b, Event c)) (k :: c -> SF a b) = SF {sfTF = tf0} where tf0 a0 = case tf10 a0 of (sf1, (b0, NoEvent)) -> (switchAux sf1, b0) (_, (_, Event c0)) -> sfTF (k c0) a0 -- It would be nice to optimize further here. E.g. if it would be -- possible to observe the event source only. switchAux :: SF' a (b, Event c) -> SF' a b switchAux (SFId _) = switchAuxA1 id -- New switchAux (SFConst _ (b, NoEvent)) = sfConst b switchAux (SFArr _ f1) = switchAuxA1 f1 switchAux sf1 = SF' tf where tf dt a = case (sfTF' sf1) dt a of (sf1', (b, NoEvent)) -> (switchAux sf1', b) (_, (_, Event c)) -> sfTF (k c) a -- Could be optimized a little bit further by having a case for -- identity, switchAuxI1 -- Note: While switch behaves as a stateless arrow at this point, that -- could change after a switch. Hence, SF' overall. switchAuxA1 :: (a -> (b, Event c)) -> SF' a b switchAuxA1 f1 = sf where sf = SF' tf tf _ a = case f1 a of (b, NoEvent) -> (sf, b) (_, Event c) -> sfTF (k c) a -} -- | Basic switch. -- -- By default, the first signal function is applied. -- -- Whenever the second value in the pair actually is an event, -- the value carried by the event is used to obtain a new signal -- function to be applied *at that time and at future times*. -- -- Until that happens, the first value in the pair is produced -- in the output signal. -- -- Important note: at the time of switching, the second -- signal function is applied immediately. If that second -- SF can also switch at time zero, then a double (nested) -- switch might take place. If the second SF refers to the -- first one, the switch might take place infinitely many -- times and never be resolved. -- -- Remember: The continuation is evaluated strictly at the time -- of switching! switch :: SF a (b, Event c) -> (c -> SF a b) -> SF a b switch (SF {sfTF = tf10}) k = SF {sfTF = tf0} where tf0 a0 = case tf10 a0 of (sf1, (b0, NoEvent)) -> (switchAux sf1 k, b0) (_, (_, Event c0)) -> sfTF (k c0) a0 -- It would be nice to optimize further here. E.g. if it would be -- possible to observe the event source only. switchAux :: SF' a (b, Event c) -> (c -> SF a b) -> SF' a b switchAux (SFArr _ (FDC (b, NoEvent))) _ = sfConst b switchAux (SFArr _ fd1) k = switchAuxA1 (fdFun fd1) k switchAux sf1 k = SF' tf {- if sfIsInv sf1 then switchInv sf1 k else SF' tf False -} where tf dt a = case (sfTF' sf1) dt a of (sf1', (b, NoEvent)) -> (switchAux sf1' k, b) (_, (_, Event c)) -> sfTF (k c) a {- -- Note: subordinate signal function being invariant does NOT -- imply that the overall signal function is. switchInv :: SF' a (b, Event c) -> (c -> SF a b) -> SF' a b switchInv sf1 k = SF' tf False where tf dt a = case (sfTF' sf1) dt a of (sf1', (b, NoEvent)) -> (switchInv sf1' k, b) (_, (_, Event c)) -> sfTF (k c) a -} -- !!! Could be optimized a little bit further by having a case for -- !!! identity, switchAuxI1. But I'd expect identity is so unlikely -- !!! that there is no point. -- Note: While switch behaves as a stateless arrow at this point, that -- could change after a switch. Hence, SF' overall. switchAuxA1 :: (a -> (b, Event c)) -> (c -> SF a b) -> SF' a b switchAuxA1 f1 k = sf where sf = SF' tf -- False tf _ a = case f1 a of (b, NoEvent) -> (sf, b) (_, Event c) -> sfTF (k c) a -- | Switch with delayed observation. -- -- By default, the first signal function is applied. -- -- Whenever the second value in the pair actually is an event, -- the value carried by the