[Haskell-cafe] Unit and pair

[Tony Morris]

On 09/05/12 03:49, MigMit wrote:
> On 8 May 2012, at 21:42, Felipe Almeida Lessa wrote:
>
>> On Tue, May 8, 2012 at 2:36 PM, MigMit <miguelimo38 at yandex.ru> wrote:
>>> Hi café, a quick question.
>>>
>>> Is there a somewhat standard class like this:
>>>
>>> class Something c where
>>>    unit :: c () ()
>>>    pair :: c x y -> c u v -> c (x, u) (y, v)
>>>
>>> ?
>>>
>>> I'm using it heavily in my current project, but I don't want to repeat somebody else's work, and it seems general enough to be defined somewhere; but my quick search on Hackage didn't reveal anything.
>>>
>>> I know about arrows; this, however, is something more general, and it's instances aren't always arrows.
>> Are you aware of generalized arrows [1]? It's still a lot more than
>> your Something, though.
> I've heard of them, but some instances of my Something class aren't categories either, which rules out GArrows too.
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data-lens has something similar (Tensor):

http://hackage.haskell.org/packages/archive/data-lens/2.10.0/doc/html/Control-Category-Product.html

-- 
Tony Morris
http://tmorris.net/