----------------------------------------------------------------
-- Daan Leijen (c) 2001
--
-- $Revision$
-- $Author$
-- $Date$
----------------------------------------------------------------
module Occur where

data List a = Nil
            | Cons a (List a)

data Bool   = False
            | True


head xs = case xs of Cons x xx -> x

main    = let xs = (let ys = Cons 2 Nil in Cons 1 ys) 
              ys = Cons (head xs) Nil
              zs = Cons (head xs) Nil
          in head ys