Signal is a lightweight FRP-like library heavily inspired by the Elm Signal implementation. Where possible and sensible, it tries to maintain API equivalence with Elm.
See the Elm documentation for details on usage and principles.
PureScript Usage Patterns
PureScript depends on effects (specifically, the
Eff monad) to manage side effects, where Elm's runtime generally manages them for you.
purescript-signal provides the
Signal.runSignal function for running effectful signals.
module Main where import Control.Monad.Eff.Console import Control.Monad.Eff import Prelude import Signal hello :: Signal String hello = constant "Hello Joe!" helloEffect :: forall eff. Signal (Eff (console :: CONSOLE | eff) Unit) helloEffect = hello ~> log main = runSignal helloEffect
This simple example takes a constant signal which contains the string
"Hello Joe!" and maps it over the
Control.Monad.Eff.Console.log function, which has the type
forall eff. String -> Eff (console :: CONSOLE | eff) Unit, thus taking the
String content of the signal and turning it into an effect which logs the provided string to the user's console.
This gives us a
Signal (Eff (console :: CONSOLE | eff) Unit). We use
runSignal to take the signal of effects and run each effect in turn—in our case, just the one effect which prints
"Hello Joe!" to the console.
- The canonical Elm Mario: https://github.com/michaelficarra/purescript-demo-mario
- Ponies: https://github.com/bodil/purescript-is-magic