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 depends on effects (specifically, the
Effect 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 Effect.Console import Effect (Effect) import Prelude import Signal hello :: Signal String hello = constant "Hello Joe!" helloEffect :: Signal (Effect 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
Effect.Console.log function, which has the type
String -> Effect 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 (Effect 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