[GHC] #12868: Add groupOn function to Data.List

[GHC]

#12868: Add groupOn function to Data.List
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           Reporter:  wizzup         |             Owner:
               Type:  feature        |            Status:  new
  request                            |
           Priority:  low            |         Milestone:
          Component:                 |           Version:
  libraries/base                     |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 sortOn was already add in #9004 but what about groupOn ?

 According to
 https://wiki.haskell.org/List_function_suggestions#groupOn_and_sortOn both
 functions are "so common".

 Although rejected in #2659, this might be a good time to reconsider.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12868>
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