抽象类型定义f＃

Question

I am looking to define a couple of types in an interface or abstract class with the implementation left unspecified. I then want to inherit from this interface in another, so that i can specify my methods in interface2 with the types that were defined in the first interface.

Eg:

type Interface1 =
      type MyType1
      type MyType2

type Interface2 =
      inherit Interface1
      abstract member method1 : MyType1*MyType2 -> int


Module MyModule =

The idea is that i want the module to then implement interface2, so it should implement MyType1 and MyType2, and method1.

The reason i'm not doing all this in a signature file is because i want to be able to implement type1 and 2 in c# as well, but implementing Interface1.

Can anyone help me with this?

Answer 1

I think what you really want is to use generics:

type Interface2<'T1,'T2> =
      abstract member method1 : 'T1*'T2 -> int

You don't need Interface1 at all here. Then if have Type1 and Type2 implemented in C# (or in F# for that matter), you C# class can inherit from Interface2<Type1,Type2> and you're all set.

Edit: If I've understood your comment correctly, you want to set some constraints on 'T1 and 'T2 such that they implement specific interfaces. The generic names of all this ( 'T1 , Type1 , and so on) is starting to confuse me, so I'm going to use specific names for an example. Let's say that you have a generic IKeyboard interface and a generic IMouse interface, and you want your library's users to implement a specific keyboard and mouse class for your method. In other words, the 'T1 type above must derive from IKeyboard , and the 'T2 type above must derive from IMouse . In that case, type constraints are what you're looking for:

type IKeyboard = class end
type IMouse = class end

type IInputDevices =
    abstract member getInput<'K,'M when 'K :> IKeyboard and 'M :> IMouse> : 'K*'M -> int