module test
import StdEnv
+import Data.Maybe
+import Data.Functor
+import Control.Applicative
-class arith v
-where
- lit :: a -> v a | toString a
- plus :: (v a) (v a) -> v a | + a
+class expr v where
+ lit :: i -> v i | toString i
+ (+.) infixl 6 :: (v i) (v i) -> v i | + i
-class rtrn v :: (v a) -> v (TaskValue a)
+instance + (v a) | expr v & + a where
+ + l r = l +. r
-:: Print a = P String
-unPrint :: (Print a) -> String
-unPrint (P a) = a
+eval :: (Maybe a) -> Maybe a
+eval x = x
+instance expr Maybe where
+ lit i = Just i
+ +. x y = (+) <$> x <*> y
-:: Eval a = E a
-unEval :: (Eval a) -> a
-unEval (E a) = a
+:: Print a =: Print String
+print :: (Print a) -> String
+print (Print a) = a
+instance expr Print where
+ lit i = Print (toString i)
+ +. (Print l) (Print r) = Print (l +++ "+" +++ r)
-:: TaskValue a = NoValue | Value a Bool
+//printEval :: (A.v: v a | expr v & + (v Int)) -> (Maybe a, String)
+//printEval :: (A.v: v a | expr v & + (v Int)) -> (Maybe a, String)
+//printEval f = (eval f, print f)
-instance arith Print
-where
- lit a = P (toString a)
- plus (P a) (P b) = P (a +++ "+" +++ b)
+printEval` :: (v a) (w a) -> (Maybe a, String) | expr v & expr w
+printEval` f1 f2 = (eval f1, print f2)
-instance arith Eval
-where
- lit a = E a
- plus (E a) (E b) = E (a + b)
+printEval f :== printEval` f f
-instance rtrn Print where rtrn (P a) = P ("Task (" +++ a +++ ")")
-instance rtrn Eval where rtrn (E a) = E (Value a True)
+//x = lit 4 + lit 28
+//y = lit 4 +. lit 28
-class default a :: a
-instance default Int where default = 42
-instance default (TaskValue a) where default = NoValue
+//Mag niet
+//Start = printEval (lit 4 +. lit 38)
+Start :: (Maybe Int, String)
+//Start = printEval (lit 2 + lit 40)
+Start = printEval` expr expr
+//Start = printEval expr
-listItem ::
- (A.v: a -> v (TaskValue b) | rtrn, arith v)
- -> (String, b)
- | +, toString, default b & default a
-listItem mtask =
- ( unPrint (mtask default)
- , default //unEval (mtask default)
- )
+expr :: v Int | expr v & + (v Int)
+expr = lit 4 + lit 38
+//Start = printEval (lit 4 +. lit 38)
-Start :: (String, Int)
-Start = listItem \i->rtrn (lit i)
+//Start = eval (lit 4 + lit 38)
+
+//Mag wel
+//Start = print (lit 4 + lit 38)