RebindableSyntax.purs

module Main where

import Prelude

example1 :: String
example1 = do
  "Do"
  " notation"
  " for"
  " Semigroup"
  where
  bind x f = x <> f unit

(*>) :: forall f a b. (Apply f) => f a -> f b -> f b
(*>) fa fb = const id <$> fa <*> fb

newtype Const a b = Const a

runConst :: forall a b. Const a b -> a
runConst (Const a) = a

instance functorConst :: Functor (Const a) where
  (<$>) _ (Const a) = Const a

instance applyConst :: (Semigroup a) => Apply (Const a) where
  (<*>) (Const a1) (Const a2) = Const (a1 <> a2)

example2 :: Const String Unit
example2 = do
  Const "Do"
  Const " notation"
  Const " for"
  Const " Apply"
  where
  bind x f = x *> f unit

main = do
  Debug.Trace.trace example1
  Debug.Trace.trace $ runConst example2