扩展 F# 列表模块
我已经向一些 F# 模块（例如 List）添加了一些方便的方法。
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，那么向 List 类型的 Ref 添加一个可变方法怎么样？像这样的东西。
type Ref<'a when 'a :> Microsoft.FSharp.Collections.FSharpList<'a> > with //'
member this.AppendMutate element =
this := element :: !this
或者有什么方法可以限制泛型只接受可变的？
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
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
or is there some way to constrain a generic to only accept a mutable?
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F# 3.1 中现在提供了通用扩展方法：
Generic extension methods are now available in F# 3.1:
不幸的是，似乎不可能将扩展成员添加到封闭构造类型（例如
Ref或Seq）。这也适用于您尝试使用的代码，因为您正在用更具体的类型'a list替换开放泛型'T的泛型参数'Tcode>Ref<'T> 类型。Unfortunately, it doesn't appear to be possible to add extension members to closed constructed types (e.g.
Ref<int>orSeq<string>). This also applies to the code you're trying to use, since you're substituting the more specific type'a listfor the generic parameter'Tof the open genericRef<'T>type.