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

On Thu, Apr 30, 2015 at 1:32 PM, Nikita Volkov wrote:

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. http://stackoverflow.com/questions/18275123/cannot-compute-minimal-length-of... There's a good reason the library is this way but the behavior can be rather startling.