Chaining Applicatives

Question

I wrote this code to append Maybe's:

ghci> (:) <$> Just 5 <*> ((:) <$> Just 100 <*> Just [])
Just [5,100]

Similarly:

ghci> (:) <$> Just 5 <*> ( (:) <$> Just 10 <*> ((:) <$> Just 100 <*> Just []) )
Just [5,10,100]

Is this code idiomatic? Perhaps there's a more concise way to append a bunch of Maybe's together?

Answer 1

Well, while the code surely works, it does look ugly. I would suggest something like this:

sequence [Just 5, Just 10, Just 100]

or, if you really want to use Applicatives instead of Monads,

sequenceA [Just 5, Just 10, Just 100]

from Data.Traversable.

Answer 2

And if you want to use neither Monad nor Applicative you can just use concatMap maybeToList from Data.Maybe.