- `pure`: Polymorphic, works for any `Functor`.

It is OK to have polymorphic folds and length, so what is wrong with pure? 

Adding singleton to Data.List is a breaking change, when Data.Map.singleton was exported unqualified. 

And there is no singleton in Data.List.NonEmpty as well. 

-1 from me.

Best regards,

Andrew

On 12 Aug 2019, at 19:36, Brent Yorgey <byorgey@gmail.com> wrote:

At the risk of completely derailing the conversation, I have always called this the "robot monkey operator".  I fail to see what is so ninja-like about it.

Anyway, I think I am +1 on adding Data.List.singleton.

-Brent

On Mon, Aug 12, 2019, 12:35 PM Zemyla <zemyla@gmail.com> wrote:

I also like the ninja-robot operator, because it's visually
interesting and easy to search for.

Also, if you're importing several libraries which already use
"singleton", then you have to use "List.singleton" every time, which
is far uglier to me.

On Mon, Aug 12, 2019 at 12:03 PM Herbert Valerio Riedel
<hvriedel@gmail.com> wrote:
>
> > - `(:[])`: Subjectively ugly.
>
> I consider "subjectively ugly" to be a non-technical and thus really
> weak argument to dismiss the list-idiomatic ninja-robot-operator (:[])
> which also happens to be shorter than the proposed alias for it. I for
> one don't see a significant benefit for adding a redundant synonym to
> `Data.List` and are thus -1 on this.
>
> > singleton :: a -> [a]
> > singleton x = [x]
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