Re: Proposal: Add conspicuously missing Functor instances for tuples

I share Henning's concerns. Can someone provide a realistic example of where an instance for (,,) or (,,,) *is* desirable? Tom

El 18 ene 2016, a las 15:59, Eric Seidel escribió:

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On Mon, Jan 18, 2016, at 12:44, Christopher Allen wrote: I've addressed this here:

http://bitemyapp.com/posts/2015-10-19-either-is-not-arbitrary.html

The thousand-papercuts opposition to typeclass instances on the premise that a Functor for (a, b, c) maps over the final type not making sense is a rejection of how higher kinded types and typeclasses work together. This is natural and predictable if one bothers to explain it.

The behavior is indeed predictable, but I think Henning is arguing (and I would agree) that it is *undesirable*.

That being said, I think the ship has sailed on the "should tuples be a Functor/etc" discussion. The current proposal is aimed at making the set of available instances more consistent across tuples, which I'd argue is a good thing regardless of one's position on the specific class. _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries