module shallow

import StdEnv

import Data.Array
import Data.Maybe

:: In a b = In infix 0 a b

(<$>) infixl 4
(<$>) f Nothing = Nothing
(<$>) f (Just a) = Just (f a)

pure a = Just a

(<*>) infixl 4
(<*>) Nothing _ = Nothing
(<*>) (Just f) ma = f <$> ma

(>>=) infixl 1
(>>=) (Just x) k = k x
(>>=) _ _ = Nothing

var :: ((Maybe a) -> In a (Maybe b)) -> Maybe b
var def = let (i In b) = def (pure i) in b

lit :: .a -> Maybe .a
lit a = pure a

(+.) infixl 6 :: (Maybe a) (Maybe a) -> Maybe a | + a
(+.) l r = (+) <$> l <*> r

(++.) infixr 5 :: (Maybe (arr a)) (Maybe (arr a)) -> Maybe (arr a) | Array arr a
(++.) l r = appendArr <$> l <*> r

(!.) infixl 8 :: (Maybe (arr a)) (Maybe Int) -> Maybe a | Array arr a
(!.) a i = a >>= \a->i >>= \i->if (i < 0 || i >= size a) Nothing (Just a.[i])

(=.) infixl 9 :: (Maybe *(arr a)) (Maybe Int, Maybe a) -> (Maybe *(arr a)) | Array arr a
(=.) a (i, e) = a >>= \a->i >>= \i->if (i < 0 || i >= size a) Nothing (update a i <$> e)

//Start = both (var \v=arr {!1,2,3} In v ++. arr {!4,5,6})
//Start = runPrinter (var \v=arr {!1,2,3} In v ++. arr {!4,5,6})
Start =
	( "\n"
//	, var \v={!1,2,3} In v ++. v =. (lit 0, lit 42)
	, "\n"
	, var \v={!1,2,3} In v ++. lit {!4,5,6} =. (lit 0, lit 42)
	, "\n"
	, var \v={!1,2,3} In v ++. lit {!4,5,65}
	, "\n"
	, var \v={!1,2,3} In lit {!4,5,6} ++. v
	, "\n"
//	, runMaybe (var \up0=(\a->a =. (lit 0, lit 0)) In up0 (lit {!4,5,6}))
	)