On Tue, Oct 1, 2013 at 12:15 PM, Dan Burton <danburton.email@gmail.com> wrote:

From what you've said, it sounds like you can already write:

serverSide :: IO a -> Form a

This seems elegant enough to me for your needs. Just encourage it as an idiom specific to Forms.

myBlogForm = Blog <$> titleForm <*> serverSide getCurrentTime <*> contentsForm

Could you abstract `serverSide` out into a typeclass, such as ApplicativeIO? Sure. but why bother? The point is, you've got the specialization you need already.

Yes, I agree that to simply solve the problem in yesod-form, this would be a great solution. But as to "why bother" with ApplicativeIO: my point in sending this email was to see if other people have been bothered by this, and if it's therefore worth coming up with a general purpose solution. If there's no real interest in it, I don't see a need to create such a general solution. On the other hand, if people think this is worth a general ApplicativeIO class, I'd be happy to use that instead of defining an ad-hoc function in yesod-form.

Thanks to everyone for this great discussion, I'm thoroughly enjoying following it.

Michael