[Haskell-cafe] Is it acceptable if Applicative behave not like a Monad

Omari Norman omari at smileystation.com
Fri May 1 01:46:25 UTC 2015

On Thu, Apr 30, 2015 at 1:32 PM, Nikita Volkov <nikita.y.volkov at mail.ru>

> I'm afraid I have to disagree with Adam as well. Recently I've triggered a
> prolonged discussion on exactly the subject (
> https://github.com/ekmett/either/pull/38). Being originally convinced
> that the instances can behave however it fits, I think I've been
> over-persuaded in the end.
> Shortly speaking, while I can't say I like it, the rule seems to be that
> `<*>` should produce the same side effects as Monad's `ap`.
One example of a library where the Applicative and Monad instances mismatch
is uu-parsinglib.


There's a good reason the library is this way but the behavior can be
rather startling.
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