表达式以测试序列中的所有项是否相同

我不知道有哪种模式符合您的要求,但您可以这样做:

let allSame L =
    match L with
    | [] | [_] -> L
    | h::t when t |> List.forall ((=) h) -> L
    | _ -> failwith "unpossible!" //handle the failing match here

另外,你说的是一个序列,但你的匹配表明你正在处理一个列表。序列的对应代码如下所示

let allSameSeq s = 
    match Seq.length s with
    | 0 | 1 -> s
    | _ when Seq.skip 1 s |> Seq.forall ((=) (Seq.head s)) -> s
    | _ -> failwith "unpossible!"

请注意,此函数的性能可能比基于列表的函数差。

let (|SingleOrEmpty|AllIdentical|Neither|) (lst:'a list) =
    if lst.Length < 2 then
        SingleOrEmpty
    elif List.forall (fun elem -> elem = lst.[0]) lst then
        AllIdentical
    else
        Neither

let allElementsIdentical lst:'a list =
    match lst with
    |SingleOrEmpty|AllIdentical -> lst
    |Neither -> failwith "Not a suitable list"

我会考虑做以下的一件事:

yourSequence |> Seq.windowed(2) |> Seq.forall(fun arr -> arr.[0] = arr.[1])

let h = Seq.hd yourSequence
yourSequence |> Seq.forall((=) h)

尽可能使用库函数总是好的;)