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From aarondav <...@git.apache.org>
Subject [GitHub] incubator-spark pull request: Add subtractByKey to the JavaPairRDD...
Date Sun, 16 Feb 2014 19:07:06 GMT
Github user aarondav commented on the pull request:

    https://github.com/apache/incubator-spark/pull/600#issuecomment-35207151
  
    CC @pwendell and @JoshRosen 
    
    This looks good to me in that it should work in the style elsewhere in this file, but
I have a question for someone more knowledgeable with this area of the code than I. This line
of code (used analogously throughout this file):
    
    `implicit val cmw: ClassTag[W] = implicitly[ClassTag[AnyRef]].asInstanceOf[ClassTag[W]]`
    
    doesn't actually get a ClassTag[W], it just gets ClassTag.AnyRef and dresses it up like
one. If any of the Scala APIs really needed W's ClassTag, they would fail. But AnyRef can
make a poor approximation of W for creating stuff like Arrays, which can certainly hold W's,
but also anything else. Are we just lucky that this works right now, or is there a deeper
reason for why this is a good idea?


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