[Haskell-cafe] Unit and pair

MigMit miguelimo38 at yandex.ru
Tue May 8 19:49:41 CEST 2012

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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