Re: Proposal: Add conspicuously missing Functor instances for tuples

Strongly +1 from me. I very highly value instances of standard type classes for standard type constructions, particularly products, sums, and functions, not just for some library wrappers around them. And consistency usually ends up the best practical choice, whether or not many uses are clear beforehand. On Tue, Jan 19, 2016 at 6:38 AM, Edward Kmett wrote:

+1 from me.

We routinely supply instances for tuples of up to 4 or 5 elements elsewhere.

There is no need to be randomly inconsistent here.

-Edward

On Mon, Jan 18, 2016 at 3:10 PM, David Feuer wrote:

...

For some reason I really can't imagine, it seems the only tuple type with a Functor instance is (,) a. I was astonished to find that

fmap (+1) (1,2,3)

doesn't work. Since this is *useful*, and there is *only one way to do it*, I propose we add the following:

instance Functor ((,,) a b) where fmap f (a,b,c) = (a,b,f c) instance Functor ((,,,) a b c) where fmap f (a,b,c,d) = (a,b,c,f d) etc.

I would really love to see these make 8.0.0, but if that's impossible then so be it. _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

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