a3/mart/skeleton3b.icl

   1 module skeleton3b
   2
   3 /*
   4         Advanced Programming.
   5         Skeleton for exercise 3.3 and 3.4.
   6         To be used in a project with the environment Everything,
   7         or StdEnv with an import of StdMaybe from StdLib
   8
   9         Pieter Koopman, pieter@cs.ru.nl
  10 */
  11
  12 import StdEnv, StdGeneric, StdMaybe, GenEq
  13
  14 //------------------ show --------------
  15 generic show_ a :: a [String] -> [String]
  16
  17 show_{|Int|}  i c = [toString i:c]
  18 show_{|Bool|} b c = [toString b:c]
  19
  20 show a = show_{|*|} a []
  21
  22 //------------------ parse --------------
  23
  24 :: Result a :== Maybe (a, [String])
  25
  26 generic parse a :: [String] -> Result a
  27
  28 parse{|Bool|} ["True" :r] = Just (True ,r)
  29 parse{|Bool|} ["False":r] = Just (False,r)
  30 parse{|Bool|} _ = Nothing
  31
  32 //------------------ some data types --------------
  33
  34 :: T            = C
  35 :: Color        = Red | Yellow | Blue
  36 :: Tree a       = Tip | Bin a (Tree a) (Tree a)
  37
  38 //------------------ general useful --------------
  39
  40 instance + String where (+) s t = s+++t
  41 derive bimap Maybe, []
  42
  43 //------------------ to test if parse and show work properly --------------
  44
  45 test :: t -> Bool | gEq{|*|}, show_{|*|}, parse{|*|} t
  46 test x
  47         = case parse{|*|} (show x) of
  48                 Just (y,[])     = x === y
  49                 _                       = False
  50
  51 /**************** End Prelude, add all new code below this line *************************/
  52
  53 //------------------ tests --------------
  54
  55 Start = and [test b \\ b <- [False, True]]