event is used to obtain a new signal -- function to be applied *at future times*. -- -- Until that happens, the first value in the pair is produced -- in the output signal. -- -- Important note: at the time of switching, the second -- signal function is used immediately, but the current -- input is fed by it (even though the actual output signal -- value at time 0 is discarded). -- -- If that second SF can also switch at time zero, then a -- double (nested) -- switch might take place. If the second SF refers to the -- first one, the switch might take place infinitely many times and never be -- resolved. -- -- Remember: The continuation is evaluated strictly at the time -- of switching! -- Alternative name: "decoupled switch"? -- (The SFId optimization is highly unlikley to be of much use, but it -- does raise an interesting typing issue.) dSwitch :: SF a (b, Event c) -> (c -> SF a b) -> SF a b dSwitch (SF {sfTF = tf10}) k = SF {sfTF = tf0} where tf0 a0 = let (sf1, (b0, ec0)) = tf10 a0 in (case ec0 of NoEvent -> dSwitchAux sf1 k Event c0 -> fst (sfTF (k c0) a0), b0) -- It would be nice to optimize further here. E.g. if it would be -- possible to observe the event source only. dSwitchAux :: SF' a (b, Event c) -> (c -> SF a b) -> SF' a b dSwitchAux (SFArr _ (FDC (b, NoEvent))) _ = sfConst b dSwitchAux (SFArr _ fd1) k = dSwitchAuxA1 (fdFun fd1) k dSwitchAux sf1 k = SF' tf {- if sfIsInv sf1 then dSwitchInv sf1 k else SF' tf False -} where tf dt a = let (sf1', (b, ec)) = (sfTF' sf1) dt a in (case ec of NoEvent -> dSwitchAux sf1' k Event c -> fst (sfTF (k c) a), b) {- -- Note: that the subordinate signal function is invariant does NOT -- imply that the overall signal function is. dSwitchInv :: SF' a (b, Event c) -> (c -> SF a b) -> SF' a b dSwitchInv sf1 k = SF' tf False where tf dt a = let (sf1', (b, ec)) = (sfTF' sf1) dt a in (case ec of NoEvent -> dSwitchInv sf1' k Event c -> fst (sfTF (k c) a), b) -} -- !!! Could be optimized a little bit further by having a case for -- !!! identity, switchAuxI1 -- Note: While dSwitch behaves as a stateless arrow at this point, that -- could change after a switch. Hence, SF' overall. dSwitchAuxA1 :: (a -> (b, Event c)) -> (c -> SF a b) -> SF' a b dSwitchAuxA1 f1 k = sf where sf = SF' tf -- False tf _ a = let (b, ec) = f1 a in (case ec of NoEvent -> sf Event c -> fst (sfTF (k c) a), b) -- | Recurring switch. -- -- See <https://wiki.haskell.org/Yampa#Switches> for more -- information on how this switch works. -- !!! Suboptimal. Overall, the constructor is invarying since rSwitch is -- !!! being invoked recursively on a switch. In fact, we don't even care -- !!! whether the subordinate signal function is invarying or not. -- !!! We could make use of a signal function transformer sfInv to -- !!! mark the constructor as invarying. Would that make sense? -- !!! The price would be an extra loop with case analysis. -- !!! The potential gain is fewer case analyses in superior loops. rSwitch :: SF a b -> SF (a, Event (SF a b)) b rSwitch sf = switch (first sf) ((noEventSnd >=-) . rSwitch) {- -- Old version. New is more efficient. Which one is clearer? rSwitch :: SF a b -> SF (a, Event (SF a b)) b rSwitch sf = switch (first sf) rSwitch' where rSwitch' sf = switch (sf *** notYet) rSwitch' -} -- | Recurring switch with delayed observation. -- -- See <https://wiki.haskell.org/Yampa#Switches> for more -- information on how this switch works. drSwitch :: SF a b -> SF (a, Event (SF a b)) b drSwitch sf = dSwitch (first sf) ((noEventSnd >=-) . drSwitch) {- -- Old version. New is more efficient. Which one is clearer? drSwitch :: SF a b -> SF (a, Event (SF a b)) b drSwitch sf = dSwitch (first sf) drSwitch' where drSwitch' sf = dSwitch (sf *** notYet) drSwitch' -} -- | "Call-with-current-continuation" switch. -- -- See <https://wiki.haskell.org/Yampa#Switches> for more -- information on how this switch works. -- !!! Has not been optimized properly. -- !!! Nor has opts been tested! -- !!! Don't forget Inv opts! kSwitch :: SF a b -> SF (a,b) (Event c) -> (SF a b -> c -> SF a b) -> SF a b kSwitch sf10@(SF {sfTF = tf10}) (SF {sfTF = tfe0}) k = SF {sfTF = tf0} where tf0 a0 = let (sf1, b0) = tf10 a0 in case tfe0 (a0, b0) of (sfe, NoEvent) -> (kSwitchAux sf1 sfe, b0) (_, Event c0) -> sfTF (k sf10 c0) a0 -- Same problem as above: must pass k explicitly??? -- kSwitchAux (SFId _) sfe = kSwitchAuxI1 sfe kSwitchAux (SFArr _ (FDC b)) sfe = kSwitchAuxC1 b sfe kSwitchAux (SFArr _ fd1) sfe = kSwitchAuxA1 (fdFun fd1) sfe -- kSwitchAux (SFArrE _ f1) sfe = kSwitchAuxA1 f1 sfe -- kSwitchAux (SFArrEE _ f1) sfe = kSwitchAuxA1 f1 sfe kSwitchAux sf1 (SFArr _ (FDC NoEvent)) = sf1 kSwitchAux sf1 (SFArr _ fde) = kSwitchAuxAE sf1 (fdFun fde) -- kSwitchAux sf1 (SFArrE _ fe) = kSwitchAuxAE sf1 fe -- kSwitchAux sf1 (SFArrEE _ fe) = kSwitchAuxAE sf1 fe kSwitchAux sf1 sfe = SF' tf -- False where tf dt a = let (sf1', b) = (sfTF' sf1) dt a in case (sfTF' sfe) dt (a, b) of (sfe', NoEvent) -> (kSwitchAux sf1' sfe', b) (_, Event c) -> sfTF (k (freeze sf1 dt) c) a {- -- !!! Untested optimization! kSwitchAuxI1 (SFConst _ NoEvent) = sfId kSwitchAuxI1 (SFArr _ fe) = kSwitchAuxI1AE fe kSwitchAuxI1 sfe = SF' tf where tf dt a = case (sfTF' sfe) dt (a, a) of (sfe', NoEvent) -> (kSwitchAuxI1 sfe', a) (_, Event c) -> sfTF (k identity c) a -} -- !!! Untested optimization! kSwitchAuxC1 b (SFArr _ (FDC NoEvent)) = sfConst b kSwitchAuxC1 b (SFArr _ fde) = kSwitchAuxC1AE b (fdFun fde) -- kSwitchAuxC1 b (SFArrE _ fe) = kSwitchAuxC1AE b fe -- kSwitchAuxC1 b (SFArrEE _ fe) = kSwitchAuxC1AE b fe kSwitchAuxC1 b sfe = SF' tf -- False where tf dt a = case (sfTF' sfe) dt (a, b) of (sfe', NoEvent) -> (kSwitchAuxC1 b sfe', b) (_, Event c) -> sfTF (k (constant b) c) a -- !!! Untested optimization! kSwitchAuxA1 f1 (SFArr _ (FDC NoEvent)) = sfArrG f1 kSwitchAuxA1 f1 (SFArr _ fde) = kSwitchAuxA1AE f1 (fdFun fde) -- kSwitchAuxA1 f1 (SFArrE _ fe) = kSwitchAuxA1AE f1 fe -- kSwitchAuxA1 f1 (SFArrEE _ fe) = kSwitchAuxA1AE f1 fe kSwitchAuxA1 f1 sfe = SF' tf -- False where tf dt a = let b = f1 a in case (sfTF' sfe) dt (a, b) of (sfe', NoEvent) -> (kSwitchAuxA1 f1 sfe', b) (_, Event c) -> sfTF (k (arr f1) c) a -- !!! Untested optimization! -- kSwitchAuxAE (SFId _) fe = kSwitchAuxI1AE fe kSwitchAuxAE (SFArr _ (FDC b)) fe = kSwitchAuxC1AE b fe kSwitchAuxAE (SFArr _ fd1) fe = kSwitchAuxA1AE (fdFun fd1) fe -- kSwitchAuxAE (SFArrE _ f1) fe = kSwitchAuxA1AE f1 fe -- kSwitchAuxAE (SFArrEE _ f1) fe = kSwitchAuxA1AE f1 fe kSwitchAuxAE sf1 fe = SF' tf -- False where tf dt a = let (sf1', b) = (sfTF' sf1) dt a in case fe (a, b) of NoEvent -> (kSwitchAuxAE sf1' fe, b) Event c -> sfTF (k (freeze sf1 dt) c) a {- -- !!! Untested optimization! kSwitchAuxI1AE fe = SF' tf -- False where tf dt a = case fe (a, a) of NoEvent -> (kSwitchAuxI1AE fe, a) Event c -> sfTF (k identity c) a -} -- !!! Untested