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
}