f# - 将数组映射到上一个、当前和下一个值的元组数组

Question

映射以下内容的最佳方式是什么:

[|"A"; "B"; "C"; "D"|]

到

[|("","A","B"); ("A","B","C"); ("B","C","D"); ("C","D","")|]

?

Answer 1

我更喜欢基于惯用组合器的方法:在数组的两端附加一个空字符串，使用 Seq.windowed 3生成三个项目的滑动数组序列，最后将每个序列元素映射到元组并将序列转换回数组:

let conv source =
    Array.concat [[|String.Empty|]; source; [|String.Empty|]] |> Seq.windowed 3
    |> Seq.map (fun x -> x.[0],x.[1],x.[2]) |> Seq.toArray

在 FSI 下测试 conv [|"A";"B";"C";"D"|] 产生:

val it : (string * string * string) [] =
  [|("", "A", "B"); ("A", "B", "C"); ("B", "C", "D"); ("C", "D", "")|]