typeclasses purescript

typeclasses.purs

module Main where

import Prelude
import Control.Monad.Eff (Eff)
import Control.Monad.Eff.Console (CONSOLE, log)

data MyMaybe a = None | Some a

instance functorMyMaybe :: Functor MyMaybe where
  map _ None  = None
  map f (Some x) = Some (f x)
  --
  -- class (Functor f) <= Apply f where
  --   apply :: forall a b. f (a -> b) -> f a -> f b
--f (a -> b) -> f a -> f b
-- MyMaybe (a -> b) -> MyMaybe a -> MyMaybe b

instance applyMyMaybe :: Apply MyMaybe where
  apply None _ = None
  apply (Some f) x = map f x

instance applicativeMyMaybe :: Applicative MyMaybe where
  pure x = Some x

instance bindMyMaybe :: Bind MyMaybe where
  bind None _ = None
  bind (Some x) f = f x

instance monadMyMaybe :: Monad MyMaybe


-- ///////
data Result fail suc = Success suc | Failure fail

instance functorResult :: Functor (Result a) where
  map _ (Failure x) = Failure x
  map f (Success res) = Success (f res)

instance applyResult :: Apply (Result a) where
  apply (Failure x) _ = Failure x
  apply (Success f) x = map f x

instance applicativeResult :: Applicative (Result a) where
  pure x = Success x

--  bind :: forall a b. m a -> (a -> m b) -> m b
-- Result fail a -> (a -> Result fail b) -> Result fail b
instance bindResult :: Bind (Result a) where
  bind (Failure x) _ = Failure x
  bind (Success x) f = f x

instance monadResult :: Monad (Result a)

main :: forall e. Eff (console :: CONSOLE | e) Unit
main = do
  log "Hello sailor!"