在 F# 中迭代嵌套序列 - 如何？

发布于 2024-10-28 20:23:27 字数 608 浏览 1 评论 0原文

我可以在 F# 中定义一个简单列表，如下所示，并使用以下代码对其进行迭代：

let ar = [0;1;2;3]
ar |> Seq.iter (fun x -> printfn "Ar: %A" x)

现在考虑一个嵌套序列，如下所示：

let ar1 = [1;2;3;4]
let ar2 = [5;6;7;8]
let nested_array = [ar1; ar2]

我如何迭代此列表 - 下面的代码出现错误：

“lambda 表达式中出现意外的中缀运算符”

我在这里要做的是迭代外部序列并将其转发到第二个迭代器，然后让我访问内部数组的内容。

nested_array |>
Seq.iter (fun x -> |> 
                    Seq.iter  (fun y ->
                    printfn "Ar: %A" y))

我在这里缺少什么 - 我怀疑语法问题或（更严重/可能）缺乏 F#/FP 理解。

原文

I can define a simple list in F# as follows and iterate over it with the following code:

let ar = [0;1;2;3]
ar |> Seq.iter (fun x -> printfn "Ar: %A" x)

Now consider a nested sequence as follows:

let ar1 = [1;2;3;4]
let ar2 = [5;6;7;8]
let nested_array = [ar1; ar2]

How can I Iterate over this - the following code below gets an error:

'Unexpected infix operator in lambda expression'

What I'm trying to do here is to iterate over the outer sequence and pipe that forward to a second iterator which then lets me access the contents of the inner arrays.

nested_array |>
Seq.iter (fun x -> |> 
                    Seq.iter  (fun y ->
                    printfn "Ar: %A" y))

What am I missing here - I suspect a syntax problem or (more serious/likely) a lack of F#/FP comprehension .

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兲鉂ぱ嘚淚 2024-11-04 20:23:28

您没有使用变量x。尝试“

nested_array |> Seq.iter (fun x -> x |> Seq.iter (fun y -> printfn "Ar: %A" y))

或”（完全消除 x 的使用）

nested_array |> Seq.iter (Seq.iter (fun y -> printfn "Ar: %A" y))

或什至（也消除 y）

nested_array |> Seq.iter (Seq.iter (printfn "Ar: %A"))

You're not using your variable x. Try either

nested_array |> Seq.iter (fun x -> x |> Seq.iter (fun y -> printfn "Ar: %A" y))

or (eliminating the use of x entirely)

nested_array |> Seq.iter (Seq.iter (fun y -> printfn "Ar: %A" y))

or even (eliminating y as well)

nested_array |> Seq.iter (Seq.iter (printfn "Ar: %A"))

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丶视觉 2024-11-04 20:23:28

我通常不喜欢使用seq.iter函数，当它不在较大的处理管道的一部分中时。替代方法是仅将nested 用于：

for nested in nested_array do
  for y in nested do printfn "Ar: %A" y

尽管使用部分功能应用程序（如KVB发布）是真的，这只是个人喜好的问题 - 您期望谁阅读它。我想我的方法不是使源代码“更聪明”，如果它没有给您任何明确的价值。

I don't generally like using Seq.iter function when it is not in a part of a larger processing pipeline. The alternative is to just use nested for:

for nested in nested_array do
  for y in nested do printfn "Ar: %A" y

Although, it's true that using partial function application (as posted by kvb) nakes it quite nice, so it is just a matter of personal preference - and who you expect to read it. I guess my approach is not to make the source code "more clever" if it doesn't give you any clear value.

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