-- pattern failure
module Exn3 where

instruction primadd "addint" :: Int! -> Int! -> Int!

data Bool   = False | True
data List a = Nil | Cons a (List a)

(+) x y   = case y of y -> case x of x -> primadd x y

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

main
  = case (+) (head Nil) 1 of
      0 -> True
      1 -> False