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Scala:用闭包重写代码副本

closures scala

0

kiritsuku · 技术社区 · 15 年前

我有这个密码:

val arr: Array[Int] = ...
val largestIndex = {
  var i = arr.length-2
  while (arr(i) > arr(i+1)) i -= 1
  i
}
val smallestIndex = {
  var k = arr.length-1
  while (arr(largestIndex) > arr(k)) k -= 1
  k
}

def index(sub: Int, f: => Boolean): Int = {
  var i = arr.length-sub
  while (f) i -= 1
  i
}
val largest = index(2, i => arr(i) > arr(i+1))
val smallest = index(1, i => arr(largest) > arr(i))

问题是我不能在闭包中使用index()方法的参数i。有没有办法避免这个问题?

2 回复 | 直到 15 年前

1

3

Daniel C. Sobral 15 年前

val arr = Array(1,2,4,3,3,4,5)
def index(sub: Int, f: Int => Boolean): Int = {
  var i = arr.length-sub                       
  while (f(i)) i -= 1                          
  i                                            
}                                              
val largest = index(2, i => arr(i) > arr(i+1))
val smallest = index(1, i => arr(largest) > arr(i))

2

1

Randall Schulz 15 年前

val arr = Array(1,2,4,3,3,4,5)
arr: Array[Int] = Array(1, 2, 4, 3, 3, 4, 5)

scala> arr.zipWithIndex.max(Ordering.by((x: (Int, Int)) => x._1))._2
res0: Int = 6

scala> arr.zipWithIndex.min(Ordering.by((x: (Int, Int)) => x._1))._2
res1: Int = 0

或

scala> val pairOrdering = Ordering.by((x: (Int, Int)) => x._1)
pairOrdering: scala.math.Ordering[(Int, Int)] = scala.math.Ordering$$anon$4@145ad3d

scala> arr.zipWithIndex.max(pairOrdering)._2
res2: Int = 6

scala> arr.zipWithIndex.min(pairOrdering)._2
res3: Int = 0