/* remember to import Interlude instead! */
import Prelude ()

/* ugly, but a real function would block subsequent imports */
#define BUG(C_,M_) (report_bug (C_) (M_) __FILE__ __LINE__)

#define head (\xs -> case xs of { (x:_) -> x ; _ -> BUG("head","empty list")})
#define tail (\xs -> case xs of { (_:x) -> x ; _ -> BUG("tail","empty list")})

#define at (let {at_ (y:_) 0  = y; at_ (y:ys) n = if n>0 then at_ ys (n-1) else BUG("at","negative index"); at_ _ _ = BUG ("at","index too large")} in \a x -> at_ a x)
#define read (\s -> case [ x | (x,t) <- reads s, ("","") <- lex t] of { [x] -> x ; [] -> BUG("read","no parse"); _ -> BUG("read","ambigous parse")})
#define fromJust (\x -> case x of Just a -> a; Nothing -> BUG("fromJust","Nothing"))
#define undefined (error ("Hit 'undefined' in "++__FILE__++", "++show (__LINE__ :: Int)))
#define undefinedM (fail ("Hit 'undefinedM' in "++__FILE__++", "++show (__LINE__ :: Int)))

#define MESSAGE ""