F#中类型的最大/最小值

Question

Unchecked.defaultof<'T>为任何类型生成默认值.是否存在这样的通用函数来为具有最大/最小值的类型有意义的任何类型生成最大/最小值？

编辑

回答John Palmer关于我认为它有用的问题:我想创建以下函数的"可变"版本:

let InternalArrDiffMax (s : 'T []) (diff : 'T -> 'T -> 'C) =
    s
    |> Array.mapi (fun i e -> 
        [| for j in i + 1 .. s.Length - 1 -> diff e s.[j] |]
        |> Array.maxBy (fun n -> n))
    |> Array.maxBy (fun e -> e)

由于我不能在没有为其赋值的情况下声明可变变量,我认为还有其他方法可以做到:

let InternalArrDiffMax (s : 'T []) (diffFun : 'T -> 'T -> 'C) =
    let mutable max : 'C = // Generic max of 'C if it makes sense

    for i in 0 .. s.Length - 1 do
        for j in i + 1 .. s.Length - 1 do
            let diff = diffFun s.[i] s.[j]
            if (i = 0 && j = 1) || max < diff then
                max <- diff

    max

这就是为什么我认为我需要一个通用的最大值.

Answer 1

@kaefer的答案为您提供了一个获得最大/最小值的好方法,但对于您的特定用例,我建议您'C option改为使用可变变量,并将其初始化为None.这种方式不需要魔法数字.

let InternalArrDiffMax (s : 'T []) (diffFun : 'T -> 'T -> 'C) =
    let mutable max : 'C option = None

    for i in 0 .. s.Length - 1 do
        for j in i + 1 .. s.Length - 1 do
            let diff = diffFun s.[i] s.[j]
            match max with
            | None -> 
                max <- Some diff
            | Some v when v < diff -> 
                max <- Some diff
            | _ -> ()

    max