扩展F#列表模块 [英] Extending F# List Module

问题描述

我已经在一些F#模块(例如List)中添加了一些方便的方法.

I've been adding a few handy methods to some of the F# modules such as List.

type Microsoft.FSharp.Collections.FSharpList<'a> with          //'
    static member iterWhile (f:'a -> bool) (ls:'a list) = 
        let rec iterLoop f ls = 
            match ls with
            | head :: tail -> if f head then iterLoop f tail
            | _ -> ()
        iterLoop f ls

我想知道是否可以添加突变?我知道List是不可变的，那么如何向List类型的Ref添加可变方法.像这样的东西.

and i'm wondering if it's possible to add mutation? I know List is immutable so how about adding a mutable method to Ref of type List. Something like this.

type Ref<'a when 'a :> Microsoft.FSharp.Collections.FSharpList<'a> > with //'
    member this.AppendMutate element =
        this := element :: !this

还是有某种方法可以限制泛型只接受可变的?

or is there some way to constrain a generic to only accept a mutable?

推荐答案

通用扩展方法现在在F#3.1中可用:

Generic extension methods are now available in F# 3.1:

open System.Runtime.CompilerServices

[<Extension>]
type Utils () =
    [<Extension>]
    static member inline AppendMutate(ref: Ref<List<'a>>, elt) = ref := elt :: !ref

let ls = ref [1..10]

ls.AppendMutate(11)

printfn "%A" ls

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