Scala 中的无限流 [英] Infinite streams in Scala

问题描述

说我有一个功能，例如老最爱

Say I have a function, for example the old favourite

def factorial(n:Int) = (BigInt(1) /: (1 to n)) (_*_)

现在我想找到 factorial(n) 适合 Long 的 n 的最大值.我可以做

Now I want to find the biggest value of n for which factorial(n) fits in a Long. I could do

(1 to 100) takeWhile (factorial(_) <= Long.MaxValue) last

这是可行的，但 100 是一个任意的大数；在左侧，我真正想要的是一个无限流，它不断生成更高的数字，直到满足 takeWhile 条件.

This works, but the 100 is an arbitrary large number; what I really want on the left hand side is an infinite stream that keeps generating higher numbers until the takeWhile condition is met.

我想出了

val s = Stream.continually(1).zipWithIndex.map(p => p._1 + p._2)

但是有更好的方法吗?

(我也知道我可以递归地得到一个解决方案，但这不是我想要的.)

(I'm also aware I could get a solution recursively but that's not what I'm looking for.)

推荐答案

Stream.from(1)

创建一个从 1 开始递增 1 的流.它都在 API 文档.

creates a stream starting from 1 and incrementing by 1. It's all in the API docs.

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