F#中的结构相等

问题描述

我有一个包含函数的记录类型:

I have a record type that includes a function:

{foo : int; bar : int -> int}

我希望这种类型具有结构上的相等性.有什么方法可以让我标记在相等性测试中应该忽略bar吗?还是有其他解决方法?

I want this type to have structural equality. Is there some way I can just mark that the bar should be ignored in equality tests? Or is there some other way around this?

推荐答案

请参见Don的博客帖子，特别是自定义平等和比较部分.

See Don's blog post on this topic, specifically the section Custom Equality and Comparison.

他提供的示例与您建议的记录结构几乎相同:

The example he gives is almost identical to the record structure you propose:

/// A type abbreviation indicating we’re using integers for unique stamps on objects
type stamp = int

/// A type containing a function that can’t be compared for equality  
 [<CustomEquality; CustomComparison>]
type MyThing =
    { Stamp: stamp;
      Behaviour: (int -> int) } 

    override x.Equals(yobj) =
        match yobj with
        | :? MyThing as y -> (x.Stamp = y.Stamp)
        | _ -> false

    override x.GetHashCode() = hash x.Stamp
    interface System.IComparable with
      member x.CompareTo yobj =
          match yobj with
          | :? MyThing as y -> compare x.Stamp y.Stamp
          | _ -> invalidArg "yobj" "cannot compare values of different types"

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