The following script causes an infinite loop when printing the error message provoked by the evaluation of main. Tested with Hugs98 February 2000, both in +98 and -98 mode.

type E s = [T s] data T s = S s | SE (E s) deriving (Show, Eq) p (S s1) (S s2) | s1==s2 = True p t1 (SE e2) = all (q t1) e2 -- p _ _ = error "error in p" q t1 t2 = if p t1 t2 then True else p t2 t1 f (x:xs) (y:ys) | p x y = 1 f _ _ = 2 main = f [S "a"] [SE [S "b"]]

Main> main Program error: {p (Make.Eq (instEq_v23_v1175 instEq_v14) (Eq_default_== (Make.Eq (instEq_v23_v1175 instEq_v14) (Eq_default_== (Make.Eq (instEq_v23_v1175 instEq_ v14) (Eq_default_== (Make.Eq (instEq_v23_v1175 instEq_v14) (Eq_default_== (Make. ...{Interrupted!} Uncommenting the last line in the definition of p fixes the problem, of course. (Although the script is quite contrived, it has been derived from a larger and more realistic program.) Best regards, Dimitur _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.