frp

I am trying to create a game using Haskell + Netwire 5 (+ SDL). Now I am working on the output part, where I would like to create wires that read in some game state and output the SDL surfaces to be blitted on screen. However, the problem is that SDL surfaces are contained in IO monad, so any function that creates such surfaces must have type a -> IO b . Of course, arr does not construct a Wire from a -> m b . However, since the type signature of a wire is (Monad m, Monoid e) => Wire s e m a b , it looks quite like a Kleisi Arrow, but I cannot find a suitable constructor for making such a wire

I am testing with the Netwire haskell library and made it work with a simple time wire: import Control.Wire import Prelude hiding ((.), id) import Control.Monad.IO.Class import Data.Functor.Identity import System.IO wire :: (HasTime t s) => Wire s () m a t wire = time run :: (HasTime t s, MonadIO m, Show b, Show e) => Session m s -> Wire s e m a b -> m () run session wire = do (dt, session') <- stepSession session (wt', wire') <- stepWire wire dt $ Right undefined case wt' of -- | Exit Left _ -> return () Right x -> do liftIO $ do putChar '\r' putStr $ either (\ex -> show ex) show wt' hFlush

How should I merge 2 different types of Observable s in RxSwift? For example: var a: Observable<Int> var b: Observable<Void> Observable.of(a,b).merge() is not possible because of type parameter difference. To merge them, they need to have the same type for their Element . So, one option is to throw away their type information and cast to AnyObject . Now they can be merged: let stringSubject = PublishSubject<String>() let stringObservable = stringSubject.asObservable().map { $0 as AnyObject } let intSubject = PublishSubject<Int>() let intObservable = intSubject.asObservable().map { $0 as

1、U盘安装Centos7.6,在物理机上会发生问题： 解决办法： https://blog.csdn.net/qq_28822933/article/details/83472138 https://jingyan.baidu.com/article/19020a0a73b250529d284294.html tab键会出现安装引导vmlinuz initrd.img inst.stage2=hd:LABEL=centOS\x207\x20x86_64 rd.live.check quiet把这段改成vmlinuz initrd.img inst.stage2=hd:/dev/sdb4 quiet 回车 然后ctrl+x就开始安装系统了 2、关闭防火墙： #停止firewallsystemctl stop firewalld.service #禁止firewall开机启动 systemctl disable firewalld.service 3、关闭selinux #临时关闭 setenforce 0 #永久关闭 vi /etc/selinux/config 将SELINUX=enforcing改为SELINUX=disabled 设置后需要重启才能生效 4、修改shh端口：26611 vi /etc/ssh/sshd_config #Port 22 ---->Port

I found this statement while studying Functional Reactive Programming, from "Plugging a Space Leak with an Arrow" by Hai Liu and Paul Hudak ( page 5) : Suppose we wish to define a function that repeats its argument indefinitely: repeat x = x : repeat x or, in lambdas: repeat = λx → x : repeat x This requires O(n) space. But we can achieve O(1) space by writing instead: repeat = λx → let xs = x : xs in xs The difference here seems small but it hugely prompts the space efficiency. Why and how it happens ? The best guess I've made is to evaluate them by hand: r = \x -> x: r x r 3 -> 3: r 3 -> 3: 3:

I just read Deprecating the Observer Pattern and found it absolutely fascinating. What's the status of the Scala.React package described in the document? I found one tarball of a snapshot of Scala.React but there doesn't seem to be much documentation or active maintenance. I also found ScalaFX, which looks like it might be related to reactive programming, but is similarly unmaintained. Are there any projects out there that build on the ideas in this paper to create a GUI framework based on reactives? Alex Cruise UPDATED : As William Harvey points out below , there is recent progress! Like you,

I am looking at messing around with creating a functional reactive framework at some point. I have read quite a lot about it and seen a few examples but I wanted to get a clear idea of what this framework would HAVE to do to be considered an FRP extension/dsl. I'm not really concerned with implementation problems or specifics etc but more as to what would be desired in a perfect world situation. What would be the key operations and qualities of an ideal functional reactive programming language? Conal I'm glad you're starting by asking about a specification rather than implementation first.