[nem-en] Extension methods (was Re: My thoughts on Nemerle)

[Alejandro Serrano]

I have decided to split the conversation because it was starting to 
become confusing.

> > About specifying "this", the only problem I see is that then, on the
> > method code, you have to substitute all references of this with the
> > actual parameters, which I find really painful (and on my point of view,
> > non-sense)

>
> Ah, does it mean that this "extension" parameter is refered to as 'this'? Like:
> module Ex {
>    public ListSplit (this x : string) : list [char] {
>        List.FromArray (this.Split())
>    }
> }


Well, the reason underneath the use of only [Extension] in methods is 
that it would not require any modification to the compiler, nor any 
macro. Indeed, Microsoft C# Compiler, just translates

public static Method (this string s) { ... }

to

[System.CompilerServices.ExtensionAttribute()]
public static Method (string s) { ... }

Where Extension is a custom attribute already defined in the 
System.Query library. We will have to wait until Mono gmcs can compile 
the System.Query library, or use my own-compiled one or Microsoft's one.
Because of it, extension parameters can only be used in first place, 
because that is what the [Extension] attribute states: hey! I'm really a 
method who is extending my first parameter type! Even more, in VB.NET no 
actual syntax will be held for extension methods, but appending the 
attribute.

[Extension] public static Method (s : string) { ... } is quite well at 
my point of view

About how to include extension methods, after all this discussion, I've 
seen we cannot be sure that only a class will be used for extension 
methods, so I think the best way to go is to allow both "using X" on 
classes and namespaces.

		
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