- Reactive - Haskell.org

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by Ed Soares 24 Nov '13

24 Nov '13

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Nomes dos aprovados Boca da Mata
by Edson 29 May '13

29 May '13

Nomes dos aprovados Boca da Mata: Primavera do Leste: ALISON MENDONCA DE ALMEIDA, LEISE STELA BRANDAO ARAUJO, FLORIANO LOPES DE JORDAO FILHO, NORMA LIRA FEITOSA SANTOS, JOÃO CARLOS MOREIRA DE CARVALHO, CLODOALDO RODRIGUES CASTRO JUNIOR, MARIA DE FATIMA MONTEIRO DORNELAS, IVONE FERNANDES UCHOA LIMA. SAMUEL BRUNO VIEIRA DE QUEIROZ, EMANUELA CRISTINE PEREIRA FELIX, MÁVIA RANNIELE VASCONCELOS DE LIMA, JOSEFINA NUNES DE ARAÚJO, WALBERT ROCHA LIMA JUNIOR. Joselândia. Boca da Mata, ANNA JESSYCA ANDRADE LACERDA, LUCAS DE PAULA OLIVEIRA, GEORGE FACUNDO RICARDO, RAFAEL WESLEY MENESES MAIA, JOÃO CARLOS MOREIRA DE CARVALHO, DEBORAH LIMA BRAGA, MARIA MARIANA RIBEIRO VIEIRA, JOÃO VICTOR RODRIGUES DE C. MEDEIROS. TATIANA RODRIGUES DE CASTRO MELO, CAIO URBANO CAMURCA, MAIARA FRANKLIN DE AZEVEDO, IAGO TELES GARCIA, RITA PAULA SEVERO PATU. Cachoeira de Pajeú. Nova Fátima e ANA FLÁVIA DA SILVA, LUAN MARLLUS MAIA RAULINO, FRANCISCO MARIO ROCHA DE MELO, PEDRO IGOR GARCIA COSTA, JOÃO CARLOS MOREIRA DE CARVALHO, DANIEL GUIMARAES CORDEIRO, MARIA IVONEIDE DE OLIVEIRA NASCIMENTO, JESICA FREITAS E SILVA. SILVONEIDE DE O, AYSLAN CORDEIRO DO SANTIAGO, LUCIANA SOARES F. DA SILVA, HARIANNE LEITE DE ALENCAR, REJANE SANTA CELESTINA DA SILVA. Itapirapuã.

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Any prior art on (non) spagetti-FRP ?
by luc taesch 26 Mar '13

26 Mar '13

I am just learning FRP ( via reactive-banana) . so possibly opening a topic already mentionned , apologises in advance, and pointers welcomed. I am wondering about "code structuration" ? ie spagetti code for the network 1/ in a non trivial FRP applicaiton, how to manage "modulatity" or structuration of the Network ? ( most of the example I scanned are toy-size). I ca imagine it may not be trvial to find its way around in a large setup ... 2/ what about the separation of "layers". I mean fine, we extract the reactive ness from the GUI, and separate the layout of widgets from the behaviors of these great, but is it to then mingle the UI with the "business part" ( say in banking), and the infrastructure side ( say persistence, comms, transactionnality, etc) in other words, how tdoes the nice abstraction developped ( module/ interface / categoty patterns, monad, etc) coexsit with a netork of FRP event and behaviors ? Any prior art on this ?

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Re: [reactive] switching events = space leak?
by John Lato 11 Feb '13

