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

+1 to <$>. To me, Applicative means pure/<$>/<*>. Having 2/3rds of that in the Prelude seems weird. If we hadn't put things like *> in the Prelude, then I'd vote -1 for <$. But given the Prelude operator creep has begun, I can see why <$ lives on the other side of the line, given if I'm not particularly in favor of where the line lies. Thanks, Neil On Tue, Feb 24, 2015 at 7:06 PM, Milan Straka wrote:

Hi all,

+1 on both <$> and <$ .

Cheers, Milan Straka

...

-----Original message----- From: Edward Kmett Sent: 24 Feb 2015, 10:39

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

_______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries