add samples to playground

playground/samples/Prelude.newt

@@ -0,0 +1,47 @@
+module Prelude
+
+data Nat : U where
+  Z : Nat
+  S : Nat -> Nat
+
+data Maybe : U -> U where
+  Just : {a : U} -> a -> Maybe a
+  Nothing : {a : U} -> Maybe a
+
+data Either : U -> U -> U where
+  Left : {a b : U} -> a -> Either a b
+  Right : {a b : U} -> b -> Either a b
+
+-- TODO this is special cased in some languages, maybe for easier
+-- inference? Figure out why.
+
+infixr 0 _$_
+
+-- Currently very noisy in generated code
+_$_ : {a b : U} -> (a -> b) -> a -> b
+f $ a = f a
+
+
+-- Monad
+
+-- TODO stack with Applicative, etc?
+
+data Monad : (U -> U) -> U where
+  MkMonad : { M : U -> U } ->
+            (bind : {A B : U} -> (M A) -> (A -> M B) -> M B) ->
+            (pure : {A : U} -> A -> M A) ->
+            Monad M
+
+infixl 1 _>>=_ _>>_
+_>>=_ : {a b : U} -> {m : U -> U} -> {{x : Monad m}} -> (m a) -> (a -> m b) -> m b
+_>>=_ {a} {b} {m} {{MkMonad bind' _}}  ma amb = bind' {a} {b} ma amb
+
+_>>_ : {a b : U} -> {m : U -> U} -> {{x : Monad m}} -> m a -> m b -> m b
+ma >> mb = mb
+
+pure : {a : U} {m : U -> U} {{_ : Monad m}} -> a -> m a
+pure {_} {_} {{MkMonad _ pure'}} a = pure' a
+
+-- IO
+
+