[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 request   |               Status:  new
        Priority:  low               |            Milestone:
       Component:  libraries/base    |              Version:
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by wizzup):

 On a side note; the `Data.List.Split` use `On` with different meaning.

 There should not be inconsistency in `Data.List` and `Data.List.Split`.

 {{{
 > splitOn "x" "axbxc"
 ["a","b","c"]

 > splitOn "x" "axbxcx"
 ["a","b","c",""]

 > splitWhen (<0) [1,3,-4,5,7,-9,0,2]
 [[1,3],[5,7],[0,2]]
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12868#comment:3>
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