[英]Get first n elements from List
我有一個List
val family=List("1","2","11","12","21","22","31","33","41","44","51","55")
我想采取它的前n個元素,但問題是parents
大小不固定。
val familliar=List("1","2","11") //n=3
你可以使用take
scala> val list = List(1,2,3,4,5,6,7,8,9)
list: List[Int] = List(1, 2, 3, 4, 5, 6, 7, 8, 9)
scala> list.take(3)
res0: List[Int] = List(1, 2, 3)
List(1,2,3).take(100) //List(1,2,3)
take的簽名會將參數與index進行比較,因此增量索引永遠不會超過參數
采取的簽名
override def take(n: Int): List[A] = {
val b = new ListBuffer[A]
var i = 0
var these = this
while (!these.isEmpty && i < n) {
i += 1
b += these.head
these = these.tail
}
if (these.isEmpty) this
else b.toList
}
使用take
:
val familliar = family.take(3)
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