Merging streams in scala
我需要帮助将两个流合并为一个。输出必须如下：
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| (elem1list1#elem1list2, elem2list1#elem2list2...) |
，如果任何流为空，该函数就会中断
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| def mergeStream (a : Stream [A ], b : Stream [A ]):Stream [A ] =
if (a. isEmpty || b. isEmpty) Nil
else (a,b ) match {
case(x #::xs, y #::ys ) => x #::y
} |
有什么提示如何解决？
您可以使用scalaz中的交错：
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| scala> (Stream(1,2) interleave Stream.from(10)).take(10).force
res1: scala.collection.immutable.Stream[Int] = Stream(1, 10, 2, 11, 12, 13, 14, 15, 16, 17) |
您也可以将两个Stream一起zip一起使用，这将截断较长的Stream，并将它们从元组中删除flatMap：
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| a. zip(b ). flatMap { case (a, b ) => Stream (a, b ) } |
尽管我不能说它的效率。
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| scala > val a = Stream (1, 2, 3, 4)
a : scala. collection. immutable. Stream[Int ] = Stream (1, ?)
scala > val b = Stream. from(3)
b : scala. collection. immutable. Stream[Int ] = Stream (3, ?)
scala > val c = a. zip(b ). flatMap { case (a, b ) => Stream (a, b ) }. take(10). toList
c : List [Int ] = List (1, 3, 2, 4, 3, 5, 4, 6) |
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| def mergeStream (s1 : Stream [Int ], s2 : Stream [Int ]): Stream [Int ] = (s1, s2 ) match {
case (x #::xs, y #::ys ) => x #:: y #:: mergeStream (xs, ys )
case _ => Stream. empty
}
scala > mergeStream (Stream. from(1), Stream. from(100)). take(10). toList
res0 : List [Int ] = List (1, 100, 2, 101, 3, 102, 4, 103, 5, 104) |