Haskell: Is there an idiomatic way to insert every item in a list into its own list?

问题

I've been using ((:[]) <$> xs) but if there is a more clear way I would love to use it.

edit: so many good answers guys! I don't think I can accept one because they are all good.

回答1:

I believe map return or map pure are good enough.

回答2:

Maybe this?

map (\x -> [x]) xs

Yours can work on any functor I think so this would be more idomatic for just lists.

回答3:

The split package provides a (Data.List.Split.)chunksOf function whose name is, IMO, more meaningful than the various map solutions (even if they are more idiomatic.)

回答4:

You can also use a list comprehension:

[ [x] | x <- theList]

Maybe overkill for such a simple example, but depending on your context, maybe you can merge this step with some further processing of the singleton lists:

[f [x] + 13 | x <- theList]

回答5:

Tongue-in-cheek version:

import Data.List

groupBy (const . const False) xs

回答6:

Using do notation:

do { x <- xs; return [x] }

来源：https://stackoverflow.com/questions/17495179/haskell-is-there-an-idiomatic-way-to-insert-every-item-in-a-list-into-its-own-l