optimization! kSwitchAuxC1AE b fe = SF' tf -- False where tf _ a = case fe (a, b) of NoEvent -> (kSwitchAuxC1AE b fe, b) Event c -> sfTF (k (constant b) c) a -- !!! Untested optimization! kSwitchAuxA1AE f1 fe = SF' tf -- False where tf _ a = let b = f1 a in case fe (a, b) of NoEvent -> (kSwitchAuxA1AE f1 fe, b) Event c -> sfTF (k (arr f1) c) a -- | 'kSwitch' with delayed observation. -- -- See <https://wiki.haskell.org/Yampa#Switches> for more -- information on how this switch works. -- !!! Has not been optimized properly. Should be like kSwitch. dkSwitch :: SF a b -> SF (a,b) (Event c) -> (SF a b -> c -> SF a b) -> SF a b dkSwitch sf10@(SF {sfTF = tf10}) (SF {sfTF = tfe0}) k = SF {sfTF = tf0} where tf0 a0 = let (sf1, b0) = tf10 a0 in (case tfe0 (a0, b0) of (sfe, NoEvent) -> dkSwitchAux sf1 sfe (_, Event c0) -> fst (sfTF (k sf10 c0) a0), b0) dkSwitchAux sf1 (SFArr _ (FDC NoEvent)) = sf1 dkSwitchAux sf1 sfe = SF' tf -- False where tf dt a = let (sf1', b) = (sfTF' sf1) dt a in (case (sfTF' sfe) dt (a, b) of (sfe', NoEvent) -> dkSwitchAux sf1' sfe' (_, Event c) -> fst (sfTF (k (freeze sf1 dt) c) a), b) ------------------------------------------------------------------------------ -- Parallel composition and switching over collections with broadcasting ------------------------------------------------------------------------------ -- | Tuple a value up with every element of a collection of signal -- functions. broadcast :: Functor col => a -> col sf -> col (a, sf) broadcast a = fmap (\sf -> (a, sf)) -- !!! Hmm. We should really optimize here. -- !!! Check for Arr in parallel! -- !!! Check for Arr FDE in parallel!!! -- !!! Check for EP in parallel!!!!! -- !!! Cf &&&. -- !!! But how??? All we know is that the collection is a functor ... -- !!! Maybe that kind of generality does not make much sense for -- !!! par and parB? (Although it is niceto be able to switch into a -- !!! par or parB from within a pSwitch[B].) -- !!! If we had a parBList, that could be defined in terms of &&&, surely? -- !!! E.g. -- !!! parBList [] = constant [] -- !!! parBList (sf:sfs) = sf &&& parBList sfs >>> arr (\(x,xs) -> x:xs) -- !!! -- !!! This ought to optimize quite well. E.g. -- !!! parBList [arr1,arr2,arr3] -- !!! = arr1 &&& parBList [arr2,arr3] >>> arrX -- !!! = arr1 &&& (arr2 &&& parBList [arr3] >>> arrX) >>> arrX -- !!! = arr1 &&& (arr2 &&& (arr3 &&& parBList [] >>> arrX) >>> arrX) >>> arrX -- !!! = arr1 &&& (arr2 &&& (arr3C >>> arrX) >>> arrX) >>> arrX -- !!! = arr1 &&& (arr2 &&& (arr3CcpX) >>> arrX) >>> arrX -- !!! = arr1 &&& (arr23CcpX >>> arrX) >>> arrX -- !!! = arr1 &&& (arr23CcpXcpX) >>> arrX -- !!! = arr123CcpXcpXcpX -- | Spatial parallel composition of a signal function collection. -- Given a collection of signal functions, it returns a signal -- function that 'broadcast's its input signal to every element -- of the collection, to return a signal carrying a collection -- of outputs. See 'par'. -- -- For more information on how parallel composition works, check -- <http://haskell.cs.yale.edu/wp-content/uploads/2011/01/yampa-arcade.pdf> parB :: Functor col => col (SF a b) -> SF a (col b) parB = par broadcast -- | Parallel switch (dynamic collection of signal functions spatially composed -- in parallel). See 'pSwitch'. -- -- For more information on how parallel composition works, check -- <http://haskell.cs.yale.edu/wp-content/uploads/2011/01/yampa-arcade.pdf> pSwitchB :: Functor