On Mon, Mar 12, 2007 at 11:24:48AM +0100, Maxime Henrion wrote:

While using the very nice "option" combinator of Parsec recently, it seemed to me that it would be useful to have a more specific kind of combinator for optional tokens that wraps the token into a Maybe type.

So, that gives:

pmaybe :: GenParser tok st a -> GenParser tok st (Maybe a) pmaybe p = option Nothing (p >>= return . Just)

I've been using it happily with some code of mine. Do people think that it would be generally useful to have in Parsec?

Yes, it would certainly be useful. I think "optional" should work this way, but unfortunately it returns (). Pozdrawiam Tomek