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How to get a set of elements in a list based on the index of an element in Scala?

I have one list and the other list contains the index I am interested in. For example,

val a=List("a","b","c","d")
val b=List(2,3)

Then I need to return a list with the value List ("b", "c"), since List (2,3) said I like to take the 2nd and 3rd elements from element "a". How to do it?

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3 answers 


val results = b.map(i => a(i - 1))


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I like the order of my expressions in the code to reflect the order of evaluation, so I like to use the scalaz operator for this type |> 

b.map(_ - 1 |> a)


This is especially true when you are used to writing bash scripts.

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Consider this method apply

, which checks (avoids) possible IndexOutOfBoundsException

,

implicit class FetchList[A](val in: List[A]) extends AnyVal { 
  def apply (idx: List[Int]) = for (i <- idx if i < in.size) yield in(i-1) 
}

Thus,

a(b)
res: List[String] = List(b, c)
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