Scala 中最优雅的重复循环
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Most elegant repeat loop in Scala
提问by Przemek
I'm looking for an equivalent of:
我正在寻找相当于：
for(_ <- 1 to n)
some.code()
that would be shortest and most elegant. Isn't there in Scala anything similar to this?
那将是最短和最优雅的。Scala 中没有类似的东西吗？
rep(n)
some.code()
This is one of the most common constructs after all.
毕竟，这是最常见的构造之一。
PS
聚苯乙烯
I know it's easy to implement rep, but I'm looking for something predefined.
我知道实现 rep 很容易，但我正在寻找预定义的东西。
回答by Daniel C. Sobral
1 to n foreach { _ => some.code() }
回答by kiritsuku
You can create a helper method
您可以创建一个辅助方法
def rep[A](n: Int)(f: => A) { if (n > 0) { f; rep(n-1)(f) } }
and use it:
并使用它：
rep(5) { println("hi") }
Based on @J?rgs comment I have written such a times-method:
基于@J?rgs 评论，我写了这样一个时间方法：
class Rep(n: Int) {
def times[A](f: => A) { loop(f, n) }
private def loop[A](f: => A, n: Int) { if (n > 0) { f; loop(f, n-1) } }
}
implicit def int2Rep(i: Int): Rep = new Rep(i)
// use it with
10.times { println("hi") }
Based on @DanGordon comments, I have written such a times-method:
根据@DanGordon 的评论，我写了这样一个时间方法：
implicit class Rep(n: Int) {
def times[A](f: => A) { 1 to n foreach(_ => f) }
}
// use it with
10.times { println("hi") }
回答by Landei
I would suggest something like this:
我会建议这样的事情：
List.fill(10)(println("hi"))
There are other ways, e.g.:
还有其他方法，例如：
(1 to 10).foreach(_ => println("hi"))
Thanks to Daniel S. for the correction.
感谢 Daniel S. 的更正。
回答by missingfaktor
With scalaz 6:
使用 scalaz 6：
scala> import scalaz._; import Scalaz._; import effects._;
import scalaz._
import Scalaz._
import effects._
scala> 5 times "foo"
res0: java.lang.String = foofoofoofoofoo
scala> 5 times List(1,2)
res1: List[Int] = List(1, 2, 1, 2, 1, 2, 1, 2, 1, 2)
scala> 5 times 10
res2: Int = 50
scala> 5 times ((x: Int) => x + 1).endo
res3: scalaz.Endo[Int] = <function1>
scala> res3(10)
res4: Int = 15
scala> 5 times putStrLn("Hello, World!")
res5: scalaz.effects.IO[Unit] = scalaz.effects.IO$$anon@36659c23
scala> res5.unsafePerformIO
Hello, World!
Hello, World!
Hello, World!
Hello, World!
Hello, World!
[ Snippet copied from here.]
