object test {

     //一个参数列表，3个参数

  def sum(a: Int, b: Int, c: Int) = a + b + c     //> sum: (a: Int, b: Int, c: Int)Int

  //将一个参数列表，拆分成三个参数列表

  def sum4(a: Int)(b: Int)(c: Int) =  a + b + c   //> sum4: (a: Int)(b: Int)(c: Int)Int

  //sum4的偏应用函数

  val fn4 = sum4 _                                //> fn4  : Int => (Int => (Int => Int)) = <function1>

    //根据偏应用函数，便可定义出如下函数：

  def sum44(a: Int) = {

    (b: Int) =>

      {

        (c: Int) =>

          {

            a + b + c

          }

      }

  }                                               //> sum44: (a: Int)Int => (Int => Int)

  //自定义函数的偏应用函数

  val fn44 = sum44 _                              //> fn44  : Int => (Int => (Int => Int)) = <function1>

  sum(1, 2, 3)                                    //> res0: Int = 6

  sum4(1)(2)(3)                                   //> res1: Int = 6

  sum44(1)(2)(3)                                  //> res2: Int = 6

  //将2,3分别偏应用到第一个，第二个参数上

  val fn44_2 = sum44(2)(3)(_:Int)                 //> fn44_2  : Int => Int = <function1>

  fn44_2(4)                                       //> res3: Int = 9

  fn44_2.apply(4)                                 //> res4: Int = 9

}