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Herbert Valerio Riedel authored
This was dropped last-minute from d94de872 (re #4834) together with the default implementation for `(>>)` (see 65f887e1 for explanation). However, the risk of accidental mutually recursive definitions of `return`/`pure` is rather low as unlike with the `(>>) = (*>)` default, any cyclic definitions would necessarily wind up being new ones, rather than changing the semantics for old operations and introducing bottoms. On the other hand, not having the default method implementation in place in GHC 7.10 would complicate/delay any future attempt to clean-up the `Monad`-class. This finally allows (for `base >= 4.8`) to define a F/A/M instance-chain with the following minimal definitions (while ignoring that `return` is still a class-method in `Monad`) instance Functor M where fmap = ... instance Applicative M where pure = ... (<*>) = ... instance Monad M where (>>=) = ... Reviewed By: ekmett, austin Differential Revision: https://phabricator.haskell.org/D647
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