[GHC] #9586: Implement Traversable/Foldable-Burning-Bridges Proposal

[GHC]

#9586: Implement Traversable/Foldable-Burning-Bridges Proposal
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              Reporter:  hvr         |            Owner:  hvr
                  Type:  task        |           Status:  new
              Priority:  normal      |        Milestone:  7.10.1
             Component:              |          Version:
  libraries/base                     |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Difficult (2-5
  Unknown/Multiple                   |  days)
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:  Phab:D209   |
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Comment (by Herbert Valerio Riedel <hvr@…>):

 In [changeset:"1812898c0332c6807201938911bb914633267d9d/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="1812898c0332c6807201938911bb914633267d9d"
 Turn a few existing folds into `Foldable`-methods (#9621)

 Turn `toList`, `elem`, `sum`, `product`, `maximum`, and `minimum` into
 `Foldable` methods. This helps avoiding regressions (and semantic
 differences) while implementing #9586

 Reviewed By: austin, dfeuer, ekmett

 Differential Revision: https://phabricator.haskell.org/D231
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9586#comment:13>
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