a12/mart/skeleton12.icl

   1 module skeleton12
   2
   3 import StdEnv
   4 import StdMaybe
   5
   6 :: BM a b = {t :: a -> b, f :: b -> a}
   7 bm :: BM a a
   8 bm = {f=id, t=id}
   9 :: Expr a
  10         = Lit a
  11         | (+.) infixl 6 (Expr a) (Expr a)
  12         | (*.) infixl 6 (Expr a) (Expr a)
  13         | Read
  14         | Write (Expr Int)
  15         | XOR (Expr Bool) (Expr Bool)
  16         | Not (Expr Bool)
  17         | E.b: Eq (Expr b) ( Expr b) & == b
  18         | Throw
  19         | Try (Expr a) (Expr a)
  20
  21 class show a :: a [String] -> [String]
  22 instance show (Expr a) where
  23         show (Lit x) l = [toString x:l]
  24         show (x1 +. x2) l = show x1 ["+":show x2 l]
  25         show (x1 *. x2) l = show x1 ["*":show x2 l]
  26         show Read l = ["Read":l]
  27         show (Write x) l = ["Write (":show x [")":l]]
  28         show (XOR x1 x2) l = show x1 ["XOR":show x2 l]
  29         show (Not x) l = ["Not":show x l]
  30         show (Eq x1 x2) l = show x1 ["==":show x2 l]
  31         show Throw l = ["throw":l]
  32         show (Try x1 x2) l = ["Try":show x1 ["Except":show x2 l]]