Re: Proposal: add Control.Monad.whenJust ∷ (Monad m) ⇒ Maybe α→(α→ m ()) → m ()

On Thu, 1 Dec 2011, Mikhail Vorozhtsov wrote:

On 11/30/2011 11:26 PM, Evan Laforge wrote:

...

On Tue, Nov 29, 2011 at 11:11 PM, Liyang HU wrote:

...

This particular pattern crops up a lot for me. Does it for anyone else?

Yep, I have that in my personal library, and use it fairly often.

I prefer it to Foldable.forM_ because it's explicit about the type it takes, forM_ sounds too much like a loop.

Well, it is a loop over collection, which in the case of Maybe can contain at most one element.

Hoogle even lists forM_ and for_ in the second and third position when searching for the signature "Maybe a -> (a-> m ()) -> m ()" Nonetheless I also needed whenJust recently and missed "for_"!