Re: Matz says namespaces are too hard to implement - why?

Robert Klemme wrote:
2007/12/22, Stefan Rusterholz <apeiros@xxxxxxx>:
But I think I begin to see a thought mistake. I guess I have
to think about it a bit :-/

Actually that fits well with what I was going to suggest: it seemed to
me that you did not have yet fully made up your mind what you want.
:-) I doubt though that a lexical solution would be as useful as a
call stack scoped one.

Ditto, though I'm not a fan of selector namespacing yet anyway.

Also, Charles, maybe implementation implications for lexical scoped
changes might be less dramatic but wouldn't they still impose a
performance penalty at runtime? I mean, the issue of checking would
not change whether it's dynamically or lexically scoped. And there
must be a penalty because of Ruby's dynamic nature, i.e. since it's
not compiled you cannot decide at compile time which version of a
method needs to be invoked. When I think about it it may even make
implementation more difficult, because then the set of current methods
changes even more (i.e. when you redefine a method in a namespace and
invoke that method from another method invoked in that namespace the
old definition would apply again; this also imposes the interesting
question if recursion with redefined methods is still possible... :-))
A lot of interesting problems to solve. :-)

Yes, lexically scoped namespaces would have the same performance
implications call-stack scoped namespaces iff they were applied
dynamically at runtime. If they were applied statically at parse time,
via a keyword or other syntax, the overhead of checking for a namespace
would be limited to specific chunks of code:

(assume "namespace" is a keyword)

my_string.rb:
class StringDecorate
def foo
"woohoo!"
end
end

foo.rb:
namespace String => StringDecorate {
"".foo # => "woohoo!"
}
"".foo # => error

So the idea here is that since namespace is a keyword, at parse or
compile time everything inside the block would be decorated with
namespace-checking logic. And more importantly, everything outside the
block would remain blissfully unaware of namespace checking at all.

But this is still predicated on the idea that lexically-scoped
namespacing is actually useful.

- Charlie

.

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