just out of curiosity, which is the proper idiom? trace a = r <- catch a (\e -> putStr "exceptional\n" >> throw e) trace a = r <- catch a (\e -> putStr "exceptional\n" >> ioError e) I am worried that one might subtly change the semantics of an execption depending on how it was originally thrown... but i am uncertain how. probably some obscure case involving bottoms. But to be on the safe side, thought I'd ask. John -- --------------------------------------------------------------------------- John Meacham - California Institute of Technology, Alum. - john@foo.net ---------------------------------------------------------------------------