instance Applicative Data.Map

Edward Kmett ekmett at
Thu Nov 15 15:10:29 CET 2012

There is also Data.Functor.Bind which provides a 'semimonad' (perhaps that
would have been a better name) for Map and other types that can't offer
'pure' as well.

The originally were added because many comonads cannot offer an identity to
their apply-like operation, but then we started finding more
semiapplicatives and semimonads that weren't comonadic, like Map, etc.

I think Daniel Peebles was the first to spot the Bind instance for Map, and
by extension the Apply instance.

On Thu, Nov 15, 2012 at 4:19 AM, Henning Thielemann <
lemming at> wrote:

> On Wed, 14 Nov 2012, Brent Yorgey wrote:
>  Precisely.  See edwardk's package
>> which defines this and many other related things.
> I see, what I need is the Apply class from that package. Fortunately
> Data.Map is already an instance of the Apply class.
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