fp2/week2/mart/oldold/old/StdMaybeMonad.icl

   1 implementation module StdMaybeMonad
   2
   3 import StdMonad
   4
   5 :: Maybe a = Nothing | Just a
   6
   7 instance return Maybe where return x       = Just x
   8 instance >>=    Maybe where >>= (Just x) f = f x
   9                             >>= Nothing  f = Nothing
  10 instance fail   Maybe where fail           = Nothing