playground: add ability to run code

playground/samples/Hello.newt

@@ -0,0 +1,43 @@
+module Main
+
+-- Monad
+
+class Monad (m : U → U) where
+  bind : {a b} → m a → (a → m b) → m b
+  pure : {a} → a → m a
+
+infixl 1 _>>=_ _>>_
+_>>=_ : {m} {{Monad m}} {a b} -> (m a) -> (a -> m b) -> m b
+ma >>= amb = bind ma amb
+
+_>>_ :  {m} {{Monad m}} {a b} -> m a -> m b -> m b
+ma >> mb = mb
+
+-- I don't want to use an empty type because it would be a proof of void
+ptype World
+
+data IORes : U -> U where
+  MkIORes : {a : U} -> a -> World -> IORes a
+
+IO : U -> U
+IO a = World -> IORes a
+
+
+data Unit : U where
+  MkUnit : Unit
+
+
+instance Monad IO where
+  bind ma mab = \ w => case ma w of
+    MkIORes a w => mab a w
+  pure a = \ w => MkIORes a w
+
+ptype String
+pfunc putStrLn : String -> IO Unit := "(s) => (w) => {
+  console.log(s)
+  return MkIORes(Unit,MkUnit,w)
+}"
+
+main : IO Unit
+main = do
+    putStrLn "hello, world"