Deprecate Foldable for Either

amindfv at amindfv at
Sat Mar 18 21:25:47 UTC 2017

The issue is that if a "grumpy person" imports any library which uses the Prelude (I have a feeling they might), then under the open world assumption they will get the instances that to them are broken.

If we can get a warning then those of us who find the instances dangerous might be more willing to live and let live.


> El 18 mar 2017, a las 14:21, Carter Schonwald <carter.schonwald at> escribió:
> for what?
> lets just have a learners / grumpy people prelude
>> On Fri, Mar 17, 2017 at 8:31 AM, Henning Thielemann <lemming at> wrote:
>> On Fri, 3 Mar 2017, Ivan Lazar Miljenovic wrote:
>>>> On 3 March 2017 at 06:28, David Feuer <david.feuer at> wrote:
>>>> Yes. That is an excellent plan. I'd love to call it Data.List, but others
>>>> will disagree.
>>> Same here.
>>> I wasn't that happy with the FTP proposal when it first came up due to
>>> potential confusions (primarily due to naming conventions like
>>> "length"), but now that it's done we shouldn't go back.
>> We should have at least compiler warnings for those who care.
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