On Thu, Jan 27, 2011 at 4:29 AM, Christian Maeder
Am 27.01.2011 07:16, schrieb Kazu Yamamoto (山本和彦):
Hello,
I'm using parsec3 with the applicative style. Since the functions in Control.Applicative and parsec3 conflicts, I need to use the "hiding" keyword as follows:
import Control.Applicative hiding (many,optional,(<|>)) import Text.Parsec
Another problem:
Control.Applicative.optional corresponds to Text.Parsec.Combinator.optionMaybe whereas Text.Parsec.Combinator.optional returns "()".
This is inconvenient for me. I would like to use them as follows:
import Control.Applicative import Text.Parsec
Christian, the maintainer of parsec3, told me that it is possible to use the functions of Control.Applicative in parsec3 instead of implementing its own functions. But (<|>) of parsec3 is "infixr 1" while that of Control.Applicative is "infixl 3". This may be an issue.
Any ideas to solve this issue?
If we are lucky removing the "infixr 1 <|>" operator does not break too much existing code, because the combination with "infixl 1 >>" needs always brackets, currently. (But a changed interpretation might be hard to notice.)
However, using "a >> b <|> c" would then no longer be an error and interpreted as "a >> (b <|> c)", whereas "a *> b <|> c" would be "(a *> b) <|> c".
I think the change would be worth it, even if painful for existing users. I'm less sure how to go forward for the different "optional" combinators. I would want to port over 'many' to be the one exported from Applicative as well. Antoine
Christian
--Kazu
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