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IterableLike should override toIterator to not use toStream #4802

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scabug opened this issue Jul 14, 2011 · 2 comments
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IterableLike should override toIterator to not use toStream #4802

scabug opened this issue Jul 14, 2011 · 2 comments
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@scabug
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@scabug scabug commented Jul 14, 2011

(Gen)TraversableOnce.toIterator is overridden in TraversableLike as {toStream.iterator}. But for Iterables, this should just be {iterator}.

Should be easy win, but as a motivator example, the following is inefficient (due to the intermediate Stream):

def izip[A,B](xs: TraversableOnce[A], ys: TraversableOnce[B]) =
  xs.toIterator zip ys.toIterator

and must be expanded to:

def izip[A,B](xs: Iterable[A], ys: Iterable[B]) =
  xs.iterator zip ys.iterator
def izip[A,B](xs: Iterator[A], ys: Iterable[B]) =
  xs zip ys.iterator
def izip[A,B](xs: Iterable[A], ys: Iterator[B]) =
  xs.iterator zip ys
def izip[A,B](xs: Iterator[A], ys: Iterator[B]) =
  xs zip ys
// .. and more needed to handle Traversables as well
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@scabug scabug commented Jul 14, 2011

Imported From: https://issues.scala-lang.org/browse/SI-4802?orig=1
Reporter: Yang Zhang (yaaang)
Affected Versions: 2.9.0

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@scabug scabug commented Jul 16, 2011

Commit Message Bot (anonymous) said:
(extempore in r25302) Make IterableLike.toIterator more efficient

Override TraversableLike.toIterator which uses unnecessary toStream.

Fixes #4802. Contributed by Yang Zhang.

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