gistfile1.hs

term = try prefix <|> try paren <|> try name <|> try number <|> try str <?> "term"

prefix = do o <- prefixOper
            t <- term
            return $ Unary o t

prefixOper = token $ many1 $ oneOf $ nub $ concat prefixes

prefixes :: [String]
prefixes = [ "!"
           , "-"
           , "~"
           , "not" ]