获取数组，列表或序列的第N个元素的不同参数顺序

问题描述

在获取Array，List或Seq的第N个元素的函数中是否有不同的参数顺序是有充分的理由的?

Is there a good reason for a different argument order in functions getting N-th element of Array, List or Seq:

Array.get source index
List .nth source index
Seq  .nth index  source

我想使用管道运算符，似乎只有在Seq中才有可能:

I would like to use pipe operator and it seems possible only with Seq:

s |> Seq.nth n

是否可以对Array或List使用相同的符号?

Is there a way to have the same notation with Array or List?

推荐答案

我认为没有任何好的理由来定义Array.get和List.nth.鉴于流水线在F#中非常常见，因此应该定义流水线，以使source参数排在最后.

I don't think of any good reason to define Array.get and List.nth this way. Given that pipeplining is very common in F#, they should have been defined so that the source argument came last.

对于List.nth，它变化不大，因为您可以使用Seq.nth，并且时间复杂度仍然为O(n)，其中n是列表的长度:

In case of List.nth, it doesn't change much because you can use Seq.nth and time complexity is still O(n) where n is length of the list:

[1..100] |> Seq.nth 10

在阵列上使用Seq.nth并不是一个好主意，因为您会丢失随机访问权限.要使O(1)的运行时间保持为Array.get，您可以定义:

It's not a good idea to use Seq.nth on arrays because you lose random access. To keep O(1) running time of Array.get, you can define:

[<RequireQualifiedAccess>]
module Array =
    /// Get n-th element of an array in O(1) running time
    let inline nth index source = Array.get source index

通常，可以使用flip函数减轻不同的参数顺序:

In general, different argument order can be alleviated by using flip function:

let inline flip f x y = f y x

您可以直接在上面的功能上使用它:

You can use it directly on the functions above:

[1..100] |> flip List.nth 10
[|1..100|] |> flip Array.get 10

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