Proposal: Add (<$>) to Prelude as part of the AMP in GHC 7.10-RC3

[Conal Elliott]

(<$>): +1
(<$): +1


On Tue, Feb 24, 2015 at 7:39 AM, Edward Kmett <ekmett at gmail.com> wrote:

> We have a couple of weeks until the third release candidate for GHC 7.10
> goes out the door.
>
> Along the way with the last couple of release candidates folks have found
> some problems with the way we implemented the AMP. [1][2]
>
> Most notably, we failed to include (<$>) in the Prelude, so the standard
> idiom of
>
> foo <$> bar <*> baz <*> quux
>
> doesn't work out of the box!
>
> I'd like to include (<$>) in the Prelude in RC3.
>
> I'd also like to invite discussion about whether folks believe we should
> include (<$) out of the box.
>
> (<$) has been a member of Functor for a long time, which is only visible
> if you import it from Data.Functor or bring in Control.Applicative. There
> is an idiom that you use (<*) and (<$) to point to the parts of the
> structure that you want to keep the answers from when building longer such
> Applicative chains.
>
> Discussion Period: 2 weeks
>
> Thank you,
> -Edward Kmett
>
> [1]
> http://www.reddit.com/r/haskell/comments/2wzixa/shouldnt_be_in_prelude/
> [2] https://plus.google.com/115504368969270249241/posts/URzeDWd7qMp
>
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