No argument names in abstract declaration?

This is the typical declaration of an abstract member in F#:

abstract member createEmployee : string -> string -> Employee

You define the argument types but not their names. Without names, how do you tell what each parameter is when you implement the interface? In other words, how do you know if the interface expects to be implemented as 1- or 2-?

1-   member this.createEmployee firstName lastName = ...
2-   member this.createEmployee lastName firstName = ...

Am I looking the problem from a wrong perspective (being开发者_如何学Go used to C#)?

What about:

abstract member createEmployee : firstName:string -> lastName:string -> Employee

?

The syntax for this is super fiddly IMO. I wanted to do this with the parameters as a tuple (like a C# method) and only through trial and error did I find this to work:

    abstract member PutChar : x:int * y:int * c:char * flag:Background -> unit

And this uglier variant also works:

    abstract member PutChar : x : int * y : int * c : char * flag : Background -> unit

Below are things that all felt reasonable but failed with the same error - Unexpected symbol ':' in member definition.:

    // ALL BAD vvv
    abstract member PutChar : (x:int * y:int * c:char * flag:Background) -> unit
    abstract member PutChar : (x:int, y:int, c:char, flag:Background) -> unit
    abstract member PutChar : (x:int) * (y:int) * (c:char) * (flag:Background) -> unit
    // ALL BAD ^^^