Scala函数综合

一 需求

 

 

二 代码

object sumfunc {  def sum(f:Int => Int)(a:Int)(b:Int):Int ={  @annotation.tailrec  def loop(n:Int,acc:Int):Int={  if(n>b){  println(s"n=${n},acc=${acc}")  acc  }else{  println(s"n=${n},acc=${acc}")  loop(n+1,acc+f(n))  }  }  loop(a,0)  }                                               //> sum: (f: Int => Int)(a: Int)(b: Int)Int  sum(x =>x)(1)(5)                                //> n=1,acc=0                                                  //| n=2,acc=1                                                  //| n=3,acc=3                                                  //| n=4,acc=6                                                  //| n=5,acc=10                                                  //| n=6,acc=15                                                  //| res0: Int = 15    sum(x =>x*x)(1)(5)                              //> n=1,acc=0                                                  //| n=2,acc=1                                                  //| n=3,acc=5                                                  //| n=4,acc=14                                                  //| n=5,acc=30                                                  //| n=6,acc=55                                                  //| res1: Int = 55  sum(x =>x*x*x)(1)(5)                            //> n=1,acc=0                                                  //| n=2,acc=1                                                  //| n=3,acc=9                                                  //| n=4,acc=36                                                  //| n=5,acc=100                                                  //| n=6,acc=225                                                  //| res2: Int = 225    val sum1=sum(x =>x*x)_                          //> sum1  : Int => (Int => Int) = sumfunc$$$Lambda$13/757108857@6bdf28bb  sum1(1)(5)                                      //> n=1,acc=0                                                  //| n=2,acc=1                                                  //| n=3,acc=5                                                  //| n=4,acc=14                                                  //| n=5,acc=30                                                  //| n=6,acc=55                                                  //| res3: Int = 55}