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

-1 on both. Leaving them out might encourage people to use "pure foo" or the idiom QuasiQuoter. It's not obvious [to me at least] which of the 3 styles is best, so I'd prefer to keep the additional syntax out of the Prelude. -Greg On Tue, Feb 24, 2015 at 7:43 AM, Alec wrote:

+1 on both

On Tue Feb 24 2015 at 10:42:41 AM Michael Snoyman wrote:

...

+1 on <$> +1 on <$

On Tue Feb 24 2015 at 5:39:56 PM Edward Kmett 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 _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

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