Arrows that are also Functors
Maciej Marcin Piechotka
uzytkownik2 at gmail.com
Tue Apr 19 18:22:39 CEST 2011
On Tue, 2011-04-19 at 17:29 +0200, Henning Thielemann wrote:
> Is it common to make a type an instance of both Arrow and Functor type
> class? If a type is both instance of Arrow and Functor, would you expect
> that fmap = (^<<) ? If yes, how about adding this as expected law to the
> Control.Arrow documentation? Same question for Applicative functors and
> liftA2 (,) = (&&&). (Btw. Control.Arrow haddock documentation does not
> mention any Arrow law so far.)
I believe reading in some paper/monad reader article that Arrow is
equivalent to Category that is Functor.
In any case iff there have been instances I would expect such things (I
believe both are true for (->)).
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