11 Feb '13

elerea itself doesn't follow the event/behavior distinction, so it looks quite a bit different from the others. Also it doesn't have a particular switch combinator, rather switching behavior is enabled by the use of recursive-do bindings. I think reactive-banana's approach is expressive enough to do as you suggest, but I haven't actually tried it yet. I'd also be interested in a language-agnostic forum for FRP issues. John L From: Don Vincenze <don(a)tr80.com> > > Wow thank you for all these pointers ... I must take the time to look > into these libraries. Stuff like this doesn't come up when you Google > "Functional Reactive Programming" or at least doesn't rank very high. > > > > I'm not sure I understand the sodium approach (couldn't find switch in > elerea). The aging/'trimming' approach in banana seems to rely on the > events being switched into being known from the start, i.e. the point > in time 'switch' starts executing. This way you can dynamically switch > into a static set of events but not dynamically into a dynamic set of > events. > > > > In any case, considering such concerns seem to be transcend individual > libraries/frameworks, you wouldn't know of any mailing list/forum that > is more suitable for this discussion, i.e. a general FRP forum not tied > to any library or one purely focused on theory? > > > > > > On Wed, Feb 6, 2013, at 07:22 PM, John Lato wrote: > > > This can be a serious issue, however most modern FRP implementations > (by which I mean at least reactive-banana, elerea, and sodium) have > solutions. I'm sure elm does as well, but I don't have experience with > it. > > I'm aware of two general approaches. The first, used by elerea and > sodium, enforces that the creation of signaling and switching > constructs happen within a monad. In this case the switching primitive > looks something like > > mSwitch :: Behavior (SGen a) -> SGen (Behavior a) > > this function is responsible for ensuring that signals and behaviors > are represented in the monad, and thus executed. > > The other approach was introduced in Grapefruit, and to my knowledge is > only used in Grapefruit and reactive-banana. Instead of a signal > generation monad, switchable constructs have an extra type parameter > that's used to enforce aging. apfelmus has written a bit about it > at [1]http://apfelmus.nfshost.com/blog/2012/09/03-frp-dynamic-event-swi > tching-0-7.html . Conceptually it's very similar to how the "st" > parameter is used in the ST monad if you're familiar with that. > > as to scaling, it is possible for a reactive network to scale to fairly > large systems, but not all of them do. I've been meaning to blog about > this soon, maybe over the next week or two. > > John L. > > References > > 1. > http://apfelmus.nfshost.com/blog/2012/09/03-frp-dynamic-event-switching-0-7… >

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Re: [reactive] switching events = space leak?
by John Lato 06 Feb '13

06 Feb '13

Hello, > From: Don Vincenze <don(a)tr80.com> > > Hi, > > Is this list still alive ... > > I am trying to learn the theory of FRP by reading the code of this > "reactive" library and Yampa. Not trying to get anything to actually > work here, analyzing implementations of the theory only serve to assess > the viability of it all. I.e. apart from bugs, is it stable, does it > scale? > > For starters I'm worried about space leaks in switching events, e.g. see > the "Event of Events" that's the input to switchE. Those events are > lists that get produced by input producers but not consumed until > they're being switched into, is that right? So during this time of > producing but not consuming the list just grows = there is a space leak? > This can be a serious issue, however most modern FRP implementations (by which I mean at least reactive-banana, elerea, and sodium) have solutions. I'm sure elm does as well, but I don't have experience with it. I'm aware of two general approaches. The first, used by elerea and sodium, enforces that the creation of signaling and switching constructs happen within a monad. In this case the switching primitive looks something like mSwitch :: Behavior (SGen a) -> SGen (Behavior a) this function is responsible for ensuring that signals and behaviors are represented in the monad, and thus executed. The other approach was introduced in Grapefruit, and to my knowledge is only used in Grapefruit and reactive-banana. Instead of a signal generation monad, switchable constructs have an extra type parameter that's used to enforce aging. apfelmus has written a bit about it at http://apfelmus.nfshost.com/blog/2012/09/03-frp-dynamic-event-switching-0-7…. Conceptually it's very similar to how the "st" parameter is used in the ST monad if you're familiar with that. as to scaling, it is possible for a reactive network to scale to fairly large systems, but not all of them do. I've been meaning to blog about this soon, maybe over the next week or two. John L.

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switching events = space leak?
by Don Vincenze 05 Feb '13

05 Feb '13

Hi, Is this list still alive ... I am trying to learn the theory of FRP by reading the code of this "reactive" library and Yampa. Not trying to get anything to actually work here, analyzing implementations of the theory only serve to assess the viability of it all. I.e. apart from bugs, is it stable, does it scale? For starters I'm worried about space leaks in switching events, e.g. see the "Event of Events" that's the input to switchE. Those events are lists that get produced by input producers but not consumed until they're being switched into, is that right? So during this time of producing but not consuming the list just grows = there is a space leak? This is made a bit clearer in the book "The Haskell School of Expression", chapter 15, which as I understand describes the implementation of Yampa, not "reactive". However there isn't a difference between the two in that respect as far as I can read the code, or is there? Such as space leak would not just be a bug but would need some design rework. Don

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FRP applied to music sequencing/ DSP
by Carter Schonwald 14 May '12

