RE: [Haskell-cafe] Parsec (Zero or One of)

Thanks. I can't find optionMaybe in my version 2.1 of Parsec, but in any case, defining my only_prod as only_prod = do { reserved "only"; option [] identifier } or only_prod = do { reserved "only"; identifier <|> return [] } gives the same error responses as before. I will anyway look closer at option. You're right that I don't understand try, but it's not for lack of trying. My examples' use of try though was just a stab at a readable failure. Maybe I should refactor my example. Paul