Scala 练习2

Scala

the more you know about scala type system, the more you can give the scala compiler.

package student.scala
import scala.reflect.ClassTag
object Execise2 extends App {
  //1 def foo (msg:String) = println(msg)
  //改造上面的这个函数，使其可以输出
  //foo(100) foo(List(1,2,3) 
  // foo(Array(1,2,3) :Array[1,2,3]
  def foo(msg:String) = println(msg)
  foo("abc")
  def foo2[T](msg:T) = msg match { case a:Array[_]=> println("Array[" + a.mkString(",") + "]")  ;case _=> println(msg.toString()) }
  foo2(List(1,2,3))
  foo2(100)
  foo2(Array(1,2,3))
  //2 写一个泛型函数，接受一个Array,
  //然后返回一个仅包含原数组第一个元素的新数组
  def first[T:ClassTag](a:Array[T]) = Array(a(0))
  println(first(Array(1,2,3)).mkString(""))
}