col => col (SF a b) -> SF (a,col b) (Event c) -> (col (SF a b)->c-> SF a (col b)) -> SF a (col b) pSwitchB = pSwitch broadcast -- | Delayed parallel switch with broadcasting (dynamic collection of -- signal functions spatially composed in parallel). See 'dpSwitch'. -- -- For more information on how parallel composition works, check -- <http://haskell.cs.yale.edu/wp-content/uploads/2011/01/yampa-arcade.pdf> dpSwitchB :: Functor col => col (SF a b) -> SF (a,col b) (Event c) -> (col (SF a b)->c->SF a (col b)) -> SF a (col b) dpSwitchB = dpSwitch broadcast -- For more information on how parallel composition works, check -- <http://haskell.cs.yale.edu/wp-content/uploads/2011/01/yampa-arcade.pdf> rpSwitchB :: Functor col => col (SF a b) -> SF (a, Event (col (SF a b) -> col (SF a b))) (col b) rpSwitchB = rpSwitch broadcast -- For more information on how parallel composition works, check -- <http://haskell.cs.yale.edu/wp-content/uploads/2011/01/yampa-arcade.pdf> drpSwitchB :: Functor col => col (SF a b) -> SF (a, Event (col (SF a b) -> col (SF a b))) (col b) drpSwitchB = drpSwitch broadcast ------------------------------------------------------------------------------ -- Parallel composition and switching over collections with general routing ------------------------------------------------------------------------------ -- | Spatial parallel composition of a signal function collection parameterized -- on the routing function. -- par :: Functor col => (forall sf . (a -> col sf -> col (b, sf))) -- ^ Determines the input to each signal function -- in the collection. IMPORTANT! The routing function MUST -- preserve the structure of the signal function collection. -> col (SF b c) -- ^ Signal function collection. -> SF a (col c) par rf sfs0 = SF {sfTF = tf0} where tf0 a0 = let bsfs0 = rf a0 sfs0 sfcs0 = fmap (\(b0, sf0) -> (sfTF sf0) b0) bsfs0 sfs = fmap fst sfcs0 cs0 = fmap snd sfcs0 in (parAux rf sfs, cs0) -- Internal definition. Also used in parallel switchers. parAux :: Functor col => (forall sf . (a -> col sf -> col (b, sf))) -> col (SF' b c) -> SF' a (col c) parAux rf sfs = SF' tf -- True where tf dt a = let bsfs = rf a sfs sfcs' = fmap (\(b, sf) -> (sfTF' sf) dt b) bsfs sfs' = fmap fst sfcs' cs = fmap snd sfcs' in (parAux rf sfs', cs) -- | Parallel switch parameterized on the routing function. This is the most -- general switch from which all other (non-delayed) switches in principle -- can be derived. The signal function collection is spatially composed in -- parallel and run until the event signal function has an occurrence. Once -- the switching event occurs, all signal function are "frozen" and their -- continuations are passed to the continuation function, along with the -- event value. -- -- rf ......... Routing function: determines the input to each signal function -- in the collection. IMPORTANT! The routing function has an -- obligation to preserve the structure of the signal function -- collection. -- sfs0 ....... Signal function collection. -- sfe0 ....... Signal function generating the switching event. -- k .......... Continuation to be invoked once event occurs. -- Returns the resulting signal function. -- -- !!! Could be optimized on the event source being SFArr, SFArrE, SFArrEE pSwitch :: Functor col => (forall sf . (a -> col sf -> col (b, sf))) -- ^ Routing function: determines the input to each signal function -- in the collection. IMPORTANT! The