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

[Zemyla]

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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