leftToMaybe/rightToMaybe

[Jon Fairbairn]

"wren ng thornton" <wren at freegeek.org> writes:

> On 8/9/13 2:52 AM, Andreas Abel wrote:
>> I bet that most imports of Control.Arrow are to make up for an
>> impoverished Data.Tuple, and proper arrow programming is the exception.
>
> I, for one, exclusively use the main arrow combinators[1] at (->) for the
> purpose of manipulating co/products in the obvious categorical way.
>
> The only time I'd use any other instance of Arrow/ArrowChoice is if that's
> the API some library gives me. I'd certainly never define my own instances
> because the Arrow class is IMO fundamentally broken. The presence of the
> arr method requires that *all* Haskell functions can be embedded into your
> category, which makes Arrows unsuitable for any of the subcategories or
> DSLs I happen to care about.

+1

> I know there are some folks who are really attached to Arrows, but I'd
> much rather see Arrow/ArrowChoice abandoned in favor of extending Category
> to have subclasses for categories with co/products.
>
>
> [1] first, second, (&&&), (***), left, right, (|||), (+++)

-- 
Jón Fairbairn                                 Jon.Fairbairn at cl.cam.ac.uk