Proposal: Add a few extra members to Foldable and Traversable classes

Edward Kmett ekmett at
Fri Sep 19 21:27:02 UTC 2014

Keep in mind as part of the "burning bridges proposal that caused us to form the core libraries committee in the first place the Foldable/Traversable definitions replace the Prelude ones. There is no new conflict against Prelude.

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> On Sep 19, 2014, at 5:05 PM, Henning Thielemann <lemming at> wrote:
>> On Fri, 19 Sep 2014, David Feuer wrote:
>> Joachim, you may be right about sum and product; I really don't know. Henning: this doesn't change the Data.Foldable API at all. Data.Foldable already exports all of these functions, and the class would give each of them a valid default implementation.
> For consumers of the functions it would not change much. However, user instances with custom implementations of the new methods cannot be used with older Prelude versions anymore.
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