Is there a function \x -> (x, x) in standard libraries?

[Ignat Insarov]

So, it is not considered harmful. Then I propose we add it to
Data.Tuple under a humane name.

On Tue, 16 Jul 2019 at 19:41, Lennart Augustsson <lennart at augustsson.net> wrote:
>
> Or 'join (,)'
>
> On Tue, Jul 16, 2019, 09:26 Zemyla <zemyla at gmail.com> wrote:
>>
>> id &&& id
>>
>> On Tue, Jul 16, 2019, 10:58 Ignat Insarov <kindaro at gmail.com> wrote:
>>>
>>> Hello.
>>>
>>> I wonder if there is a function like \x -> (x, x) in the standard libraries.
>>>
>>> I looked up in Hoogle. It gave me links:
>>>
>>> 1. https://hackage.haskell.org/package/utility-ht/docs/Data-Tuple-HT.html#v:double
>>> 2. https://hackage.haskell.org/package/extra/docs/Data-Tuple-Extra.html#v:dupe
>>> 3. https://hackage.haskell.org/package/relude/docs/Relude-Extra-Tuple.html#v:dupe
>>>
>>> None of these is to the standard library. I wonder if there is an
>>> intentional omission for some important reason? If not, I think this
>>> function should be added to Data.Tuple.
>>>
>>> I know some of the persons that make decisions here like Category
>>> theory, so I point out this function is mentioned in Categories for
>>> the Working Mathematician, as δ, the diagonal function, on page 3
>>> (second edition), although set with angular brackets.
>>>
>>> Have a great day.
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