scala高阶函数

import scala.math._

object Test extends App {
  //scala中函数是头等公民，可以像其他类型一样被传递
  val num = 3.14
  val fun: Double => Double = ceil _ //将ceil方法转成函数

  //调用函数
  println(fun(4))
  //传递给其他函数
  val a = Array(3.14,1.42,2.5).map(fun)

}

object Test extends App {
  //匿名函数
  val fun1 = (x: Double) => x * 3

  def fun2(x: Double) = {
    x * 3
  }

}

import scala.math._

object Test extends App {

  def valueAtOneQuarter(num: Double, f: Double => Double) = {
    f(num)
  }

  val result = valueAtOneQuarter(25, ceil _)
  println(result)


  val a: (Double, Double => Double) => Double = valueAtOneQuarter _
  //函数类型 (Double, Double => Double) => Double

  //函数产出函数
  def mulBy(factor:Double) = {
    (x:Double)=>x*3
  }

  val b: Double => Double => Double = mulBy _

}