rank2/test.icl

   1 module test
   2
   3 import StdEnv
   4 import Data.Maybe
   5 import Data.Functor
   6 import Control.Applicative
   7
   8 class expr v where
   9         lit :: i -> v i | toString i
  10         (+.) infixl 6 :: (v i) (v i) -> v i | + i
  11
  12 instance + (v a) | expr v & + a where
  13         + l r = l +. r
  14
  15 eval :: (Maybe a) -> Maybe a
  16 eval x = x
  17 instance expr Maybe where
  18         lit i = Just i
  19         +. x y = (+) <$> x <*> y
  20
  21 :: Print a =: Print String
  22 print :: (Print a) -> String
  23 print (Print a) = a
  24 instance expr Print where
  25         lit i = Print (toString i)
  26         +. (Print l) (Print r) = Print (l +++ "+" +++ r)
  27
  28 //printEval :: (A.v: v a | expr v & + (v Int)) -> (Maybe a, String)
  29 //printEval :: (A.v: v a | expr v & + (v Int)) -> (Maybe a, String)
  30 //printEval f = (eval f, print f)
  31
  32 printEval` :: (v a) (w a) -> (Maybe a, String) | expr v & expr w
  33 printEval` f1 f2 = (eval f1, print f2)
  34
  35 printEval f :== printEval` f f
  36
  37 //x = lit 4 + lit 28
  38 //y = lit 4 +. lit 28
  39
  40 //Mag niet
  41 //Start = printEval (lit 4 +. lit 38)
  42 Start :: (Maybe Int, String)
  43 //Start = printEval (lit 2 + lit 40)
  44 Start = printEval` expr expr
  45 //Start = printEval expr
  46
  47 expr :: v Int | expr v & + (v Int)
  48 expr = lit 4 + lit 38
  49 //Start = printEval (lit 4 +. lit 38)
  50
  51 //Start = eval (lit 4 + lit 38)
  52
  53 //Mag wel
  54 //Start = print (lit 4 + lit 38)