更新序列中的多个值 [英] Update multiple values in a sequence

问题描述

要获得一个更新了一个值的序列，可以使用

To get a sequence with one value updated, one can use

seq.updated(index, value)

我想为一系列元素设置一个新值.有图书馆功能吗?我目前使用以下功能:

I want to set a new value for a range of elements. Is there a library function for that? I currently use the following function:

def updatedSlice[A](seq: List[A], ind: Iterable[Int], value: A): List[A] = 
    if (ind.isEmpty) seq
    else updatedSlice(seq.updated(ind.head, value), ind.tail, value)

除了需要编写函数外，这似乎效率低下，并且仅适用于列表，而不适用于 Seq 和 String 的任意子类.所以，

Besides the need of writing function, this seems to be inefficient, and also works only for lists, rather than arbitrary subclasses of Seq and Strings. So,

• 有执行它的方法吗?
• 如何对函数进行参数化以获取(并返回) Seq [A] 的某些子类?

• is there a method that performs it?
• how can I parametrize the function to take (and return) some subclass of Seq[A]?

推荐答案

在计算机上没有人说过:

No one at a computer has said:

scala> (1 to 10).toSeq patch (3, (1 to 5), 3)
res0: scala.collection.immutable.IndexedSeq[Int] = Vector(1, 2, 3, 1, 2, 3, 4, 5, 7, 8, 9, 10)

保存@Marth的绿色支票.

Save your green checks for @Marth.

请注意，他们仍在努力.

Note they're still working on it.

https://issues.scala-lang.org/browse/SI-8474

关于不经常使用的API的一些看法.

Which says something about less-frequently-used API.

更新:我第二次看了这个问题，发现我读错了，哦:

Update: I glanced at the question a second time and saw that I misread it, oh well:

scala> implicit class x[A](as: Seq[A]) {
     | def updatedAt(is: collection.Traversable[Int], a: A) = {
     | (as /: is) { case (xx, i) => xx updated (i, a) } } }
defined class x

scala> (1 to 10) updatedAt (Seq(3,6,9), 0)
res9: Seq[Int] = Vector(1, 2, 3, 0, 5, 6, 0, 8, 9, 0)

打一场轻松的高尔夫球.

Just a relaxing round of golf.

更新:s/放松/烦人

看起来它需要更多类型参数，但是我没有时间限制.

Looks like it needs more type params, but I don't have a time slice for it.

scala> implicit class slicer[A, B[_] <: Seq[_]](as: B[A]) {
     | def updatedAt[That<:B[_]](is: Traversable[Int], a: A)(implicit cbf: CanBuildFrom[B[A], A, That]) =
     | (as /: is) { case (x,i) => x updated[A,That] (i,a) }}
<console>:15: error: type arguments [A,That] conform to the bounds of none of the overloaded alternatives of
 value updated: [B >: _$1, That](index: Int, elem: B)(implicit bf: scala.collection.generic.CanBuildFrom[Seq[_$1],B,That])That <and> [B >: A, That](index: Int, elem: B)(implicit bf: scala.collection.generic.CanBuildFrom[Repr,B,That])That
       (as /: is) { case (x,i) => x updated[A,That] (i,a) }}
                                    ^

谁甚至知道更新已超载?

Who even knew updated was overloaded?

我最喜欢的奥德斯基语录:

My new favorite Odersky quote:

我一直玩到它变得太乏味为止.

I played with it until it got too tedious.

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