From: Charles Oliver Nutter <charles.nutter@...>
Date: 2009-02-27T03:22:53+09:00
Subject: [ruby-core:22549] Re: YASNP (Yet Another Selector Namespace	Proposal)

Austin Ziegler wrote:
>>  obj.<namespace::foo>(bar)
>>
>> where <namespace::foo> means "symbol foo in that namespace", and its
>> correspondence can be modified by (dynamic) method definitions.
> 
> Is there any reason that the above can't be made a valid syntax? I
> realize that we would also want a way to magic it so that we're not
> always having to type <namespace::foo> when we want to apply the #foo
> from namespace to obj, but I think that's part of what's been
> bothering me about this proposal: this seems harder to track down than
> necessary when bug fixing.

This exact syntax as written has a number of problems:

obj.< is a valid call
obj.<namespace is obj < namespace
obj.<namespace::foo is obj < namespace::foo
obj.<namespace::foo>(bar) is obj < namespace::foo > (bar)

Lots of ambiguities. If instead we're talking about a version withing 
angle brackets:

obj.namespace::foo(bar) is already valid syntax, equivalent to
obj.namespace.foo(bar).

> I'm also not sure that file-based lexical scoping is entirely what we
> want. What do we want here:
> 
>    require 'my-namespace'
>    using My::Namespace => String;
>    require 'external-dependency'
>    require 'my-dependency'
> 
> If I'm a library writer, I'm not sure whether I want to have to
> specify the "using My::Namespace" line in each of my internal
> dependencies, but at the same time I don't want such things to go into
> external dependencies, either.

I think the important aspect of this is that it's patching writ small. 
The fact that you specify it only in the files where you need it is a 
key feature.

> I'm not opposed to selector namespaces, but I think I worry a little
> that a lot of the discussion has been focussing on what
> framework/library writers would do���presumably we're advanced
> programmers and won't make silly mistakes���and not a lot of thought as
> to how a facility might be abused.

I think there's actually quite a bit of discussion about how it could be 
abused, but I don't think we're heard a lot of specific examples. Do you 
have one in mind?

- Charlie