对于可能为空的 Seq，使用 Option[T] 的最小值/最大值? [英] Min/max with Option[T] for possibly empty Seq?

问题描述

我正在做一些 Scala 体操，其中我有 Seq[T]，我试图在其中找到最小"元素.这就是我现在所做的:

I'm doing a bit of Scala gymnastics where I have Seq[T] in which I try to find the "smallest" element. This is what I do right now:

val leastOrNone = seq.reduceOption { (best, current) =>
    if (current.something < best.something) current
    else best
}

它工作得很好，但我不太满意 - 这么简单的事情有点长，而且我不不太关心如果".使用 minBy 会更优雅:

It works fine, but I'm not quite satisfied - it's a bit long for such a simple thing, and I don't care much for "if"s. Using minBy would be much more elegant:

val least = seq.minBy(_.something)

... 但是 min 和 minBy 在序列为空时抛出异常.是否有一种惯用的、更优雅的方式来查找可能为空的列表的最小元素作为 Option?

... but min and minBy throw exceptions when the sequence is empty. Is there an idiomatic, more elegant way of finding the smallest element of a possibly empty list as an Option?

推荐答案

Starting Scala 2.13, minByOption/maxByOption 现在是标准库的一部分，如果序列为空，则返回 None:

Starting Scala 2.13, minByOption/maxByOption is now part of the standard library and returns None if the sequence is empty:

seq.minByOption(_.something)

List((3, 'a'), (1, 'b'), (5, 'c')).minByOption(_._1) // Option[(Int, Char)] = Some((1,b))
List[(Int, Char)]().minByOption(_._1)                // Option[(Int, Char)] = None

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