"wren ng thornton" 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@cl.cam.ac.uk