Applicative and parsec3

Christian Maeder Christian.Maeder at
Fri Jan 28 14:57:11 CET 2011

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
> 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 parsec is not changed I could create a parsec4 package where the
conflicting functions are removed from Text.Parsec.

This will break code that uses "optional" from Text.Parsec. Is there a
need for a renaming of Text.Parsec.Combinator.optional, like "voidOptional"?

Such a function would be better placed inside Control.Applicative though:

 voidOptional v = const () <$> v <|> pure ()


 voidOptional = void . optional

using the new Control.Monad.void.


> --Kazu

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