[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:  #9621
             Test Case:              |
              Blocking:              |
Differential Revisions:  Phab:D209   |
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Changes (by hvr):

 * related:   => #9621


Comment:

 Replying to [comment:5 dfeuer]:
 > rwbarton points out that there are optimized versions of these for
 various things, and that most containers use `size` instead of `length`.
 Therefore, I would propose instead adding `size` and `null` to the
 `Foldable` class, with default definitions as above.

 Extending `Foldable` has become a ticket of its own at #9621

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9586#comment:15>
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