[GHC] #4282: Data.List.intersperse not lazy enough

[GHC]

#4282: Data.List.intersperse not lazy enough
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    Reporter:  daniel.is.fischer  |       Owner:                       
        Type:  proposal           |      Status:  new                  
    Priority:  normal             |   Component:  libraries/base       
     Version:  6.12.3             |    Keywords:  intersperse, laziness
    Testcase:                     |   Blockedby:                       
          Os:  Unknown/Multiple   |    Blocking:                       
Architecture:  Unknown/Multiple   |     Failure:  Other                
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Comment(by duncan):

 See the strictness testing framework in the stream fusion list library. It
 has a test that identifies this and a few other similar cases. I recall
 that there are two where the base implementations are too strict,
 intersperse and intercalate. There are others where H98 is basically wrong
 and base is right. There's particular wierdness with some of the generic
 functions not matching strictness with the non-generic versions.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4282#comment:1>
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