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

[Ross Paterson]

On Thu, Apr 30, 2015 at 10:11:49PM -0700, Andrew Gibiansky wrote:
> I agree that, now that we have AMP, applicative and monadic interfaces
> absolutely *should* match, and that it should be considered an error for them
> not to; semantically different interfaces can be provided with newtypes.

This requirement is in the documentation for both Applicative and Monad
classes.  (It's been in Applicative since 2010, and was added to Monad
in the AMP release.)