routing function has an -- obligation to preserve the structure of the signal function -- collection. -> col (SF b c) -- ^ Signal function collection. -> SF (a, col c) (Event d) -- ^ Signal function generating the switching event. -> (col (SF b c) -> d -> SF a (col c)) -- ^ Continuation to be invoked once event occurs. -> SF a (col c) pSwitch rf sfs0 sfe0 k = SF {sfTF = tf0} where tf0 a0 = let bsfs0 = rf a0 sfs0 sfcs0 = fmap (\(b0, sf0) -> (sfTF sf0) b0) bsfs0 sfs = fmap fst sfcs0 cs0 = fmap snd sfcs0 in case (sfTF sfe0) (a0, cs0) of (sfe, NoEvent) -> (pSwitchAux sfs sfe, cs0) (_, Event d0) -> sfTF (k sfs0 d0) a0 pSwitchAux sfs (SFArr _ (FDC NoEvent)) = parAux rf sfs pSwitchAux sfs sfe = SF' tf -- False where tf dt a = let bsfs = rf a sfs sfcs' = fmap (\(b, sf) -> (sfTF' sf) dt b) bsfs sfs' = fmap fst sfcs' cs = fmap snd sfcs' in case (sfTF' sfe) dt (a, cs) of (sfe', NoEvent) -> (pSwitchAux sfs' sfe', cs) (_, Event d) -> sfTF (k (freezeCol sfs dt) d) a -- | Parallel switch with delayed observation parameterized on the routing -- function. -- -- The collection argument to the function invoked on the -- switching event is of particular interest: it captures the -- continuations of the signal functions running in the collection -- maintained by 'dpSwitch' at the time of the switching event, -- thus making it possible to preserve their state across a switch. -- Since the continuations are plain, ordinary signal functions, -- they can be resumed, discarded, stored, or combined with -- other signal functions. -- !!! Could be optimized on the event source being SFArr, SFArrE, SFArrEE. -- dpSwitch :: Functor col => (forall sf . (a -> col sf -> col (b, sf))) -- ^ Routing function. Its purpose is -- to pair up each running signal function in the collection -- maintained by 'dpSwitch' with the input it is going to see -- at each point in time. All the routing function can do is specify -- how the input is distributed. -> col (SF b c) -- ^ Initial collection of signal functions. -> SF (a, col c) (Event d) -- ^ Signal function that observes the external -- input signal and the output signals from the collection in order -- to produce a switching event. -> (col (SF b c) -> d -> SF a (col c)) -- ^ The fourth argument is a function that is invoked when the -- switching event occurs, yielding a new signal function to switch -- into based on the collection of signal functions previously -- running and the value carried by the switching event. This -- allows the collection to be updated and then switched back -- in, typically by employing 'dpSwitch' again. -> SF a (col c) dpSwitch rf sfs0 sfe0 k = SF {sfTF = tf0} where tf0 a0 = let bsfs0 = rf a0 sfs0 sfcs0 = fmap (\(b0, sf0) -> (sfTF sf0) b0) bsfs0 cs0 = fmap snd sfcs0 in (case (sfTF sfe0) (a0, cs0) of (sfe, NoEvent) -> dpSwitchAux (fmap fst sfcs0) sfe (_, Event d0) -> fst (sfTF (k sfs0 d0) a0), cs0) dpSwitchAux sfs (SFArr _ (FDC NoEvent)) = parAux rf sfs dpSwitchAux sfs sfe = SF' tf -- False where tf dt a = let bsfs = rf a sfs sfcs' = fmap (\(b, sf) -> (sfTF' sf) dt b) bsfs cs = fmap snd sfcs' in (case (sfTF' sfe) dt (a, cs) of (sfe', NoEvent) -> dpSwitchAux (fmap fst sfcs') sfe' (_, Event d) -> fst (sfTF (k (freezeCol sfs dt) d) a), cs) -- Recurring parallel switch parameterized on the routing function. -- rf ......... Routing function: determines the input to each signal function -- in the collection. IMPORTANT! The routing function has an -- obligation to preserve the structure of the signal function -- collection. -- sfs ........ Initial signal function collection. -- Returns the resulting signal function. rpSwitch :: Functor col => (forall sf . (a -> col sf -> col (b, sf))) -> col (SF b c) -> SF (a, Event (col (SF b c) -> col (SF b c))) (col c) rpSwitch rf sfs = pSwitch (rf . fst) sfs (arr (snd . fst)) $ \sfs' f -> noEventSnd >=- rpSwitch rf (f sfs') {- rpSwitch rf sfs = pSwitch (rf . fst) sfs (arr (snd . fst)) k where k sfs f = rpSwitch' (f sfs) rpSwitch' sfs = pSwitch (rf . fst) sfs (NoEvent --> arr (snd . fst)) k -} -- Recurring parallel switch with delayed observation parameterized on the -- routing function. drpSwitch :: Functor col => (forall sf . (a -> col sf -> col (b, sf))) -> col (SF b c) -> SF (a, Event (col (SF b c) -> col (SF b c))) (col c) drpSwitch rf sfs = dpSwitch (rf . fst) sfs (arr (snd . fst)) $ \sfs' f -> noEventSnd >=- drpSwitch rf (f sfs') {- drpSwitch rf sfs = dpSwitch (rf . fst) sfs (arr (snd . fst)) k where k sfs f = drpSwitch' (f sfs) drpSwitch' sfs = dpSwitch (rf . fst) sfs (NoEvent-->arr (snd . fst)) k -} ------------------------------------------------------------------------------ -- * Parallel composition/switchers with "zip" routing ------------------------------------------------------------------------------ parZ :: [SF a b] -> SF [a] [b] parZ = par (safeZip "parZ") pSwitchZ :: [SF a b] -> SF ([a],[b]) (Event c) -> ([SF a b] -> c -> SF [a] [b]) -> SF [a] [b] pSwitchZ = pSwitch (safeZip "pSwitchZ") dpSwitchZ :: [SF a b] -> SF ([a],[b]) (Event c) -> ([SF a b] -> c ->SF [a] [b]) -> SF [a] [b] dpSwitchZ = dpSwitch (safeZip "dpSwitchZ") rpSwitchZ :: [SF a b] -> SF ([a], Event ([SF a b] -> [SF a b])) [b] rpSwitchZ = rpSwitch (safeZip "rpSwitchZ") drpSwitchZ :: [SF a b] -> SF ([a], Event ([SF a b] -> [SF a b])) [b] drpSwitchZ = drpSwitch (safeZip "drpSwitchZ") -- IPerez: This is actually unsafezip. Zip is actually safe. It works -- regardless of which list is smallest. This version of zip is right-biased: -- the second list determines the size of the final list. safeZip :: String -> [a] -> [b] -> [(a,b)] safeZip fn l1 l2 = safeZip' l1 l2 where safeZip' :: [a] -> [b] -> [(a, b)] safeZip' _ [] = [] safeZip' as (b:bs) = (head' as, b) : safeZip' (tail' as) bs head' :: [a] -> a head' [] = err head' (a:_) = a tail' :: [a] -> [a] tail' [] = err tail' (_:as) = as err :: a err = usrErr "FRP.Yampa.Switches" fn "Input list too short." -- Freezes a "running" signal function, i.e., turns it into a continuation in -- the form of a plain signal function. freeze :: SF' a b -> DTime -> SF a b freeze sf dt = SF {sfTF = (sfTF' sf) dt} freezeCol :: Functor col => col (SF' a b) -> DTime -> col (SF a b) freezeCol sfs dt = fmap (`freeze` dt) sfs -- Apply an SF to every element of a list. parC :: SF a b -> SF [a] [b] parC sf = SF $ \as -> let os = map (sfTF sf) as bs = map snd os sfs = map fst os in (parCAux sfs, bs) -- Internal definition. Also used in parallel switchers. parCAux :: [SF' a b] -> SF' [a] [b] parCAux sfs = SF' tf where tf dt as = let os = map (\(a,sf) -> sfTF' sf dt a) $ safeZip "parC" as sfs bs = map snd os sfcs = map fst os in (listSeq sfcs `seq` parCAux sfcs, listSeq bs) listSeq :: [a] -> [a] listSeq x = x `seq` (listSeq' x) listSeq' :: [a] -> [a] listSeq' [] = [] listSeq' rs@(a:as) = a `seq` listSeq' as `seq` rs -- Vim modeline -- vim:set tabstop=8 expandtab: