Add Control.Monad.Trampoline

Author: puffnfresh

src/Control/Monad/Trampoline.purs

@@ -0,0 +1,28 @@
+module Control.Monad.Trampoline where
+
+import Control.Monad.Free
+
+data Delay a = Delay ({} -> a)
+
+instance delayFunctor :: Functor Delay where
+  (<$>) f (Delay g) = Delay (const (f (g {})))
+
+instance delayApply :: Apply Delay where
+  (<*>) (Delay f) (Delay a) = Delay (\{} -> (f {}) (a {}))
+
+instance delayApplicative :: Applicative Delay where
+  pure a = Delay (\{} -> a)
+
+type Trampoline a = Free Delay a
+
+done :: forall a. a -> Trampoline a
+done = Pure
+
+suspend :: forall a. Trampoline a -> Trampoline a
+suspend a = Free (Delay (\{} -> a))
+
+delay :: forall a. ({} -> a) -> Trampoline a
+delay a = Free (done <$> Delay a)
+
+runTrampoline :: forall a. Trampoline a -> a
+runTrampoline = go (\(Delay f) -> f {})