14 May '12

Hello All, I'm not sure if this is possible with Reactive or any extant FRP language, but it couldn't hurt to ask the experts :) the high level version of my question is: Does Reactive (or one of its friends) provide the right basic abstractions for doing a subset of - specifying mixing / fades over time (and other DJ related tasks), which conceptual would be constructing some sort of Digraph out of various computational steps (and that are each potentially ) - a mechanism for changing this sequencing in some part of the digraph (ie at some point conceptually changing how the djing is being done) I'm sort of thinking about things wrt the basic djing streams being processed by a circuit / digraph of computations, and there being a meta language for manipulating the circuit. This probably falls totally outside the purview of current FRP as far as I can tell, but if I'm incorrect in thinking that / or some equally appealing approach exists, I'd love to find out! thanks -Carter Schonwald

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Reactive space leak
by Dustin DeWeese 12 Jan '11

12 Jan '11

I cannot get Reactive to behave. I am trying to write a simple program that feeds events to a function and prints 'DING!' when it receives an event from the function. If the function is id or (join . return), it works correctly. If the function is (>>= return), it consumes all of my RAM and does nothing. Why? I've spent several days trying to figure this out. I am using GHC 6.12.1 for x86_64 Linux. import FRP.Reactive import FRP.Reactive.Reactive import FRP.Reactive.Internal.Reactive import FRP.Reactive.Internal.Timing import FRP.Reactive.LegacyAdapters import Control.Monad import Control.Concurrent import Control.Applicative runEventProcessor :: (Event () -> Event ()) -> IO () runEventProcessor f = do clk <- makeClock (sink, ev) <- makeEvent clk forkE (wait clk) . fmap (\_ -> putStrLn "DING!") . f $ ev forever $ do getLine -- wait for <ENTER> sink () putStrLn "<< button pressed >>" threadDelay 100000 -- avoid pressing button too fast wait clk = sleepPast (cGetTime clk) . exactNB explodes1 = runEventProcessor (>>= return) explodes2 = runEventProcessor (join . fmap (Event . pure . pure)) works1 = runEventProcessor (join . return) works2 = runEventProcessor (fmap id) works3 = runEventProcessor (join . Event . pure . pure) -- requires joinE to be exported from FRP.Reactive.PrimReactive -- works4 = runEventProcessor (joinE . return)

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[PATCH] Checkers to work with QuickCheck-2.3
by Mitsutoshi Aoe 01 Sep '10

01 Sep '10

Hi Conal, I wrote a patch for Checkers to work with QuickCheck-2.3. We can't build Reactive now because Checkers can't be built with QuickCheck-2.3. New QuickCheck has Int and Word instances of Arbitrary and CoArbitrary class. Thus we need to remove the duplicate instances from Checkers. -- Mitsutoshi Aoe maoe.maoe(a)gmail.com

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whenE uses much memory
by Conal Elliott 25 Aug '10

25 Aug '10

Oops. The list's spam-filter tossed this note. ---------- Forwarded message ---------- From: Alexander Foremny <alexanderforemny(a)googlemail.com> To: reactive(a)haskell.org Date: Tue, 24 Aug 2010 10:14:11 +0200 Subject: whenE uses much memory Hello, I am trying to write a simple 2D tower defense game using reactive and reactive-glut. I am spawning a wave of creeps that walk around the map and when there are no creeps on the map, I'd like to spawn the next wave. However, I cannot predict at which time there will be no creeps on the maps since each creature might move with different speed. To realize switching anyway I thought I could poll the number of creeps and switch when the number is zero. With that solution I am having serious performance problems. Here's the relevant code: > data World = World { ... } > > wave1 :: Behavior World > > wave2 :: Behavior World > > worldB = wave1 `switcher` fmap (const wave2) (whenE (zeroCreeps wave1) pollE) > where pollE = atTimes [1..] > > zeroCreeps :: Behavior World -> Behavior Bool When running worldB from main I can see the program's memory usage increasing and everything becomes very unresponsive. It seems as if whenE is accumalating all the occurences of the event. The problem seems to boil down to snapshot having the same behavior. > snapshot (pure False) (atTimes [1..]) This piece of code uses very much memory either. Is this due to reactive being broken (I read that somewhere) or is my solution just no solution at all? I am using ghc 6.12.1 with reactive 0.11.5 and reactive-glut 0.1.9. Regards Alexander Foremny

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