从范围初始化 scala BitSet [英] Initializing a scala BitSet from a range

问题描述

我想初始化一个 scala BitSet 以包含从 1 到 N 的整数.以下方法可行，但我正在寻找更好的解决方案:

I'd like to initialize a scala BitSet to contain the integers from 1 to N. The following will work, but I'm looking for a better solution:

var s = BitSet.empty ++ (1 to n)

我希望我能做这样的事情:

I was hoping that I could do something like this:

var s:BitSet = (1 to n).toSet

...但这会导致错误:

...but that results in an error:

error: polymorphic expression cannot be instantiated to expected type;
  found   : [B >: Int]scala.collection.immutable.Set[B]
  required: scala.collection.immutable.BitSet

我是否遗漏了一些明显的东西?

Am I missing something obvious?

推荐答案

这就是 breakOut 的用途:

val s: BitSet = (1 to n).map(identity)(breakOut)

请参阅这个问题以了解breakOut的内部工作原理.

See this question to understand the inner working of breakOut.

另一种解决方案是使用BitSet的构造函数:

Another solution is to use the constructor of BitSet:

val s = BitSet((1 to n): _*)

: _* 告诉编译器你想使用 Range 作为重复参数.

the : _* tells the compiler that you want to use the Range as repeated parameters.

因为 breakOut 看起来很丑，你可以使用 pimp-my-library 模式来生成更好看的代码(如 此处):

Because breakOut looks ugly you can use the pimp-my-library pattern to produce nicer looking code (as described here):

val s = (1 to n).to[BitSet]

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