[GHC] #8173: GHC uses nub

[GHC]

#8173: GHC uses nub
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        Reporter:  nh2               |            Owner:  leroux
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.6.3
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  Compile-time      |       Difficulty:  Moderate (less
  performance bug                    |  than a day)
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by nh2):

 Replying to [comment:9 leroux]:
 > hvr has pointed out that having cases for `[]`, `[a]`, and `[a, b]` will
 most probably prevent the overhead from using Set for trivial calls.

 Before you implement that, have you already found out why ordNub even is
 faster on singleton list? It is weird, but I am not joking: `ordNub [1]`
 is slightly faster than `nub [1]` in my Criterion benchmark.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8173#comment:10>
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