How can I initialize array with type A to have same length as other array? (in this case A is either String or Int)
def init_arr_with_same_len[A](arr1: Array[A]): Array[A] = {
val len = arr1.length
val arr2 = new Array[A](len)
arr2
}
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2 Answers
Arrays are something a little bit special when compared to other collection types. See this lovely article for more details (http://docs.scala-lang.org/overviews/collections/arrays.html).
The short of it is in order for Arrays in scala to support generics (which java arrays do not), you need to provide a scala.reflect.ClassTag for the generic type.
Welcome to Scala version 2.11.7 (OpenJDK 64-Bit Server VM, Java 1.8.0_65).
Type in expressions to have them evaluated.
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scala> import scala.reflect.ClassTag
import scala.reflect.ClassTag
scala> def arrayOfSameTypeAndSize[A](a: Array[A])(implicit ct: ClassTag[A]): Array[A] = new Array(a.size)
arrayOfSameTypeAndSize: [A](a: Array[A])(implicit ct: scala.reflect.ClassTag[A])Array[A]
scala> val x: Array[Int] = arrayOfSameTypeAndSize(Array(1,2,3))
x: Array[Int] = Array(0, 0, 0)
scala>
Or slightly more succinctly.
scala> def arrayOfSameTypeAndSize[A: ClassTag](a: Array[A]): Array[A] = new Array(a.size)
arrayOfSameTypeAndSize: [A](a: Array[A])(implicit evidence$1: scala.reflect.ClassTag[A])Array[A]
scala> val x: Array[Int] = arrayOfSameTypeAndSize(Array(1,2,3))
x: Array[Int] = Array(0, 0, 0)
scala>
Comments
You're looking for Array#clone.
