f# - 具有重复元素的无限序列

Question

我需要创建一个无限序列，其中包含无限重复的元素子序列。

[1; 2; 3; 4; 1; 2; 3; 4; 1; 2; 3; 4; ...]

所以我写了这个:

let l = [1; 2; 3; 4]
let s = seq { while true do yield! l }

有没有标准的方法(功能)来做到这一点？

Answer 1

类似于丹尼尔的答案，但将其封装成一个函数，并假装该函数在 Seq 模块中:

module Seq =
    let infiniteOf repeatedList = 
        Seq.initInfinite (fun _ -> repeatedList) 
        |> Seq.concat

// Tests
let intList = [1; 2; 3; 4]
let charList = ['a'; 'b'; 'c'; 'd']
let objList = [(new System.Object()); (new System.Object()); (new System.Object()); (new System.Object())]
do
    Seq.infiniteOf intList |> Seq.take 20 |> Seq.iter (fun item -> printfn "%A" item)
    Seq.infiniteOf charList |> Seq.take 20 |> Seq.iter (fun item -> printfn "%A" item)
    Seq.infiniteOf objList |> Seq.take 20 |> Seq.iter (fun item -> printfn "%A" item)