[Haskell-cafe] Applicative is like an Arrow

Dan Burton danburton.email at gmail.com
Fri Aug 16 21:29:40 CEST 2013

You may be interested in this paper:

Idioms are oblivious, arrows are meticulous, monads are promiscuous

"Idioms" refers to the Applicative class.

To put it briefly, if you have an instance of Arrow, you also have an
automatic instance for Applicative, which I brought up about a month ago on

-- Dan Burton

On Fri, Aug 16, 2013 at 7:52 AM, Brandon Allbery <allbery.b at gmail.com>wrote:

> On Fri, Aug 16, 2013 at 10:49 AM, Tom Ellis <
> tom-lists-haskell-cafe-2013 at jaguarpaw.co.uk> wrote:
>> On Fri, Aug 16, 2013 at 10:26:42AM -0400, Brandon Allbery wrote:
>> > My understanding is that there's a rework of Arrow in progress that may
>> > change this in the future, since *theoretical* Arrows are more distinct,
>> > flexible and useful than the current implementation.
>> I'd like to know more about that if you can provide any references.  I am
>> using
>> arrows very heavily.
> It's been mentioned (but not much more) in #haskell IRC, so I don't know
> details. I also expect it's not going to simply replace the current one, at
> least not initially; and I think it's supposed to maintain compatibility
> with the current Arrow because that's just a specialization to the function
> arrow.
> --
> brandon s allbery kf8nh                               sine nomine
> associates
> allbery.b at gmail.com
> ballbery at sinenomine.net
> unix, openafs, kerberos, infrastructure, xmonad
> http://sinenomine.net
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