PureScript Cheat Sheet

module Main whereimport Prelude-- Type signature + bindinggreet :: String -> Stringgreet name = "Hello, " <> name-- Recordstype User = { name :: String, age :: Int }alice :: Useralice = { name: "Alice", age: 30 }older :: User -> Userolder u = u { age = u.age + 1 }-- Algebraic data typesdata Status = Loading | Success String | Failure Stringdescribe :: Status -> Stringdescribe = case _ of  Loading -> "loading..."  Success msg -> "ok: " <> msg  Failure err -> "error: " <> err

class Describable a where  describe :: a -> Stringinstance describableInt :: Describable Int where  describe n = "Int: " <> show n-- Functor / Applicative / Monad for a custom typedata Box a = Box ainstance functorBox :: Functor Box where  map f (Box a) = Box (f a)instance applyBox :: Apply Box where  apply (Box f) (Box a) = Box (f a)instance applicativeBox :: Applicative Box where  pure = Box

import Effect (Effect)import Effect.Console (log)import Effect.Aff (Aff, launchAff_, delay)import Effect.Class (liftEffect)import Data.Time.Duration (Milliseconds(..))main :: Effect Unitmain = log "hello"asyncTask :: Aff UnitasyncTask = do  liftEffect (log "starting")  delay (Milliseconds 1000.0)  liftEffect (log "done after 1s")runIt :: Effect UnitrunIt = launchAff_ asyncTask

component :: forall q i o m. H.Component q i o mcomponent =  H.mkComponent    { initialState: \_ -> 0    , render    , eval: H.mkEval H.defaultEval { handleAction = handleAction }    }  where  render state =    HH.div_      [ HH.button [ HE.onClick \_ -> Decrement ] [ HH.text "-" ]      , HH.text (show state)      , HH.button [ HE.onClick \_ -> Increment ] [ HH.text "+" ]      ]  handleAction = case _ of    Increment -> H.modify_ (_ + 1)    Decrement -> H.modify_ (_ - 1)